Mike Militello from Greenway Solar discusses sizing a PV solar system….
Sizing Your PV Solar System
Sizing Your PV Solar System is much easier for grid-tied system vs an off-grid system. Your utility company has provided most of the records for you in the form of your monthly utility bills.
Your load capacity will depend upon your overall energy needs. Utility company’s charge based upon how many kilowatt hours you use per month. Furthermore, every electrical unit has a reading measured in watts, volts or amps.
To start sizing your PV solar system, first find out how many kWh you use on average per month and create a system based upon your overall electric bill. Once you have completed this task, you may be surprised at how large a system this would actually create. You may also find that you just don’t have the roof or ground space to support a system to cover all your power needs.
The Golden Rule of Solar Power: It is More Cost Efficient to Conserve Energy then to Produce Energy.
There are many ways to cut down on your electric use, or change out appliances within the home (check out the videos on Energy Conservation in the Home). If your utility has a tiered billing structure where you are billed a rate for baseline usage, and then higher rates for a percentage of power used above that baseline, you may be able to build a solar system that eliminates the overages and higher rates which equates to a greater savings per the investment.
The following steps will help in determining sizing your PV solar system.
- Find your monthly average electrical usage from your electricity bill. This will be listed in kWh (kilowatt hours)
- Find your daily average electric use. This will be your monthly average kWh divided by 30
- Find your locations average peak sun hours per day. The map to the right has rough estimates
- Calculate the system size (AC kW) to cover 100% of your electric bill. Divide your daily average electric use in #2 by the figure in #3
- Divide your result in #4 by .77 to get a loss factor for the components in the system. This takes into account the temperature loss, wire loss and component inefficiencies, etc.
- Multiply your result in #5 by 1000 to get watts of system. Divide the wattage of the module that you would like to use into this number to determine the number of modules you would need.
To Calculate Sizing Your PV Solar System, Use this Handy Calculator.