asked:


The first thing you might ask – what is solar radiation and how does it related to solar generated electricity? That is a good question and a topic discussed in our next article in our series dedicated to home solar power. This article, on the other hand, explains how kilowatts are calculated based upon the energy output of your solar array. We will also highlight the difference between solar cells connected in parallel versus in series.

The average American home uses about 25 kWh of electricity per day. The following example illustrates how to calculate the power produced by a residential solar energy system. Looking over a solar radiation grid, we can determine that a residence gets five daylight hours of solar radiation in one day which is then averaged out over the entire year.

Solar radiation maps are highlighted on may websites throughout the Internet. You can do a quick search for “solar radiation” to find one. In any area across the entire United States, they detail out the amount of sunshine hitting a given location based upon the time of year and its address.

Calculating the power from a solar energy system

Divide the average kWh per day by the average sun hours per day. For this example, we take 25 kWh divided by 5 hours of sun per day = 5 kW system This 5 kW system will generate 25 kWhs under optimal conditions in direct sunlight for 5 hours, or 25 kWh on an average day with some at peak production and most of the sunlight at less than optimal angles.

Future articles related to solar energy will continue to explain the effects of sun angle, reflection, and refraction on the design, output, and installation of solar panels.

Energy as it Pertains to Solar Modules

Individual solar modules that are measured in watts have a particular voltage (around 40 volts) and a particular amperage (around 5 amps). A solar module with 40 volts and 5 amps is called a 200-watt module, which means that it has the potential to produce 200 watts of electricity when in direct sunlight, away from trees or shading, and clear of snow or debris. Since most electrical components around your house are only rated for 600 volts DC, it is rare to see a solar array with a string larger the 15 solar modules. On the other hand, since inverters need a minimum voltage or pressure to turn them on, you will seldom have a solar array with a string solar modules with a size smaller then 6.