Determine the number of solar panels you’ll need for your house.

Based on an average monthly electricity use of 893 kilowatt-hours (kWh), the average American home requires between 16 and 20 solar panels. After the federal solar tax credit, the cost of installing that many solar panels would be between $12,000 and $17,000.

However, it’s likely that your energy use differs slightly from the national average. In addition, the amount of solar panels you require will also depend on your home’s location and the type of solar panels you select.

So how precisely do you calculate the number of solar panels you require? We have your back.

Factors that determine how many solar panels you need

You could believe that the number of solar panels you require depends on the size of your home, however this is untrue! You must ascertain the following in order to accurately determine the number of solar panels your solar energy system requires:

  • Your energy usage: You need more solar panels to cover your electricity expenditures the more electricity you use.
  • Sunlight in your area: Homes in regions with less sunlight will require more solar panels than those in states with more sunlight to completely eliminate their electricity expenses. Generally speaking, the southwest of the United States receives the most sunlight, while the northeast receives the least.
  • Panel wattage: Most solar panels installed today have a power rating of about 370 watts per panel; fewer panels are required when you install panels with high wattage ratings. The wattage of the solar panels you choose, also known as the power rating, influences how much energy the panels will produce.

Will White, a solar expert, explains all you need to know about calculating the number of solar panels you need to power your home in the sections below.

How to calculate the number of solar panels you need

The quickest, simplest, and most accurate way to determine how many solar panels your home requires is to use our solar panel cost and savings calculator, which you can use without doing any arithmetic. Additionally, we’ll tell you the typical price of a solar installation for your particular house and how much money you’ll save on electricity bills as a result.

To determine how many solar panels you require, simply follow these four simple steps if you want to put pen to paper and do the math on your own.

Step 1: Determine your energy usage 

To find out how much electricity you use each month, look at your most recent power bill. The total electricity usage will often be displayed at the bottom of the bill in kilowatt-hours (kWh).

As energy usage varies seasonally (just think about how much electricity you need for air conditioning in the summer! ), your yearly energy usage will give you the best estimate of how many solar panels you need.

Because the amount of energy used each month changes so considerably, it can be helpful to find your last year’s monthly electric bills, add up the total amount of electricity used, and divide by 12.

However, a rough estimate of your energy consumption can still be made using just one power bill.

Step 2: Find how much energy solar panels produce in your area 

Finding the amount of sunshine your area receives is necessary now that you are aware of how much electricity your home consumes each month. The strength of the sun in your location is generally assessed in terms of something called “peak sun hours,” which is how this is typically expressed.

For each state, we offer a detailed list of the typical daily peak solar hours. This is the daily amount of sunshine that your region receives, but we need to know how much you get each month. Simply multiply the daily peak sun hours in your state by 30 to get this. The U.S. gets between 120 and 150 peak solar hours each month on average.

You may calculate how many kilowatt-hours of power one kilowatt (kW) of solar panels will generate in your area throughout a month using the monthly peak sun hours. Therefore, 1 kW of solar energy will generate 150 kWh of power each month if your state experiences 150 peak sunlight hours each month.

Uncertain of the distinctions between kW and kWh? Read our explanation of the differences between kW and kWh.

Step 3: Calculate solar system size you need 

You can calculate the size of the solar system you need to meet your electricity needs now that you are aware of how much electricity 1 kW of solar will generate in your location.

To get the system size you require in kW, divide your monthly electricity consumption by the monthly peak solar hours in your location. The calculation for the typical American home might resemble this:

893 kWh consumed / 135 monthly peak sun hours = 6.61 kW of solar

Step 4: Figure out how many solar panels you need 

So now you are aware of the size of solar system you require to meet your energy needs. What’s next? Take the solar system size and multiply it by 1,000 to convert it from kilowatts to watts to determine how many solar panels you’ll need. Use the same illustration as before:

6.61 kW of solar x 1,000 = 6,610 watts of solar

Next, divide the power of the solar panels you intend to install by the system’s size in watts. In the United States, solar panels typically have a 370 watt capacity. To satisfy your energy needs, you would therefore require 18 solar panels, for the purposes of our scenario.

6,610 watts of solar / 370-watt solar panel = 18 solar panels

Voila! That’s the number of solar panels you will need to power your home.

How much roof space is needed for solar panels?

Roof space needed for a typical solar installation ranges from 280 to 351 square feet. Simply multiply the number of panels you require by 17.55 square feet, the average area of residential solar panels currently on the market, to get how much roof space your solar system requires.

High-efficiency solar panels, or panels with a higher power output, may be necessary if your roof space is restricted. This way, you can install fewer panels while still meeting your energy needs.

Average number of solar panels needed based on system size

The table below provides an estimate of the quantity of power the solar array will produce as well as the number of solar panels that are required dependent on the size of the system.

System sizeEstimated monthly energy productionNumber of panels*Roof space required
4 kW480 – 600 kWh11193 sq. feet
6 kW720 – 900 kWh17281 sq. feet
8 kW960 – 1,200 kWh22386 sq. feet
10 kW1,200 – 1,500 kWh27474 sq. feet
12 kW1,440 – 1,800 kWh32562 sq. feet
14 kW1,680 – 2,100 kWh38667 sq. feet

*Assumes 370-watt panels

Do solar panels make sense for my home?

The amount of panels you need may also depend on other elements including the direction of your roof, how much shade it receives, the solar inverter you choose, and whether or not you plan to include a solar battery. However, it might be challenging to quantify these characteristics on your own.

Getting quotations from reputable local solar firms is the best approach to figure out the optimum location for your home solar power system and how many solar panels you need. Additionally, solar installers can give you an idea of the up-front costs of installing solar on your house as well as what discounts, incentives, and tax breaks local homeowners are eligible for.

To determine the number of photovoltaic solar panels you’ll need to power your home with clean, renewable energy in the interim, follow the instructions in this article.

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