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Solar Sizing

Once you know solar is right for you, how much do you really need?

Deciding how much solar you need to install is called "sizing" and your solar installer will help you with this. The number of solar panels an installer will recommend for your property depends on several factors including your geographic area, the amount of sunshine the panels will get, the type of equipment installed and how much you spend on electricity.

Determining how many solar panels you need is an important part of your solar research. The solar contractor you select should size and design your system for free without any obligation to buy. It all starts with looking at your monthly energy bills. These will give you an idea of how much electricity you use in a year. The average home consumes 10,400 kilowatt hours (kWh) of electricity each year.

Solar systems are rated by their power output in kilowatts (kW). As a rule of thumb, each kilowatt of solar array takes about 100 square feet and produces about 1,100 kWh per year.  Systems rated between 5 and 10 kW are generally sufficient to meet the power needs of most homes.

If your system is sized to produce more power than you can use, you may end up with energy credits on your bill that you can’t use. Some states allow you to give your excess energy credits to other electricity customers, but ideally, your solar installer will size your system to meet your own estimated household usage.

Because solar systems produce energy only during daylight hours, you’ll have to draw electricity from the grid to power your home when the sun is not shining. That means you’ll still have a monthly utility bill even with the credits you receive for excess electricity produced during peak solar hours.