5. How do I know what size solar electric system I need?
Your best starting point is to look at your electric bill and determine your average daily usage in kilowatt hours. Most bills will have this displayed as the total kilowatt hours used over the month. Most homes or facilities use more electricity at different times of the year, so an average over the year will give you your best estimate.
We can then estimate the size system you will need to produce a percentage of your building’s energy. If a system has good southern exposure and no significant shading we know that we will average approximately 4 sun hours per day in our region – accounting for system losses. By multiplying the size of the system in kilowatts times the sun hours per day we can estimate the output of the system on a daily basis over the course of the year.
For example, a 5 kilowatt system will produce approximately 20 kilowatt hours / day (5 kw X 4 sun hours = 20 kilowatt hours per day). If your home uses 40 kilowatt hours a day, the 5 kW system in this example would eliminate 50% of your electric usage.
We recommend energy efficiency practices such as installing compact fluorescent light bulbs and increasing your insulation to decrease your energy usage.