Calculate how many solar panels you need for your home

Calculate how many solar panels you need for your home
Reading Time: 4 mins

When you want to install a solar system for your home, how do you calculate how many solar panels you need for you home? Let’s learn all about it!

Factors that determine how many solar panels you need

You may think that the size of your house determines how many solar panels you need, but it doesn’t! To really understand how many solar panels your solar energy system needs, you need to determine the following:

  • Your energy usage: The more electricity you use, the more solar panels you need to cover your electricity costs
  • Sunlight in your area: Homes in areas that receive less sunlight will need more solar panels to eliminate their electricity bills than those in sunnier states. As a rule of thumb, the southwestern United States gets the most sun in the country, while the northeast gets the least
  • Panel Wattage: The wattage of the solar panels you choose, also called the power rating, determines how much energy the panels will produce and most solar panels installed today have a power rating of about 320 watts per panel; fewer panels are needed when you install panels with high wattage ratings

How to calculate the number of solar panels you need

Our solar panel cost and savings calculator is the quickest, simplest, and most accurate way to determine how many solar panels your home requires – and it doesn’t require any arithmetic. We’ll also tell you how much a solar installation will cost on average for your home and how much money it will save you on your electric bills.

If you prefer to put pen to paper and do the math yourself, follow these four simple steps to figure out how many solar panels you’ll need.

Step 1: Determine your energy usage

To find out how much electricity you use each month, look at your most recent power bill. In most circumstances, the total quantity of electricity used in kilowatt-hours will be shown at the bottom of the bill (kWh).

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

As the monthly consumption varies so much, digging your electricity bills monthly over the last year, adding electricity usage together and dividing them by 12 can be advantageous.

But it is still sufficient to estimate a ballpark using only one bill to locate your energy consumption.

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

Now that you know how much electricity your home uses in a month, you need to find the amount of sunlight your area receives. This is usually measured in something called ‘peak sun hours’, which is essentially the intensity of sunlight in your area. 

This number is how much sunlight you receive daily, but we need to know how much you receive monthly. To do this, simply multiply your state’s daily peak sun hours by 30. 

The monthly peak sun hours you get tells you how many kWh of electricity 1 kilowatt (kW) of solar panels will produce in your area in one day. So, if your state receives 150 monthly peak sunlight hours, 1 kW of solar will produce 150 kWh of electricity per month.

Step 3: Calculate solar system size you need

You can now determine what size solar system you need to satisfy your electricity needs now that you know how much 1 kW of solar will produce in your area. Divide your monthly electricity consumption by the monthly peak sun hours in your area to determine the kW system size you require.

Step 4: Calculate how many solar panels you need

So you know how big of a solar system you’ll need to cover your energy needs. So, what now? To determine how many solar panels you will require, multiply the solar system size by 1,000 to convert the size from kilowatts to watts.
Next, divide the system’s power by the wattage of the solar panels you intend to install.
Voila! This is how you calculate how many solar panels you need for your home!

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