How Many Solar Panels Do I Need? Our One-Stop Guide

The all-important question to ask before purchasing solar panel technology is how many solar panels do I need? Unfortunately, there is not one simple answer to this question as it relies on several different variables.

To meet the energy needs of the average American household you are likely to require the following:

Roughly 15–18 solar panels
5 kW worth of power
An available budget of at least $5,000
Roughly 224 sq. feet of available roof space

However, there are many areas you must consider when installing a solar system in order to determine the precise number of panels required. We are going to cover all of them over the course of this guide.

The main factors that impact the number of solar panels needed to meet your energy requirements include but are not limited to these considerations:

The efficiency of your solar panels
The type of solar panels you use
How accurate your energy calculations are
The number of people who live in your house
The location of your house
The size of your house
The number of electronic items in your house
Your energy consumption per year

There are many other areas to consider that may impact the number of panels that you need to purchase too. Today’s aim is to give you a comprehensive overview of absolutely every detail you need to take into consideration to be able to determine exactly how many solar panels you will need to power your chosen technology. Read on for everything you need to know.

1. How Efficient Is a Solar Panel and Why Does This Matter?
2. The Efficiency Rating of Different Solar Panels and How This Impacts How Many Solar Panels Needed
3. How to Calculate Your Own Solar Panel Estimate to Understand How Many Solar Panels Do You Need?
4. How Many Solar Panels Do I Need for a Family of 4 or More?
5. How Many Solar Panels Do I Need to Power a House?
6. What Is the Current Efficiency of Solar Panels Based on Their Roof Position?
7. How Many Peak Sun Hours Are There in the United States?
8. How Many Solar Panels Do I Need in America?
9. How to Size Solar Panels for Your Home
10. How Many Solar Panels Do I Need for Common Household Products?
11. How to Calculate Your Own Solar Panel Estimate for Other Locations Including RVs and Sheds
12. How Many Solar Panels Does an RVer Use and How Many Solar Panels Do You Need on a Boat?
13. How Many Solar Panels Are Required to Charge a 12 Volt Battery?
14. Other Factors That Can Impact the Number of Solar Panels You Need
15. What Is the Average Temperature of the United States & Highest Recorded Temperature Per State?
16. How Efficient Are Solar Panels Over the Years & What Is the Average Lifespan of a Solar Panel?
17. Our Top 3 Space Saving, High Output Solar Panels
18. 3. RICH SOLAR 100 Watt 12 Volt Monocrystalline Solar Panel
19. 2. Newpowa 2 Piece 100W Polycrystalline Photovoltaic PV Solar Panel
20. 1. Renogy 100 Watts 12 Volts Monocrystalline Solar Starter Kit
21. Frequently Asked Questions
22. Conclusion

How Efficient Is a Solar Panel and Why Does This Matter?

Even though all solar panels work in the same way, it is their efficiency rating that really determines how many of them you are going to need in conjunction with their power output capacity.

Solar panel efficiency impacts the following areas:

The amount of power that you are able to harness
The number of panels that you will require in order to meet your energy needs
The overall cost of your system

You will need to factor the efficiency rating percentage of your solar panels into your calculations when trying to determine how many panels you need to purchase. Over the course of this guide, we will provide you with as much information as possible about how to make accurate calculations and also plenty of quick reference tables for those who do not want to take the time to calculate their needs to the exact number.

The Efficiency Rating of Different Solar Panels and How This Impacts How Many Solar Panels Needed

Not all solar panels are created equal. The golden efficiency standard for any solar panel is 24%. What this means is that 24% of all of the available photon rays being emitted by the sun are absorbed by your solar cell array.

This in turn leads to you achieving the maximum possible energy uptake and therefore the highest level of energy efficiency. When this 24% gold standard is not met, problems can begin to arise.

Consider the following before performing your energy calculations and asking the question, how many solar panels do I need for my home?

Some solar panels may be more expensive than others, but if their efficiency is higher, then the extra cost is returned in the form of more usable energy over time.
Should you only have a minimal amount of spare roof space, you will need to use the highest powered and most efficient solar panels possible to maximize all available space and therefore your potential energy uptake.

Solar panel efficiency ratings can depend on a number of different factors including build quality. Here are some of the factors that are not associated with build quality:

Where your property is located (For example, is it south facing?)
The location of your solar panels
Ineffective installation
The number of daylight hours in your area per year

Assuming that you have a south-facing property that is located in an area that has access to an abundance of sunshine throughout the year and that your panels are being installed by a qualified professional, then your efficiency capacity is largely going to rely on the type of solar panels that you purchase.

Understanding the different panel varieties will help you to understand how many solar panels are needed to power a house. There are three different varieties of solar panels:

Monocrystalline Solar Panels

Key facts:

The most efficient type of solar panel
Made from one singular sheet of silicon crystal
The most expensive variety of solar panel

Monocrystalline solar panels are formed out of a single sheet of silicon and were the first widely available variety of solar panel available for purchase.

Mono panels are able to achieve up to a maximum of 24–26% efficiency (The average efficiency rating for high-end mono panels is between 21–24%.) because of the fact that their surface features no breaks or lines as a result of only one component being used to formulate them.

This is in contrast to other varieties of solar panels that have been created using a combination of several different silicon crystal pieces. Hence, there are natural breaks in the sheet material of these panels.

