Welcome to our

All Thing Solar Blog

Solar System Sizing

By James Kennedy, Founder and President Beach Cities Solar Consulting LLC

Are you a California homeowner that wants to go solar but is not sure how to go about sizing your solar system?  How do you know how much energy your home is using?  

The first step in the process is determining how much energy your home uses.  You can do this by looking at a recent electric utility bill and seeing how many kilowatt hours (kwh) you consumed in that month.  If your energy consumption is the same for all twelve months you can simply multiply your monthly kwh usage by 12 and that will give you your annual kwh consumption.  However, most California homes use more energy in the Summer and early Fall months from air conditioning to cool their homes so you may have to go through the electric bill for every month and add up the usage to get your annual energy consumption.  If you have not yet installed air conditioning you can take your annual energy consumption and multiply it by 1.2 to determine what your new electrical “load” will be.  The same goes for the purchase of an electric vehicle.  If you have not yet purchased an electric vehicle but are going to do so you can add 2,400 to 3,600 kwh (per electric vehicle) to your current annual energy consumption (depending on how much you will be driving) to determine your electrical load (if you have questions on this, please reach out here).  Finally, if you are going to be installing a pool in your home you will need to take the annual energy consumption and multiply by 1.2 to determine your future electrical load.  


An SDGE bill from a San Diego home solar project I consulted on.  This homeowner used 795 kwh this month.  Their usage history is in the lower right corner graph and you would add up all twelve months to get the annual electrical load in kwh.   


Once we have your annual electrical load figure, we can build a home solar system to produce enough solar energy to offset almost all your electrical bill (this will be determined by how much roof space or vacant land you have available to install the solar panels on).  Most California homes use around 12,000 kwh per year, but this figure is going up with so many California homeowners purchasing electric vehicles and installing air conditioning!  

Let us use this figure as an example to determine how many solar panels your home would need.  Let us assume this is a home in Manhattan Beach and has an East/West facing roof (the location of the home and roof play an important part in how much production the solar arrays will get).  This Manhattan Beach homeowner would need to install 28 solar panels (using 320-watt solar panels) or an 8.96 KW solar system that would produce 12,387 kwh/year to fully offset their electric utility bill.  Of course, we would need to ensure that the home is able to fit all 28 solar panels on the roof with proper setbacks to ensure compliance with fire code.  

Sizing your solar system is a free service we offer to all clients.  Get started by e-mailing us your most recent electric bill, a picture of your electrical panel (we need to see all the circuit breakers), and a picture of your roof today: info@beachcitiessolarconsulting.com