How Many Solar Panels Do I Need?

Now that you’ve started planning your DIY home solar power system, you may be wondering how many solar panels you will need to power your house.

In order to find out how many solar panels you’ll need, we need to answer a couple of questions first:

  1. How much electricity do you use now?
  2. How much can you save through conservation?
  3. How much of your own electricity do you want to generate?

Once you answer these three questions, it will be simple enough to calculate the number of solar panels needed to provide the power you need.

How much electricity are you using now? This basically boils down to one number: how many kilowatt-hours you use each month. This can be found on your monthly electric bill. This number, also known as KwH, is the unit that your power company uses to calculate how much you pay each month. The unit of one kilowatt hour represents a 1,000 watt electrical load that consumes power for one hour.

How much electricity can you save? Have you replaced your inefficient old incandescent bulbs with new Compact Flourescent Light bulbs? (“CFL’s”) How about your appliances, are they EnergyStar certified? Before you start your home solar power setup, you’ll want to reduce your electric usage as much as possible through conservation.

How much of your electric usage do you want to replace with electric power from your DIY solar panels? Most homeowners starting out with home solar power begin with the goal of producing 40% of their own energy with solar. As time goes on you can grow and expand your system by installing more solar panels. This will help you move toward your goal of generating 50%, 75% or even 100% of the electricity that you use every month.

So let’s use a concrete example. Let’s say you currently use 800 KwH per month. Then by replacing light bulbs, turning off electronic items when they are not in use, etc., you reduce your monthly usage to 600 KwH per month.

Then you decide that you will want to replace 50% of your usage with your own solar power. That would come out to 600KwH * 0.50 = 300 KwH per month.

Let’s assume that your location gets an average of 6 hours of sun per day. This takes into account some rainy and cloudy days. That’s 6 hours per day for 30 days = 180 sun-hours per month. In order to generate 300 KwH of solar electricity per month, we’ll need to have 1.667 Kilowatts of solar panel generation. That’s 1667 watts of generation capacity. If you have panels that generate 80 watts each, that will take about 21 panels running at 80 watts.

This may sound like a lot at first, but remember that you can start with even just one panel and get moving towards your goal of energy independence. You can easily add more panels as your time and budget allow.
Also, remember that there are now federal tax credits available that will refund you 30% of the cost of any solar panels, solar power inverters, charge controllers, and related solar power equipment that you may purchase.

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