Polycrystalline Solar Panels

Key facts:

The second most efficient type of solar panel (roughly 85% as effective as monocrystalline)
Made out of several fragments of silicon crystal combined together to form one sheet
Slightly cheaper than monocrystalline panels

Polycrystalline solar panels offer a (usually) more affordable alternative to monocrystalline panels. They have been formed out of several fragments of silicone crystal that have been fused together to form one whole sheet of conductive solar panel.

The downside to using sheets made out of polycrystalline solar technology is the fact that their multi-crystal composition leads to natural breaks in the surface of the panel itself, thus reducing their effectiveness in the process compared to single-sheet monocrystalline panels.

On average, the overall absorption percentage for poly panels is around a maximum of 22% compared to the 26% maximum that monocrystalline panels can achieve. This in turn means that you need to use more of them in order to meet your large-scale energy needs.

Thin Film (Flexible) Solar Panels

Key facts:

The most inefficient type of solar panel (usually has an efficiency rating of roughly 14%)
Features conductive silicon cells on a thin laminate sheet that is flexible enough to be placed in a wide variety of locations
The cheapest variety of solar panel

With a maximum absorption rating potential of around 14%, thin film solar panels are easily the most inefficient panel variety available, but it is actually the versatility allowed by their construction that makes them such an enormous draw. Thin film panels are flexible enough to be placed in locations where it would otherwise be completely impossible to install solar panel technology. Examples include boat hulls and even awkward and angular outcroppings on buildings.

This actually means that you are able to introduce more flexible solar panels into certain locations than you would be able to when using either monocrystalline or polycrystalline varieties.

As such, you can still achieve the same level of energy output even when you are trying to meet the energy requirements of a house simply through using a higher volume of panels. If you happen to have a building with a particularly awkward shape, then this may even be your most viable option.

Given that efficiency ratings are ultimately the underlying figure required to determine how many solar panels are needed to power a house and make a precise calculation in regards to the specific energy output you will be able to achieve, it is very important that you weigh this consideration while trying to make a final purchase decision.

Of course, knowing the efficiency rating of your chosen solar panel model is pointless if you do not know what your energy requirements are. As this is the starting point, let’s dive into this area a little further.

How to Calculate Your Own Solar Panel Estimate to Understand How Many Solar Panels Do You Need?

As long as you are able to make an accurate energy calculation, then you are going to be able to determine precisely how many solar panels are needed to meet your needs.

There is a simple formula for figuring this out, which is as follows:

Take your device wattage (also known as watts) and multiply it by the number of hours your device is used for per day. This will provide your total watt-hours (Wh) per day for said item. You will need to do this for every electrical item in your home.
Now, take your total device usage in watts for each item and combine them together to get your daily total energy usage in kW (kilowatts).
Next, take your daily usage (measured in kW) and times it by 30 (representing the average number of days in a calendar month) to find out the approximate monthly usage (kW/month) for your household items.

If you are the kind of person that likes to be as specific as possible, then this process is the only way that you are going to be able to get a completely accurate reading that you can then use to determine how many solar panels you are going to require for your home or any other location (garden shed, outhouse, RV, etc.).

How to Calculate How Many Solar Panels Needed Easily for a Family of 4

An average American family of 4 consumes between 877–900 kilowatt hours per month. This means that they use roughly 30 kilowatt hours per day.

In order to find out your average annual energy requirements for a family of 4, you simply need to perform the following calculation:

Take the number 900
Multiply it by 12
This will give you a figure of 10,800

This means that the average American family will require a solar system that is capable of producing 10,800 kilowatt hours per year.

Other Ways to Measure Energy Consumption for Homes, RVs, Boats, and Sheds

There are also several other ways to measure your energy consumption without performing precise calculations.

Checking previous energy bills
Using your home utility meter readings
Installing a smart meter or smart monitoring technology

We will shortly show you a chart to give you a rough idea about what size system you will need for different family sizes and their associated costs, but you might want to consider the following points too.

#1. Use Your Previous Energy Bills

Rather than performing time consuming calculations, you could actually just check over your energy bills for the past 12 months and figure out the monthly average based on the final monthly energy consumption during each 30-day period.

This is a great way to understand exactly how much energy you typically use over the course of a year. Unless you are planning to make any drastic changes or add any new residents to your household, the next 12 months and all future readings are likely to be around the same level too. You can use your monthly average to determine what size of solar system you are likely to require.

#2. Check Your Household Energy Meter

Every house has a standard meter that displays how much energy they consume over the course of various periods depending on how sophisticated the built-in technology is.

This is a fantastic way to dive into serious detail about your energy consumption and find out exactly how much you use per month and at different times of the year. Simply through checking your household meter, you can easily determine how much energy you typically consume over the course of 12 months and base your solar panel system size requirements on this.

#3. If You Are an RV or Boat Owner, Use a Smart Meter

Just like with your home, your RV or boat is powered from a central generation source. This means that it can be monitored in exactly the same way that your home system can. The best way to do this is to install a smart meter so that you can monitor your energy consumption at any time you like. Once installed, allow your meter to read your usage over the course of several months in order to determine precisely how much power you use on average per trip, per week, and per month.

You can then use this data to calculate the size of the solar panel system that you will require in order to meet the energy requirements of your “home away from home.” It is worth keeping in mind that you should also consider installing a smart meter in your home because they can give the most accurate and reliable energy consumption readings at any time.

