One of the questions we get asked the most is: “How many solar panels do I need to power my home?” This is a case of a simple, straightforward question with no simple answer. That’s because there are so many variables involved. The number of panels you’ll need depends on the amount of power you use, your location, roof orientation and other factors.
How to Calculate Your Solar Panel Needs
If you are interested in calculating for yourself how many solar panels to power your house, here is what we would suggest:
1. Consult your electric bill. The first step is to figure out how much power you actually need. Pulling out a year’s worth of electric bills should give you a pretty accurate answer. Tally the number of kilowatt-hours (kWs) you used in each month, then divide by 12. That will give you your average electricity use per month.
2. Visit NREL’s PV Watts calculator. The National Renewable Energy Laboratory has a handy calculator that simplifies the process of sizing a system. Begin by typing your location into the “Get Started” box. In the following screens, you will be prompted to input additional information about your proposed system. For system size, type in 1 kW. Do the best you can with the rest; clicking the information symbol next to each term will help you determine your answers. If necessary, you can use the default numbers.
3. Get your PV Watts results. Once you’ve entered all your information into the PV Watts calculator, it will tell you how many kilowatts of electricity a 1 kW system will produce per year. This number won’t be exact unless you have specific information about the panels you will be using, but it will be close.
4. Calculate what size system you will need. From there, you can do the math to determine how large a system you will need at your current rate of electricity consumption. For example, if a 1 kW system would produce 1,000 kW of energy per year, and you are currently using 4,000 kW, you will need a 4kW system.
5. Consult solar panel manufacturer’s ratings. Some solar panels are more efficient than others. Once you have estimated your system size, you can use the information provided by the solar panel manufacturers to calculate how many panels of any given brand will be required.
Here Are a Few Other Things to Consider:
• Shading. The NREL website assumes that the panels will be in full sun. If your roof will be shaded at all during any time of the day, it will affect your panels’ efficiency. That is why roof orientation matters, too. Panels on a house facing north will get less sun and produce far less energy than the same ones on a south-facing home.
• Size and structure of your roof. A small roof may limit the number of panels you can install on it. You also want to be sure your roof can handle the weight of solar panels. This is not a problem with most modern roofs, but if you are unsure, it’s best to consult a solar or roofing professional.
• Average need versus total need. Keep in mind that because the amount of available sunlight varies throughout the year, you’re going to overproduce in summer and underproduce in winter. Most people will shoot for producing the average amount each month. This means that some months you’ll be purchasing some of your power from the utility, and other months you may be selling back your excess. It’s possible to oversize your system to run entirely on your own power, but the upfront investment will be a lot larger.
• Your budget. Most households enjoy excellent ROI from their solar systems. However, it is an investment. If your budget is limited, you can elect to install a smaller starter system with fewer panels if necessary.
• Energy efficiency. It is a very good idea to assess your current energy use to see if there are ways you could achieve the same lifestyle with less. You may find that by addressing your energy leaks and/or investing in more efficient appliances, you can get away with a smaller, less expensive solar array with fewer panels.
The Easy Way Out
At this point, you may think that calculating solar panels for your house sounds like a lot of work! And you’d be right.
However, there’s a way you can get your answer without lifting a finger. Well, almost. Just
click here and request a free solar estimate. Or call us at [company_phone]. As one of the largest solar installers in the Mid-Atlantic region, we’ve helped hundreds of home and business owners in Maryland, DC and surrounding states go solar since 2002. We’d be delighted to help you, too!