What size solar power system do I need?

Solar Panels for sale here!What size solar power system do I need for my home? This is one of the most common questions that comes up when home owners begin doing the initial research into making an investment in a grid-tie solar power system. And the answer is usually this: it depends on how much of your own power you want to produce or on how much you want to offset your monthly utility bill, depending on your reasons for choosing to install your residential solar power system. And it’s actually very easy to calculate. Just follow the the instructions below and you’ll be able to get a very good idea of what size solar power system you need. So, let’s begin.

The first thing you should do is to get a piece of paper and a pen or pencil.

Next, gather together all of your electric bills for the past 12 months and spread them before you so that you can see each one. Locate the section of the bill that gives the number of kilowatt-hours used. Write down on the piece of paper the name of the first month and the kWh used during that month. Do this for all twelve months, up to the current month.

Now, add up the kWh for those 12 months to calculate the number of kilowatt-hours you used during that 12-month period. Once you have the total, devide it by 12. This will give you the avarage monthly kWh usage for your home.

Next, take that number and divide it by 30. This will give you your average daily kWh usage. Now, look at the solar insolation map below and select the number that most closely matches the color in the area in which you live. For example, the extreme desert southwest of the United States is a maximum of 6.5 and the northern tier of states are a 2.5. Florida is a 4.5. Nevada is a 4 in the north and a 6 in the south.

Once you have your solar insolation, or “sun hours”, number, divide your average daily kWh by the sun hours number. The resulting figure from this calculation will be the size of a solar power system capable of producing 100% of your energy needs. If you want to produce only 50% of your needs, then simply divide the result by 2. So, here is what it looks like for an example that has a monthly usage of 860 kWh:

860 (average monthly kWh) ÷ 30 = 28.66 (Average Daily kWh Usage)


28.66kWh ÷ 5 (sun hours) = 5.73

Thus…5.73 kW is the size of a solar power system that will provide most of your electricity needs.

We can get you most of the way there with our 5.52kW Online Solar Grid Tie System kit which includes everything (mounting hardware sold separately) you need to get you going producing your own electricity.

Perhaps you only want to produce half of the electrical power you use. In that case, just divide your calculation by 2 and that will be the size solar energy system you need to produce 50% of your electricity needs. You’ll want to keep in mind that your usage will vary depending on the season. So you’ll use more electricity in the winter and summer months than you will in the spring and fall. But over the course of the year your usage of (and your bill) should average out to +/-0.

We carry a complete line of pre-packaged grid-tied solar power system kits in various sizes which you may find suitable for your needs. If you require a system for which we have no listing, not a problem. Just e-mail us, call us at 877-226-5073, or use our convenient contact form and we’ll do everything we can to help you design and assemble the right system for your needs.

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Thank you visiting MrSolar.com and we hope you’ll come back to us for all of your solar power product and component needs. Because at MrSolar.com, “We know solar panels!”

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