#4. For Smaller Locations, The Time-Consuming Calculation Process Might Be Less Time Consuming

If you are a boat, shed, or RV owner, consider that calculating your energy requirements based on individually calculating the combined wattage of your appliances is likely to be a much easier process than it is for someone doing the same with a home.

This is because the internal space is much smaller. Accordingly, there should be less items to calculate. As such, performing the calculation process that we mentioned in the last section is also a great way to achieve a realistic energy consumption figure for these locations.

Later on in this guide, we have listed the individual power output of almost every common household (or boat/RV) item so that you can easily add up your power requirements with a quick glance if you would prefer not to look on the back of the items for their individual wattage ratings.

How Many Solar Panels Do I Need for a Family of 4 or More?

On average, a family of 4 will require these specifications:

15–18 solar panels
Roughly 5 kW worth of power
224 sq. feet of available roof space

To cater to any family, we will now show you a chart that displays how much power solar panel systems of varying sizes are able to produce on average per day and the different family sizes that they can typically provide for.

System Size:	Average Number of Panels Needed:	Average Cost of System:	Average Family Size or Residents Catered to:
4 kW	13	$2,600–$4,000	2–4
5 kW	15	$3,600–$5,000	4–5
6 kW	18	$4,800–$6,000	5–6
7 kW	25	$5,400–$7,000	6–7
8 kW	30	$6,500–$8,000	7–8
10 kW	35	$8,600–$10,000	8–9
12 kW	40	$10,000–$12,000	9–10
15 kW	50	$12,000–$15,000	10–11
20 kW	60	$18,000–$20,000	11–12

The above calculations are based on a “good” industry average figure of between $0.80 to $1.00 per watt. This is roughly how much you can expect to pay for a variety of different sizes of solar panel systems at a quick glance. Do not forget that these estimates are largely based on prefabricated solar panels of the variety that you would purchase from an established solar retailer.

If you have reasonable DIY knowledge, then it may prove viable to create your own solar panels to make considerable cost savings. How-to guides (like the immensely popular Backyard Revolution) can show you how to do this step by step.

To make your life as easy as possible, we are now going to provide you with some separate guides to help you to clearly identify the number of panels that will be required to meet your energy needs regardless of where you are planning to install them. The aim of these guides is to give the most specific calculations possible to ensure that you do not waste a cent of your hard-earned money.

How Many Solar Panels Do I Need to Power a House?

How many solar panels do I need for my home? This is perhaps the most common question asked about solar panels.

Certain factors impact the number of solar panels needed for a house:

The tilt angle of the solar panels
The direction your roof is facing
The number of peak daylight hours in your area

Ultimately, although the majority of prospective solar technology users have the goal of eventually being able to go completely off-grid and meet all of their energy requirements purely through the installation of solar technology, this is only going to be possible if you can meet specific installation conditions.

The first important factor to consider is the angle of your solar panels, followed by the direction your roof is facing. It must be south facing in order to absorb the highest possible amount of sunlight per day. Check out the following quick reference table to gain a better understanding about how the direction of your roof and panel tilt angle can impact your ability to maximize your photon ray uptake per day.

What Is the Current Efficiency of Solar Panels Based on Their Roof Position?

Panel Tilt Angle (in Degrees):	Directly West-Facing Roof Photon Ray Access Efficiency:	Directly South-Facing Roof Photon Ray Access Efficiency:	Directly East-Facing Roof Photon Ray Access Efficiency:
0	84%	84%	84%
10	84%	91%	84%
20	82%	96%	82%
30	81%	100%	81%
40	78%	100%	78%
50	74%	98%	74%
60	69%	95%	69%
70	64%	89%	64%
80	57%	81%	57%
90	50%	71%	50%

As you can see based on the above chart, it is clear that a directly south-facing roof with a series of panels that have been set at precisely a 40-degree angle will be able to access a maximum of 100% of the sun’s available incoming photon rays.

Even though the most advanced solar technology is still only able to physically harness a maximum of 24–26% of the total number of incoming rays at any one time, having the maximum 100% access is still the only way that you will be able to reach these optimum efficiency figures.

Ideally, both your roof and your solar panels should be placed in such a fashion that they fall in line with these directly south-facing and 30–40-degree panel angle placement ideals. However, all is not lost if this is not the case. If you have a roof that is oriented in a west- or east-facing position (or even a south-facing position but with a series of panels that are not at a 40-degree tilt angle), simply calculate your energy potential requirements based on the following calculation process:

Using 100% as the perfect benchmark, calculate the missing difference between your energy potential rating and 100. For example, if your maximum potential rating is 84%, the missing difference between this figure and 100 is 16.
Times your daily kW rating number by the missing difference percentage. In this instance, you would need to multiply your daily kWh rating by 0.16 to figure out what 16% of your total daily kWh usage would be.
You will then need to add this figure onto your total daily kW figure in order to determine how many extra panels would be needed to achieve the equivalent of the perfect 100% south-facing roof and 40-degree panel tilt angle photon ray access benchmark.

If you had calculated your overall daily needs as being 4 kW, then using the above process and examples, you would simply need to figure out what 16% of 4 kW was (640) and add this figure onto your daily requirement total (4,000) to determine how many surplus panels would be required to achieve your maximum kWh rating based on your roof and panel location and position. In this instance, you would need to achieve a total output of 4,640 kW to make up for the lack of efficiency if you had a photon ray access potential of 84%.

