Archive for the ‘energy efficient’ Category

How Many Solar Panels Do I Need For An Electric Solar Power System in Tacoma?

Wednesday, February 1st, 2012

Aside from determining cost, knowing how many solar panels you need to potentially power your home in Tacoma helps you picture what the finished product will look like. After all, you want your home to be energy efficient, but you also want it to not be an eye sore. Estimating how many panels you will need involves some research and math, but it can be done simply enough and is worthwhile. Below are some steps to help you estimate how big your array will need to be:

Researching Solar Panels

First up, decide how much of your energy needs you want a solar array to provide. For example, you may choose to keep your home on the utility grid, but plan to have 50% of your home’s energy come from solar. The steps below assume 100% solar energy.

You should also determine your current energy usage. You can do this by looking at old utility bills. It is best to look at usage over a span of 6-12 months in order to get an accurate estimate. You will usually find this figure in kilowatt hours (kWh). Estimated energy use for an average American household is about 740 kWh per month.

Another important step is to find the insolation value for your area. This number reflects the number of hours in a day that a solar panel will perform as rated. You can find reference tables of insolation values online.

Calculations for Your Solar Panels

Now comes the fun part – a little bit of math. First, you need to figure out the desired wattage output of your system. To do this, divide the number of kWh to be produced in one day and divide it by the insolation value. Using the average monthly usage from your research, you can see the daily average usage is about 24 kWh per day. With an insolation value of 4 hours (for example), a solar array needs to generate 6 kilowatts per hour. Because the system is not 100% efficient, raise that value by 30% to account for possible energy loss. This system will need to generate 7.8 kilowatts per hour. Since large solar panels produce about 130 watts per hour each, this system would require about 60 panels.

Note that this is an extreme example, as most homes won’t use solar for 100% of their energy needs. You will almost certainly use fewer panels; these steps are just meant to help walk you through the process. There are also calculators available online to make the estimation process a little simpler.