As with all Do It Yourself projects, there are always Questions of how to do things. This will be the page for finding the Answers to Frequently Asked Questions and for other supporting documentation.

## Solar Q&A: How Many Solar Panels Do I Need?

Of all the things you have to figure out when planning a solar power system, the number of panels you’ll need is a big one. Yet, all variables are interrelated and you can’t figure out how many panels you need unless you know some other important information first.

What is my daily power consumption?

You need to calculate how much power, in watts, you use on a daily basis. Your electric bill will be necessary for this. A lot of utilities actually break this down for you in your monthly statements. If you’re not so lucky, there areonline tools to help you out.

How much sunlight do I get per day?

Another thing you’ll need to know is the average amount of peak sunlight you get per day. This means yearly average. So don’t think summer hours; many areas get great sun in the summer but you might not see it for what feels like a month in the winter. Be sure to calculate the average…and be conservative. There are online calculators to help you get this exact also.

How many panels do I need?

Once you know your average power consumption and the amount of sunlight you receive each day, you are ready to calculate the number of panels you’ll need. It is easy. First divide the total watts you use each day by the hours of sun you receive. That is the number of watts you need to generate in one hour. Solar panels are rated in watts. For instance, a 200-watt solar panel will produce 200 watts of power each hour of peak sunlight. Therefore, if you need to produce 500 watts of power each hour then you’ll need five 100W solar panels. Note that panel ratings vary, meaning you could choose five 100W panels, ten 50W panels, or just one 500W panel. You get the picture…

Also keep in mind that while some people do get all their power from solar panels, most use solar panels to supply a percentage of their electrical needs. You can always start small and add on later. Think about your energy goals, the amount of money you hope to save each month, and how much you can afford to pay for a system up-front.

10 Free, Online Solar Calculators

Did you know that the answers to many of the most common questions about solar power are available at the tip of your fingers … literally? Check out this list of solar calculators that are simple to use and available online. Each calculator is different, helping you determine such things as the tilt your panels should be, the system size you should purchase given how much energy you want to save, the amount of usable sunlight you can expect in your area, and other helpful information. The calculators can potentially help you determine which panels to buy, before you purchase; or, help you understand your system better, afterwards. Keep in mind though, that the calculators aren’t error-proof!

- PV Watts Calculator. After typing in your location, system information, and cost of electricity, this calculator will help you track your panels’ energy production and its dollar value.
- Solar Trading Post Calculator . This calculator will help you determine what kind of system you need. Simply enter your location, average electricity bill, and desired return, and the calculator will recommend a system size as well as automatically generate the cost of the panels in your area. It even pulls up rebate information in your area.
- National Renewable Energy Laboratory (NREL) Calculator . This calculator will help you determine the sun’s position and intensity, given different locations and times.
- Square One Research Calculator . This interactive calculator also helps you determine the position of the sun, given a latitude, longitude, and time.
- Where-RV-Now Calculator . For all you RV owners, this calculator will help you discover your solar panels’ power output, given the specs of your system.
- Rainbow Power Company . This Amp & Watt Hour Calculator is provided to help you understand some basic electrical terms & calculations. It can give you an estimate of your total power usage (in either amp hours or watt hours).
- Solardat Calculator . Fill in your latitude, longitude, and time zone, and this calculator creates a PDF chart of the path of the sun for the specified time. It could be used to evaluate hours of usable sunlight. (hint, hint, see #6)
- Solar Calculator . Solar Calculator helps homeowners and businesses research solar system prices. Learn how much solar PV costs and discover different types of solar systems.
- Midsummer Energy Calculator . This calculator will help you calculate approximately how much energy you use every day.
- Free Sun Power . A great site for basic knowledge of PV and off grid calculators.