The next part of the equation is to understand how many daylight hours there are in your area. Assuming that you have a directly south-facing roof and a 40-degree tilted series of solar panels, you are still only going to be able to harness as much energy as you freely have available during the day based on where you live. The following chart gives an overview of the number of peak sunlight hours available in different states in the USA to give you a better understanding.

How Many Peak Sun Hours Are There in the United States?

State	Minimum Number of Peak Sunlight Hours	State	Minimum Number of Peak Sunlight Hours
Alabama	4.5	Nebraska	4.9
Alaska	2.4	New Hampshire	4.0
Arizona	6.5	New Jersey	4.2
Arkansas	4.9	Nevada	6.2
California	5.8	New Mexico	7.0
Colorado	5.3	New York	3.5
Connecticut	4.0	North Carolina	5.0
Florida	5.4	North Dakota	4.5
Georgia	4.7	Ohio	3.9
Idaho	5.1	Oklahoma	5.5
Illinois	4.3	Oregon	3.7
Indiana	4.1	Pennsylvania	4.0
Iowa	4.2	Rhode Island	4.3
Kansas	5.2	South Carolina	4.4
Kentucky	4.1	South Dakota	5.0
Louisiana	4.9	Tennessee	4.2
Maine	4.0	Texas	5.2
Michigan	3.8	Utah	5.7
Massachusetts	4	Vermont	3.8
Maryland	4.4	Virginia	4.6
Minnesota	4.3	Washington	3.3
Mississippi	4.9	Wisconsin	4.3
Missouri	4.9	Wyoming	5.2
Montana	4.5

On average, a solar panel operating at the maximum efficiency level (24–26% with a monocrystalline system) is able to produce its maximum energy rating every hour. For example, a 100-watt panel can produce 100 watts per hour, and a 300-watt panel can make 300 and so on.

Assuming that you have a south-facing roof with a panel that has a 40-degree tilt angle and therefore are accessing 100% of the sun’s incoming rays, you are likely to be able to achieve the following output levels per hour when using different sizes of 100-watt panel systems.

100-Watt Panel System Size:	3-Peak-Daylight-Hour Output:	4-Peak-Daylight-Hour Output:	5-Peak-Daylight-Hour Output:	6-Peak-Daylight-Hour Output:
1X100-Watt Panel	300 watts per day	400 watts per day	500 watts per day	600 watts per day
3X100-Watt Panels	900 watts per day	1200 watts per day	1500 watts per day	1800 watts per day
5X100-Watt Panels	1,500 watts per day	2,000 watts per day	2,500 watts per day	3,000 watts per day
7X100-Watt Panels	2,100 watts per day	2,800 watts per day	3,500 watts per day	4,200 watts per day
9X100-Watt Panels	2,700 watts per day	3,600 watts per day	4,500 watts per day	5,400 watts per day
12X100-Watt Panels	3,600 watts per day	4,800 watts per day	6,000 watts per day	7,200 watts per day
15X100-Watt Panels	4,500 watts per day	6,000 watts per day	7,500 watts per day	9,000 watts per day
18X100-Watt Panels	5,400 watts per day	7,200 watts per day	9,000 watts per day	10,800 watts per day
20X100-Watt Panels	6,000 watts per day	8,000 watts per day	10,000 watts per day	12,000 watts per day

And if you are planning to use several 500-watt system kits (consisting of 5X100-watt solar panels each), here are the applicable output results.

500-Watt Panel System Size:	3-Peak-Daylight-Hour Output:	4-Peak-Daylight-Hour Output:	5-Peak-Daylight-Hour Output:	6-Peak-Daylight-Hour Output:
1X500-Watt System Kit	1,500 watts per day	2,000 watts per day	2,500 watts per day	3,000 watts per day
3X500-Watt System Kits	4,500 watts per day	6,000 watts per day	7,500 watts per day	9,000 watts per day
5X500-Watt System Kits	7,500 watts per day	10,000 watts per day	12,500 watts per day	15,000 watts per day
7X500-Watt System Kits	10,500 watts per day	14,000 watts per day	17,500 watts per day	21,000 watts per day
9X500-Watt System Kits	13,500 watts per day	18,000 watts per day	22,500 watts per day	27,000 watts per day
12X500-Watt System Kits	18,000 watts per day	24,000 watts per day	30,000 watts per day	36,000 watts per day
15X500-Watt System Kits	22,500 watts per day	30,000 watts per day	37,500 watts per day	45,000 watts per day
18X500-Watt System Kits	27,000 watts per day	36,000 watts per day	45,000 watts per day	54,000 watts per day
20X500-Watt System Kits	30,000 watts per day	40,000 watts per day	50,000 watts per day	60,000 watts per day

These figures are based on all of the panels in your system carrying an efficiency rating of between 24–26%. For a system that consisted of flexible panels for example, it would be wise to multiply these numbers by two to make up for the lower efficiency rating as it would be almost half of that of monocrystalline solar panels.

Using the above chart and the daylight hours in your state/area chart, we can effectively summarize the minimum number of panels that you require to meet your energy needs.

The average American household uses 900 kWh per month (30 kWh per day). As such, if you use individual 100-watt panels or 500-watt monocrystalline solar panel system kits, this is how many you will require to meet the American average depending on where you live and the minimum peak sunlight hours in your area.

