How many solar panels do I need for my home?

how many panels do I need?

The short answer is it depends on your home. There are many factors at play such as

  1. How much electricity do you consume?
  2. How much of that do you want to switch towards solar?
  3. What is the electricity generation potential of your roof?
  4. How many panels can fit on the roof?

PowerScout has made it really easy to figure this out. Use our online Solar Calculator to estimate if solar is good for your home and if yes, how many solar panels you would need.

Let us take an example to illustrate this:

1. How much electricity do you consume?

The average single family home in the United States consumes about 750 kWh (kilowatt hours) of electricity per month. Of course your household can consume more or less power based on how big your house is, the appliances you have and how energy efficient you are. You can figure out how much your consumption is by looking at your past electricity bills. Taking an average of the last 12 months is advisable as there is variance between summer and winter consumption. Let us say that your household consumes the U.S. Average of 750 kWh.

2. How much do you want to offset with solar?

Typically the answer for most consumers is as close as possible to 100%. However, for some consumers who are paying their current electricity provider Time-of-Use (TOU) Rates, it might be advisable to install a smaller solar system. Smaller systems can be more advantageous for TOU customers because the panels produce electricity during the day when the TOU rate typically has the highest value while consumption is usually weighted towards weekends and evenings when the TOU rates are typically cheaper. So, even with a smaller solar system, it is possible to fully offset a TOU based electric bill. It’s usually not a good idea to oversize the solar power system because most utilities compensate solar system owners for excess generation at wholesale rates which are usually much lower than the retail rates utilities charge. This increases the payback of oversized solar power systems. Let us assume that, in this example, you would like to offset 100% of your consumption with solar power. This means you need enough solar panels to supply 750 kWh of electricity on average per month.

3. What is the electricity generation potential of your roof

1,000 Watts (W) or 1 kilowatt (kW) of solar panels can produce about 125 kWh of electricity per month in sunny regions such as California and Texas. The same 1 kW of solar panels will produce only about 100 kWh of electricity in less sunny regions like New York or Massachusetts. These numbers also vary based on the direction your roof is facing and if there is any shading on the roof.

Let’s assume you live in California and have a clear roof without any obstructions or shading and that 1kW of solar panels can produce 125 kWh of electricity per month. To produce 750 kWh per month, you will need 6kW of solar panels.

4. How many solar panels can fit on your roof

Depending upon the make and model, residential solar panels can be rated anywhere from 250W to 350W. Polycrystalline panels are rated usually lower while monocrystalline panels are rated higher. Let’s assume that your installer is using panels rated at 300W each. To install a 6kW solar power system, you would therefore require 20 panels (= 20 panels x 300W per panel). If the installer uses a higher wattage panel, you would require fewer panels and vice-versa. The last step, is to make sure you can fit the required panels on your roof. In situations where roof space is constrained, it might be advantageous to use higher rated panels even though they cost more.

With PowerScout’s online Solar Calculator, you can get an instant estimate of how many panels you will need for your home and how much you will be able to save from switching to solar power.