Calculate energy consumption for my solar system

Okay, so with solar systems the most important thing is knowing your actual consumption. Look at your last electricity bills - they'll show you in kWh how much you use on average per month. In my warehouse for example we have about 15,000 to 20,000 kWh per year, but that's obviously completely different than a private household. For you what matters is: multiply your monthly kWh by 12, and then you've got your annual consumption. That's your baseline number.

Now you need to know how much sun you actually get. That depends heavily on where you live, how your roof is oriented (south is optimal, but east/west works too) and how much shade you have. The tilt angle should ideally be between 30 and 35 degrees. You can check out sites like photovoltaic calculators or ask an installer - they usually have better data for your region. With this info you can then calculate how many kWh your system will roughly produce per year.

Then it's relatively straightforward: if you need 5,000 kWh per year and a 5-kWp system gives you maybe 4,500 to 5,500 kWh per year (depending on region and conditions), then that works. But keep in mind that you produce less in winter than in summer, so you might need a battery or a plan for the dark season. Some people size their system bigger to have enough even in winter - so a 20 to 30 percent buffer isn't a bad idea if you want to be independent.

I wouldn't just grab some random average values you find online - they rarely match your actual situation. At my workshop, we planned a system last year and before that I spent three months reading the meter every single day instead of just looking at the yearly bill. That showed me my consumption is almost three times higher in winter than in summer, and if I hadn't done that it would've totally skewed the planning. Write down over a month or two when you use the most power - mornings before work, evenings cooking, at night? Then you've got a solid foundation to work with.

After 20 years in security, I know my way around consumption meters pretty well 😄 but I'd add one more thing: don't just look at your annual bill, but also how your consumption is spread across the months - in winter you usually need more electricity than in summer, and that's important for planning your system. At home I do a lot of knitting in the evenings, so I have another light running too, stuff like that you should factor in. My colleagues here are right about the kWh, but don't forget: your actual solar system should be oriented to your average daily consumption, not just the annual balance 👍