How Many Solar Panels Do I Need in America?

State:	Minimum Number of Peak Sunlight Hours:	Number of 100-Watt Solar Panels Needed to Meet the National Average Daily Requirement:	Number of 500-Watt Solar Panel Kits Needed to Meet the National Average Daily Requirement:	Average Panel Cost to Cover the National Average Daily Requirement:
Alabama	4.5	68	14	$6,800–$7,800
Alaska	2.4	126	25	$12,000–$13,000
Arizona	6.5	48	10	$4,800–$5,800
Arkansas	4.9	62	13	$6,200–$7,500
California	5.8	52	11	$5,200–$6,200
Colorado	5.3	78	16	$7,800–$8,800
Connecticut	4.0	76	15	$7,600–$8,600
Florida	5.4	56	11	$5,600–$6,400
Georgia	4.7	64	13	$6,400–$7,200
Idaho	5.1	60	12	$6,000–$6,800
Illinois	4.3	70	14	$7,000–$7,800
Indiana	4.1	74	15	$7,400–$8,300
Iowa	4.2	72	15	$7,200–$8,300
Kansas	5.2	58	12	$5,800–$6,400
Kentucky	4.1	74	15	$7,400–$8,300
Louisiana	4.9	62	13	$6,200–$6,900
Maine	4.0	76	15	$7,600–$8,400
Michigan	3.8	80	16	$8,000–$8,900
Massachusetts	4.0	76	15	$7,600–$8,400
Maryland	4.4	70	14	$7,000–$7,700
Minnesota	4.3	68	14	$6,800–$7,500
Mississippi	4.9	62	13	$6,200–$6,900
Missouri	4.9	62	13	$6,200–$6,900
Montana	4.5	70	14	$7,000–$7,700
Nebraska	4.9	62	13	$6,200–$6,900
New Hampshire	4.0	76	15	$7,600–$8,300
New Jersey	4.2	72	15	$7,200–$8,300
Nevada	6.2	50	10	$5,000–$5,700
New Mexico	7.0	44	9	$4,400–$5,100
New York	3.5	86	17	$8,600–$7,300
North Carolina	5.0	60	12	$6,000–$6,800
North Dakota	4.5	70	14	$7,000–$7,700
Ohio	3.9	78	16	$7,800–$8,500
Oklahoma	5.5	56	11	$5,600–$6,200
Oregon	3.7	82	17	$8,200–$9,000
Pennsylvania	4.0	76	15	$7,600–$8,300
Rhode Island	4.3	70	14	$7,000–$7,700
South Carolina	4.4	69	14	$6,900–$7,700
South Dakota	5.0	60	12	$6,000–$6,800
Tennessee	4.2	72	15	$7,200–$8,300
Texas	5.2	58	12	$5,800–$6,600
Utah	5.7	54	11	$5,400–$6,100
Vermont	3.8	80	16	$8,000–$8,800
Virginia	4.6	66	13	$6,600–$7,300
Washington	3.3	92	19	$9,200–$10,000
Wisconsin	4.3	70	14	$7,000–$7,700
Wyoming	5.2	58	12	$5,200–$6,000

For those using polycrystalline or thin film solar panels, this is how many panels you are likely to require in order to meet your daily household energy requirements.

State:	Minimum Number of Peak Sunlight Hours:	Number of 100-Watt Polycrystalline Solar Panels Needed to Meet the National Average Daily Requirement:	Number of 100-Watt Thin Film Solar Panels Needed to Meet the National Average Daily Requirement:
Alabama	4.5	78	156
Alaska	2.4	145	290
Arizona	6.5	55	110
Arkansas	4.9	71	142
California	5.8	60	120
Colorado	5.3	90	180
Connecticut	4.0	87	174
Florida	5.4	64	128
Georgia	4.7	74	148
Idaho	5.1	69	138
Illinois	4.3	81	162
Indiana	4.1	85	170
Iowa	4.2	81	162
Kansas	5.2	67	134
Kentucky	4.1	85	170
Louisiana	4.9	71	142
Maine	4.0	87	174
Michigan	3.8	92	184
Massachusetts	4.0	87	174
Maryland	4.4	80	160
Minnesota	4.3	78	156
Mississippi	4.9	71	142
Missouri	4.9	71	142
Montana	4.5	80	160
Nebraska	4.9	71	142
New Hampshire	4.0	87	174
New Jersey	4.2	81	162
Nevada	6.2	58	116
New Mexico	7.0	51	102
New York	3.5	99	198
North Carolina	5.0	69	138
North Dakota	4.5	81	162
Ohio	3.9	90	180
Oklahoma	5.5	64	128
Oregon	3.7	94	188
Pennsylvania	4.0	87	174
Rhode Island	4.3	80	160
South Carolina	4.4	79	158
South Dakota	5.0	69	138
Tennessee	4.2	83	166
Texas	5.2	67	134
Utah	5.7	62	124
Vermont	3.8	71	142
Virginia	4.6	76	152
Washington	3.3	106	212
Wisconsin	4.3	81	162
Wyoming	5.2	67	134

The costs for these systems will be similar to that of a monocrystalline system given the considerably larger volume of panels required to power a house, regardless of them costing less per unit. A thin film system would certainly be likely to be the cheapest, however. The ultimate aim of the game is to try to achieve your energy requirements through the use of as few solar panels as possible so that you do not take up all of your available roof space.

