Going off-grid means completely disconnecting your home from the national power grid. You have to find an alternative way to power your appliances, and the easiest solution is solar energy. However, going off-grid requires more than simply installing a couple of solar panels and connecting them to a battery.
If you have contemplated going off-grid, the first question you probably asked yourself was, how many solar panels do you need? The answer to this varies and will depend on several factors.
How many solar panels do you need?
The exact number of panels you need will depend on the following factors:
Your energy needs
The first step to determining the number of solar panels you require is first figuring out how much power you need. You need to generate enough power to power all your appliances now and in the future. You can look at your utility bills to see how much energy you consume and use that as a starting point.
Alternatively, you can calculate how much power you use by looking at the power rating for your devices and adding it up. For instance, if you need to power your off-the-grid solar generator, check the power rating label to determine how much power you need. You also need to factor in how long you will use the device daily.
It’s best to think of the worst-case scenario, this way; you have enough power at all times. For instance, if you only turn on your lights for 2 hours during summer but they stay on for 7 hours during winter, work with 7 hours. By multiplying the device’s wattage by the amount of time it will be on, you will get how much power it needs. Do this for every device, then add it up.
The amount of direct sunlight you get (irradiance)
Once you know how much power you need, the next step is finding out how much sunshine your area gets. Ideally, you want to use the month you get the least sunlight, so you always have enough power.
These peak sunlight hours are not equivalent to the time between sunrise and sunset. They refer to when the sun reaches an average of 1000 Watts per square meter. Basically, when the sun is most powerful, allowing the panels to be most productive. You can check the National Renewable Energy Laboratory website to see how many hours of irradiance your area gets.
The amount of available space
Lastly, think about how much rooftop space you have. You need to place the panels where they will get the most exposure to direct sunlight for most of the day. The amount of space on your roof also dictates how many panels can be installed.
The type of solar panel you pick
Once you know how much power you need and how many hours of irradiance and space you have, you can calculate what size panel you need and, in turn, how many panels you require. Start by calculating how many hours of irradiance you get a month.
Say you live in portland and you get an average of 4.2 hours of peak sunlight, multiply that by 30 to get the monthly average.
4.2 x 30 = 126 hours of irradiance.
Next, divide your monthly electricity use by those hours
So if your electricity use is about 1000kWh, divide it by 126hrs equals about 7.9. This means you need about 7.9kW to power your home.
Now convert the kilowatts to wats to figure out how many panels you need. Simply multiply 7.9kW by 1000
So 7.9 x 1000 = 7900 Watts.
If you pick a 300-Watt panel, you would need about 27 panels to power your home.
Going off-grid is an attractive option to anyone who is environmentally conscious and looking to reduce their ecological footprint while saving some cash. That said, before you go off-grid, it’s important to determine how much power you require to generate, as this will determine how many solar panels you will need for your system.
