Nov 18, 2020

How Many Solar Panels Do I Need?

As more homes throughout the country consider installing solar panels, one question commonly asked is, “how many solar panels do I need?”. Well, it depends – there are a few factors that go into determining how many solar panels you would need to power your home or business; home energy usage, roof or property surface area, orientation of your roof and geographic location. In this piece, we’ll break it down for you.

How much solar energy do I need?

When determining how much solar energy you need; your home’s average energy usage is the first thing to look at. According to the U.S. Energy Information Administration, in 2019, the average electricity consumption for a U.S. residential utility customer was 10,649 kWh. That’s an average of about 877 kWh per month. To understand your own usage, a good rule of thumb is to look back at your total energy consumption from the last twelve months on your utility bills. Most utility bills provide this information. Divide that number by 12 and you have a great estimate of what you’ll need your solar panels to generate each month.

Where you live also plays an important role in how many solar panels you’ll need. For example, states in the northeast endure longer winters accompanied by shorter days during cooler months. Residents in these regions will most likely need more solar panels to generate the same amount of power as residents from sunnier and warmer climates would. It’s important to understand how many peak hours of sunlight your geographic location receives on average.

How much solar powers a home?

When estimating how many solar panels your home could need, it’s important to consider the size of your home. An average homeowner would need about 28 to 34 solar panels to fully offset their electricity usage. The chart below is an estimate of the number of panels you could potentially need based on the size of your home.

*Data from the Residential Energy Consumption Survey.

How to calculate how many solar panels you need Now that we’ve laid down the groundwork, it’s time to crunch a few numbers to help you calculate how many solar panels you’ll need:

  1. Calculating your monthly average kWh – The first step is finding your monthly kWh usage. As stated above, add up the amount of kWh usage of your home for the past twelve months and then divide that number by 12. Let’s use the national average monthly residential electricity usage above as an example, 877 kWh.
  2. Peak hours of sunlight – A peek sun hour is an hour of sunlight that offers 1,000 watts of photovoltaic power per square meter, usually when the sun is at its highest point in the sky. Let’s use our location. In Massachusetts, the average peak sunlight hours are 4.
  3. Crunching the numbers – Input both of the figures above (average kWh usage and peak sunlight hours) into the formula below: average monthly kWh usage / (peak sunlight hours x 30 days). So, using the numbers above: 877 / (4 x 30) = 7.3 kW solar system.
  4. Total watts – Next, you’ll need to convert your kW by the wattage output of one solar panel, and since 1 kW equals 1,000 watts, we’ll need to multiply 7.3 by 1,000. 7.3 x 1000 = 7,300 watts
  5. Divide your total watts by the average output of one solar panel – Let’s use the number of watts one standard 250-watt panel generates to calculate how many solar panels you would need. 7,300 / 250 = 29.2 solar panels

So, if you use 877 kWh per month in the state of Massachusetts, you will most likely need a 7.3 kW solar system (29.2 solar panels) to offset 100% of your utility bill.

Not all roofs are suitable for solar panels

According to the National Renewable Energy Laboratory of the U.S. Department of Energy, approximately 50% of homes can’t support rooftop solar panels. Community solar programs are a common way for many homeowners, businesses and renters to go solar without actually installing anything on their roof. Participants can subscribe to a nearby solar farm and pay a lower price for the electricity sourced from it. Through Community Solar with Nexamp, the process is similar to determine the size of a subscribers’ share of a solar farm is similar to determining the number of rooftop solar panels. We simply analyze a subscriber’s last 12-13 months of energy usage and recommend a suitable allocation of our farm for them to subscribe to at a discounted rate. The end goal is to offset as much of a subscriber’s annual electricity costs as possible.

At the end of the day, the number of solar panels you’ll need to see potential savings is unique to your home’s energy usage. Interesting in seeing how much you could save by joining our community solar program? Reach out to us by visiting our community solar page or call us at (800)-945-5124.

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