Realistically, the only way that you are going to be able to do this is via the use of high output panels (300–400 watts) as opposed to lower output panels (100 watts). Although this is only a rough guide, the following chart will give you a fairly accurate idea of how much roof space you are likely to take up with different sizes of solar panel systems consisting of 100-watt panels.

What Size Solar System for an Average Home in Square Feet?

Overall System Size in KWh:	Low Efficiency System in Sq. Feet (Thin Film):	Medium Efficiency System in Sq. Feet (Polycrystalline):	High Efficiency System in Sq. Feet (Monocrystalline):
5 kW	306	254	224
10 kW	612	508	448
15 kW	918	763	672
20 kW	3,242	1,016	896
25 kW	1,572	1,270	1,120
30 kW	1,908	1,524	1,344

Whether you wish to use some of the quick reference charts above to determine how many solar panels you require and how much space they are likely to take up at a quick glance or are the type of person who likes to perform the calculations yourself, you definitely have all of the information you could ever need here in order to be able to answer this all-important question. How many solar panels do I need for my home?

For those who prefer to take a slightly simpler approach and do not wish to determine precisely how many panels are needed to the exact number, you can always use the following chart to help you determine how many panels will be required based purely on your home size. Here are the average panel requirements based on the average energy consumption for properties of various types in the USA based on an average of 4.5 peak daylight hours per day.

How to Size Solar Panels for Your Home

Property Type:	Average Annual Energy Consumption in KWh:	Average Number of 500-Watt Solar Panel Kits Needed:	Total Output of System (Monocrystalline):
Large Detached Property:	10,800	14	31 kWh per day
Bungalow:	6,480	8	18 kWh per day
Apartment	5,400	7	16 kWh per day

How Many Solar Panels Do I Need for Common Household Products?

All of your appliances and electrical items carry a different wattage rating that can be used to determine how much energy they require over the course of a year for operation.

The largest items (washing machines, tumble dryers, water heaters) are the most energy hungry.
Some of your items will need to be powered constantly, 365 days per year.
The energy efficiency rating of your items will determine how much power they use.

In order to find out how many watts it takes to power a wide array of typical household items over the course of a year, simply take a look at the following chart if you would prefer to try and estimate your energy consumption via this means rather than checking the wattage rating of every individual item in your home.

Household Item:	Average Annual Energy Consumption in KWh:	Average Usage Period Per Day:	Number of 500 W Solar Panel Kits (5X100 W Panels) Needed on Average to Power Throughout the Year:
Fridge	300–600 kWh	Continuous, 365 days	1–2
Dishwasher	300–400 kWh	5 days per week	1
Coffee Machine	42–60 kWh	10 mins per day, 335 days per year	<1
Cooker Hood	25–40 kWh	40 mins per day, 335 days per year	<1
Microwave Oven	90 kWh	1.5 hours per week over 48 weeks per year	<1
Electric Oven	162–230 kWh	1.5 hours per week over 48 weeks per year	1
Toaster	44–60 kWh	1 hour every 10 days across 48 weeks per year	<1
Food Processor/Blender	15–22 kWh	2 hours every 10 days across 48 weeks per year	<1
LCD TV	241–400 kWh per year	4 hours per day across 335 days per year	1
LED TV	54–100 kWh per year	4 hours per day across 335 days per year	<1
Low-Energy Light Bulb	20–30 kWh per year	5 hours per day across 335 days per year	<1
Video Game Console	8–90 kWh per year	387 hours of average use per year	<1
TVD Decoder	277–350 kWh per year	365 days of continuous use	1
Singular Halogen Lamp	503–600 kWh per year	5 hours per day across 335 days per year	1–2
Stereo System	53–70 kWh per year	4 hours per day across 335 days per year	<1
Window AC	1445–2,000 kWh per year	6 hours per day across 365 days per year	2–3
Tumble Dryer	192–300 kWh per year	2 hours per week across 32 weeks per year	1
A+++ Energy Efficient Washing Machine	173 kWh per year	4 hours per week across 48 weeks per year	1
Iron	260–350 kWh per year	5 hours per week across 48 weeks per year	1
Vacuum Cleaner	70–90 kWh per year	2 hours per week across 48 weeks per year	<1
Ceiling Fan	288 kWh per year	5 hours per week across 48 weeks per year	1
Hot Water Immersion Heater	432–600 kWh per year	3 hours per week across 48 weeks per year	1–2
LED Light Bulb	2 kWh per year	6 hours per week across 48 weeks per year	<1
Desktop Computer	36.5–50 kWh per year	1 hour per day across 365 days per year	<1
Electric Shaver	0.78–2 kWh per year	1 hour per week across 365 days per year	<1
Hair Dryer	328–500 kWh per year	30 minutes per day across 365 days per year	1–2
Tablet Charger	1–1.5 kWh per year	3 hours per day across 365 days per year	<1
Table Fan	7.3–11 kWh per year	2 hours per day across 365 days per year	<1

The above figures assume that you have eco-friendly technology that carries a minimum of an “A” energy rating. As a rule of thumb, you should allocate one panel per every three items that require less than one panel to power them

How to Calculate Your Own Solar Panel Estimate for Other Locations Including RVs and Sheds

In order to calculate your own solar cell requirements for a number of different locations excluding your home, you can either take the precise route or the general route as before.

It is important to know these considerations.

