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ST Stefan_2005 DE 🔍 Enthusiast 💬 27 answers ⚑

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.

FI fischer72 DE 🌱 Newbie 💬 1 answer ⚑

You definitely need your last electricity bills to see how much kWh you actually consume per year. At our place, it was always around 3500-4000 kWh per year at first, until we realized the old fridge was an absolute power hog - after that it was just under 3000 kWh. That's the thing: most people just take some random averages, but your household isn't average. Look at the estimated charges on your bills - those are usually already calculated based on your actual consumption, not on some formula.

If you want to get more detailed about it, write down your meter readings regularly over one or two months - best in the morning and evening - then you'll also see when you use the most. Is it the winter months because you're heating more (well, electricity for an electric heat pump for example), or do you consume more in summer because of air conditioning or whatever? That's crucial, because your solar system produces the most in summer, but that's exactly when your consumption might be low. Then it wouldn't be as beneficial for self-consumption as a system with a battery or grid feed-in would be.

The payback period also depends on the quote price - based on the costs I've seen over the last two years, systems run about 1500-2500 euros per kW installed, which for smaller roofs means it takes 5-10 years to break even. Still usually worth it though, if your roof is suitable.

petra_wind DE 🔍 Enthusiast 💬 41 answers ⚑

The bill alone isn't quite enough, though, because your consumption swings wildly depending on the season - winter is way higher for most people than summer, and that's exactly when the sun shines shortest 😅 That's the thing: your system needs to match your actual consumption peaks, not just the average.

Best thing is to write down for a week or two when you need the most electricity (mornings for breakfast, evenings while cooking?), then you'll see if the solar output actually fits your rhythm or if you need a battery.

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