System sizing is an important part of planning your solar installation. So, how big does the system need to be? It depends on what you want to run. In this article, we will take a look at what a 3kW, 8kW and 20kW system could do for you.
A 3kW solar power system will generate about 375 kWh per month or about 12.5kWh per day. So what can you do with 12.5 kWh? The simplest example is that you could run five 100 Watt light bulbs for the whole 24 hours, but, that’s not very practical. You could blow dry your hair for 7 hours but that will give you split ends.
Being realistic, a 3kW solar system could run a 55 gallon electric hot water heater for a day (with average household use). If it is not too hot outside, it could keep one room cool all day with a 9,000 BTU window air conditioner. If you have an average electric car, 3kW of solar would generate enough energy for you do drive about 40 miles. But, keep in mind it could only do one of these things, if you want to do all of them, you are going to need more than 3kW.
So let’s go bigger and see what an 8kW solar system can do. It would have an average output of 33 kWh per day which would be enough to do three loads of laundry with a standard washing machine and electric clothes dryer, one load of dishes in the dishwasher and keep the hot water heater going through it all. If laundry and dishes doesn’t sound like fun an 8kW solar power system would generate enough to drive your electric car 75 miles then come home and cook a turkey in your electric oven. But, if it’s hot outside and your house is 4,000 square feet, the entire output of that 8kW system would be needed to run your central air conditioning.
What about 20 kW of solar? With an average output of 83 kWh per day, it can power quite a lot. More than the average household would need. You could keep the hot water heater running while you do two loads of laundry and a load of dishes, then drive 40 miles in your electric car, cook the turkey and run the dishwasher again all while your 4,000 square foot house is being air-conditioned and your kids are watching TV with all the lights on. But that might wear you out which is why the average residential solar power system is not quite this big.
The purpose of this article is to give you a general idea of what solar can do. The best way to size a system is to look at your electric bills from the last 12 months and put in enough solar to generate as many kWh hours as you have been using. If you are looking at solar for an off grid application, then you will have to be very specific about each appliance you are going to use and for how many hours as well as account for the fact that solar generates less energy in the winter and more energy in the summer.