You can add up your energy requirements for boats, RVs, and sheds in the same way as you can for a house.
Boat, RV, and shed energy requirements range anywhere from 80% of the requirements of an average-sized house for some RV models all the way down to 20% for sheds depending on their size.
Batteries play an important part in the energy requirements of RVs and boats particularly.
You will need to understand how much usable power you can source from certain batteries and also how much solar power is required to “feed” them.

In order to generate the most pinpoint accurate figure, simply add up the wattage value of the items you wish to power in your chosen location in order to determine their annual usage. Following this, you can then relate that figure directly to the number of panels needed to operate them.

A relatively easy way to calculate is to observe the number of panels needed across various different percentage ranges based on the national average of 900 kWh per month (10,800 per year).

How Many Solar Panels Does an RVer Use and How Many Solar Panels Do You Need on a Boat?

Annual Usage Percentage (Based on the American National Average of 10,800 kWh per Year):	Average Number of 500-Watt Panel Kits (Consisting of 5X100 W Panels) Required:	Average System Cost:
80% (an RV or boat for example)	11	$5,500
60% (a medium-sized apartment or bungalow for example)	8	$4,000
40% (a workshop for example)	6	$3,000
20% (a garden shed for example)	4	$2,000

Though these percentage ranges are relatively accurate, they are still not pinpoint precise. They are not precise enough for those who wish to calculate their requirements as accurately as possible at least without there being any waste in the process.

Understanding Batteries—The Key to Specific RV and Outhouse Calculations

When using an RV or camper, it is the output of the battery that is really going to determine exactly how much solar power is required to meet your energy requirements.

This is the same if you are powering a workshop or shed too. You are ultimately going to have to generate enough power to be able to effectively recharge and sustain the battery that feeds power into your appliances from your solar panel array.

To make calculating as easy as possible for you, we have compiled a list of various different battery sizes and types in conjunction with the amount (in watts) required to sustain them and also the number of panels that you will need in order to achieve these various wattage outputs too. Please note that every 100 usable battery hours require precisely 1,280 watts worth of power. Various battery types and their power requirements are as follows.

How Many Solar Panels Are Required to Charge a 12-Volt Battery?

Battery Type:	Battery Capacity:	Number of Batteries:	Usable Battery Hours:	Watts Required to Power Battery:	Number of 500-Watt Solar Panel Kits Needed to Power Battery System (Based on an Average of 4.5 Peak Sunlight Hours in Your Area):
Lithium	100 Ah (12 volts)	1	100 Ah	1,280	1
Lithium	100 Ah (12 volts)	2	200 Ah	2,560	2
Lithium	100 Ah (12 volts)	3	300 Ah	3,840	2
Lithium	100 Ah (12 volts)	4	400 Ah	5,120	3
AGM	100 Ah (12 volts)	1	50 Ah	640	1
AGM	100 Ah (12 volts)	2	100 Ah	1,280	1
AGM	100 Ah (12 volts)	3	150 Ah	1,920	2
AGM	100 Ah (12 volts)	4	200 Ah	2,560	2

It is the battery capacity and usable hours that ultimately determine the wattage requirements of your home-based systems too, but in these instances, it is commonly agreed that lithium ion batteries are the best to use for home installations. This means that it is typically less important to explore the different varieties of batteries on offer as it is when outfitting external locations like motorhomes and sheds where you have more leeway.

Other Factors That Can Impact the Number of Solar Panels You Need

Because purchasing solar panels is one of the costliest considerations you will ever make, it is very important that you get the installation process right the first time in order to ensure that none of your hard-earned money is wasted.

There are several factors that can impact the number of panels you require.

The effectiveness of the panel installation process
The weather rating of your panels
The build quality of your panels
The age of your panels if they are used

Though the most important aspect of your panels that is going to determine how many you will need is your annual energy consumption, it is important to understand the several other areas that will play a part in determining how many panels you are going to require over time.

Who Is Going to Install Your Solar Panel

Not all solar panel installations are performed equally, and all it takes is one wrong or misplaced wire in order to render the overall efficiency of your system completely or partially compromised.

Even if your system does not become less effective as a result of a slapdash installation process, the truth is that every valuable percent of your panel efficiency that gets lost means that some of the space on your roof is being wasted and that you are generating less power. This can easily make a 60-panel system operate more like a 45–50 panel system, thus losing you energy and money.

If you are not competent enough at performing DIY projects to be able to install the panels yourself, then make sure that you get a qualified professional to do the job. There is no point in making precise calculations if the panels themselves do not work in the way that they are supposed to.

All this will mean is that you will have to either install more panels than you already have to make up for the lost efficiency or that you will have costly repairs performed on your existing panels if they are not under warranty. Solar panels should realistically be a one-time outlay if you get everything right when they are first installed. Do everything in your power to ensure that this is the case.

The Temperature Rating of Your Solar Panels

Solar panels are usually tested at roughly 77 degrees Fahrenheit to determine whether or not they are able to produce optimal energy in high temperature conditions. Generally speaking, most panels are able to operate at their peak level when they are operating within a temperature range of between 59 and 95 degrees Fahrenheit. Should their temperature exceed this range however, issues can begin to arise.

With some panels facing temperatures of anywhere up to 149 degrees Fahrenheit depending on their location, it is vital that you purchase solar panels that are able to withstand the maximum expected temperature range for your area of residence. You will be able to find out this information by reading through the manufacturer’s handbook that accompanies your panels.

