subject: Determining the Correct Number of Solar Panels [print this page] The number of solar cells necessary per house is dependent upon many factors such as electrical power demands, your weather, the angle of your roof, nearby shade issues, and the size of the cells.
First, it is important to determine energy usage. This changes from day to day, but an average can be found. It is best to overestimate as conditions are likely to change. A common way to calculate need is to find your daily usage then to multiply it by .25. This will help you find the number and size of panels you need in kilowatt-hours. The electric meter on your house should have an odometer style readout or a dial type readout. It is a good idea to record the usage over several days so you can obtain an average. Past electric bills will also help you find your average electricity use from previous years.
Research shows that the average home will use 25 kWh per day, however this does vary. Another common option is to take the highest usage you have ever had in a day and add 10% to find the amount of energy you will need.
Available sunlight is another variable that is necessary to consider. The factors involved in this are the average of sunny days, shade issues, and your roof's angle. Flat roofs take some extra effort to set up.
The amount of sun required to produce electricity varies from location to location. This is due to the difference in sun across the surface of the earth. It is easiest to collect sunlight if your house faces south in the northern hemisphere or north in the southern hemisphere. Sometimes, it is not that simple and extra calculations must be made. Included is the length of sunlight during the day, the angle at which the sun is shining, and the time of year. This information can all be found locally, as well as how much sun is needed in your area to produce a kilowatt of electricity.
Another thing to take into consideration is how much stored energy you are using versus how much you are receiving. It is always wise to store some energy for a rainy day. It is possible to either store electricity in deep cycle batteries, or if you are on-grid you can feed the electricity back into the utility grid. This can end up with the utility company owing you money instead of the other way around.
After considering all of these variables you will be able to find the right solar panel for you. Each panel varies in output as well as varying watts and amps. Panels come in a variety of prices, but the least expensive is not always best. It is important to consider the investment you are putting into them and the durability and efficiency they may have.
Individual solar panels will be labeled to tell you how many watts they produce. Depending on the amount of watts, it is necessary to divide your kilowatt-hour usage per day by the average number of daylight hours for your area. You then take the answer and divide it by the number of watts on your panels to get the number of panels you need. If you build your own panels it takes about 80 cells to make a 100-watt panel.
