An energy assessment is simply an evaluation of how much energy you use today and a calculation of how much solar power generation is required to meet the needs of your household or business. You can figure this out for yourself by answering three basic questions.
Start with your monthly electric utility bill. Find the kilowatt hours or kWh used. Most utility bills will show the current month, the last 12 months and the average daily kilowatt hours used in the home or business. For the upcoming calculation, you want to know the annual kWh used for the most recent 12 months. Make a note of this. It is also good to look at the monthly variance to understand your high and low consumption throughout the year.
For most utility grid-connected homes, the amount of solar energy needed is between 50% to 100% of the annual kWh used. The difference really depends on the available space and your budget. More on these later.
For grid-tied systems, the solar panels will typically generate more power than is needed in the home during the daytime. Don't worry, your electric meter will spin backwards as the extra power is sent to the utility company. Known as NET-METERING, the utility will give you credit for the extra power. Then at night, when the solar panels are not working, the power comes from the utility, going against the credits built up during the day.
For off-grid systems, a more detailed calculation is needed to determine the energy load in AC kWh that will need to be supplied. This requires information about every device that demands energy - how much power it draws, how long and how frequently it is turned on. Contact Us Here for help with an off-grid load estimate.
How Many Watts of Solar Power Do I Need?
We will use the calculator below to estimate how many kilowatts (kW) of solar power are needed to generate your energy. First, enter the yearly kWh from the electric bill or off-grid load estimate. Then enter the daily Sun Hours for your location. Scroll down to see the color-coded map to find your location. Next, enter the % of your electricity bill to offset with solar panels. Click "Calculate" to see your DC watt size.
Once you know the amount of watts, then the number of solar panels can be determined. For example, if you need 1,000 watts or 1 kW of power, and you select 250 watt PV modules, then you would need four (4) solar panels.
Remember, you decide how much solar to get based on the need, available space and budget. There is no rule that you have to offset 100% of current energy use. Sometimes it makes better dollars and sense to start small and add-on later as prices are expected to decline. If you are a high volume utility user, you may be paying a higher rate for the larger consumption. Installing a smaller system to offset just 25% of your energy use may reduce the monthly power bill by 50%.
Find your Solar Hours per Day using the color-coding on this map. Enter the value for your location into the solar calculator.
The solar map uses insolation, a measure of solar radiation energy received on a given surface area in a given time. This is typically measured in kilo-watt hours per square meter per day (kWh/m2/day). The map shows the average daily total solar radiation throughout the United States. The U.S. Department of Energy, National Renewable Energy Laboratory (NREL) developed it.
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