The extent to which solar panel efficiency diminishes above 77 degrees Fahrenheit is known as a coefficiency rating. For our upcoming example, we will use a 0.38% guideline coefficiency rating to help you to understand what kind of impact you may expect to encounter on your energy production potential under extremely hot weather conditions.

The below chart displays the maximum recorded temperatures for each American state so that you can purchase your solar panels according to the maximum limit or as close to it as possible. It also displays the impact that these temperatures would have on the overall efficiency of a 500-watt panel kit.

What Is the Average Temperature of the United States & Highest Recorded Temperature Per State?

State:	Maximum Recorded Temperature (in Fahrenheit):	Potential Impact on a Solar Panel System’s Overall Efficiency (Based on a Coefficiency Rating of 0.38%):
Alabama	112	-13%
Alaska	100	-9%
Arizona	128	-19%
Arkansas	120	-16%
California	134	-22%
Colorado	115	-14%
Connecticut	106	-11%
Florida	109	-12%
Georgia	112	-13%
Idaho	118	-16%
Illinois	117	-15%
Indiana	116	-15%
Iowa	118	-16%
Kansas	121	-17%
Kentucky	114	-14%
Louisiana	114	-14%
Maine	105	-11%
Michigan	112	-13%
Massachusetts	107	-11%
Maryland	109	-12%
Minnesota	115	-14%
Mississippi	115	-14%
Missouri	118	-16%
Montana	117	-15%
Nebraska	118	-16%
New Hampshire	106	-11%
New Jersey	110	-13%
Nevada	125	-18%
New Mexico	122	-17%
New York	109	-12%
North Carolina	110	-13%
North Dakota	122	-17%
Ohio	113	-14%
Oklahoma	122	-17%
Oregon	117	-15%
Pennsylvania	111	-13%
Rhode Island	104	-10%
South Carolina	113	-14%
South Dakota	120	-16%
Tennessee	113	-14%
Texas	120	-16%
Utah	117	-15%
Vermont	105	-11%
Virginia	110	-13%
Washington	118	-16%
Wisconsin	114	-14%
Wyoming	115	-14%

If you have the resources to be able to do so, then based on your panels’ coefficiency rating, you can purchase additional panels to factor in any potential loss of efficiency through temperature extremes.

In order to do this, you would first need to perform the following calculation process.

Take note of your panels’ coefficiency rating as supplied by the manufacturer.
Check the maximum recorded temperature extreme in your state and minus 77.
Multiply the remaining number by your panels’ coefficiency percentage.
This number will reveal the loss of panel efficiency that you may encounter with maximum temperature extremes in your area.

Once you have your coefficiency impact percentage, you can then calculate how many additional panels would be needed to counteract its effect.

In order to determine how many extra panels would be needed, perform the following calculation process.

Take the total number of panels in your system.
Multiply this number by the coefficiency impact percentage of your panel model.
Take this number and add it to your total solar panel number to counteract the difference of the coefficiency impact percentage.

For example, if you were to use a series of 16X500-watt panel kits while living in Ohio and wanted to purchase additional panels to cover the maximum recorded temperature there, you would need to add an additional 14% to the overall number of panels in your system.

As 14% of 16 is 2.24, you would need to add an additional 2 kits (10X100 W panels) to your system in order to counteract the loss of efficiency in temperature extremes.

Your Panel Build Quality and Durability

As we have already stated, purchasing a solar panel system should be a one-time outlay assuming you get everything right the first time. This is where the quality of your panels really comes into play. It is not just about the number of panels you will need in the short term but also the number of panels that you might need to replace in the long term that matters too.

In order to ensure that your panels are going to be able to withstand harsh weather conditions while maintaining their efficiency, always aim to be certain that they feature a solid metal frame and a waterproof rating of IP65.

Always be sure that the included brackets and mounts are made out of solid, hard-wearing metal too. This will massively amplify your chances of never having to purchase more panels after your initial install provided you have them serviced regularly.

The Use of Monitoring Systems and Regular Servicing

Some people see monitoring systems and regular servicing as an unnecessary expense after installing their panels, but the idea of these facets of solar panel maintenance is that they actually save you money in the long term as a result of having to replace less or zero panels.

Monitoring will allow you to see exactly what efficiency level your system is operating at during any given period, meaning that you will notice instantly if there is a fault. Regular servicing can isolate and remedy any issues as and when they arise too.

It is always worth paying extra for these technological safeguards and services as it will simply mean that you are less likely to have to purchase more panels over the lifespan of your system once it has been installed.

Used Solar Panels: Always Check Their Age and Condition

Though purchasing used solar panels can seem like a great way to make short-term cost savings, they might actually put you massively out of pocket in the long term.

Initially, you should have their condition checked over by someone who is well versed in solar technology to determine whether or not they are actually going to be capable of producing their intended power output from the moment they are installed.

Breaks and chips in the panel surface will lead to a loss of power output. The next part of the used solar panel puzzle is to determine how old they are. It is theorized that solar panels can lose roughly 1% of their efficiency every year after their installation according to manufacturer warranties.

Though tests show that the real figure is an average of around 0.4% per year, you should always aim to prepare and calculate for the worst. With this in mind, please observe the following chart that displays how much efficiency a series of different solar panels could lose over the course of their lifespan.