Solar energy system sizes are measured in the amount kilowatt hours (kWh) they can produce. 1kW is equal to 1000 watts. As you may suspect, higher kWh systems are able to produce more power per hour, but also require more hardware (panels, inverters, racking) to achieve this higher production. To determine the solar system size that is able to offset your total energy consumption follow these 5 simple steps:
1. Look back at your energy bills over the past 12 months (each statement should tell you your monthly kW usage).
2. Take that annual total and divide by 12 to get your average monthly usage.
3. Divide that number that 30.5 to get your average daily usage.
4. Divide that number by the average daily sunlight hours for your region. This would be your proposed system size at 100% efficiency.
5. To account for variables, derate factor for an 85% efficient system. This is your final proposed system size.
Keep in mind that offsetting your average energy consumption is not the only option you have when it comes to installing solar. In fact, simply offsetting your energy usage may not be what’s financially best for you in the long-run. Depending on your goals for installing solar, it may be more beneficial for you to install a system that is somewhat smaller or larger than your average usage. A smaller system can help offset just a portion of your electricity bill, and you can get the rest of what you need from your utility company. This is a great option for folks who don’t have the funds for a system that exactly matches their usage and it still results in more fixed, predictable, and lower monthly energy costs. A system that’s larger than your monthly usage may make sense if you live in a region with renewable energy credits, which allow you to earn money for the excess energy you produce.