Comment on ‘If 1.5m Germans have them there must be something in it’: how balcony solar is taking off

• Buffalox@lemmy.world ⁨1⁩ ⁨week⁩ ago

  Thanks. 😀
  Going off grid was absolutely a consideration, but only for a very short while. There are too many downsides. We would need twice as much solar capacity, and a way bigger battery, and batteries are still pretty expensive, but even with that, we would still need a generator. And we wouldn’t be able to sell surplus energy. It would more than double the cost, and only provide 25% better self sufficiency for the whole year than we have now.
  We live in Denmark, and we can risk to have to go through almost all of December with only a few days sun. Running a diesel generator for power would be both noisy and smelly, It would also require more work to maintain, and it would actually cost slightly more to us a generator than to simply buy the electricity from the grid.

  Remember doubling our capacity will not bring us from 41 to 82% self sufficiency. Because there is some loss in storage, and even double our battery capacity would not be enough to store 48 kWh like we made today in the span of only 7 hours. (Today was the best day of the year yet. 😎)
  Even in January on a perfect day, we can make twice what we use, but such days are rare in January. (we use about 15 kWh per day.)

  The final problem with a generator is that we would never be able to achieve remotely the stability we have with the grid. We’ve been living here for 6½ year, and the power has only been out once!!!

  The problem with making it bigger than we have at all, is that after you’ve reached a point of above 50% self sufficiency, you are entering the area of diminishing returns quickly. On a yearly basis we are about 72% self sufficient. To reach that extra 22% probably cost 50% extra.

  This is if you live as high north as we do, because the extra capacity is only usable in the winter, in the summer it’s all surplus, and you get so little for selling the power it’s basically irrelevant. There is too much solar now, so when solar panels have high yields, prices often go down to almost zero.

  source

  • Valmond@lemmy.world ⁨1⁩ ⁨week⁩ ago

    Thanks again for all the information!

    Yeah, going off grid is a whole philosophical idea in itself, way smarter to share with the grid if you’re not in some very specific situation IMO.

    I always thought that those calculations about solar was a bit bogus, like you extrapolate the earnings today over say 12 years to pay off an installation, of course it will get cheaper in the future and as more people have solar, revenu goes down too. Seems you solidify that idea!

    Today though it starts to be almost a criminally good investment… Living in an appartment I seriously think I might get one of those balcony panels this year, just gotta check out how it actually works when ju inject that into the system. We redid all the electricity so we have separate lines for about everything, will the sun powered line hop over to another one (they are after all all tied together at the central input) and how many amps can you allow to flow “backwards” like that and so on.

    source

    • Buffalox@lemmy.world ⁨1⁩ ⁨week⁩ ago

      will the sun powered line hop over to another one

      This is why you need a new meter, at least that was the situation for us. If we didn’t get a new meter, we would only be able to use one line, and the surplus would go to the grid.
      They actually forgot to tell us that, so after some very confusing analyzing of what the fuck was wrong, I complained that the system didn’t work, most of our generated power was sold, and then we had to pay to sort of buy it back!!
      This was all down to the meter not being replaced for one that was meant for handling local production properly. We basically lost 3 months of production on that account. After we got the new meter, it worked perfectly, and production is as advertised, and I was very happy to see that production in winter was almost exactly as I’d calculated: 😎 Although obviously you can’t calculate the number of sunny days in advance.

      Something that surprised me, was that in the summer, production is still reasonably good even on days where the sky is completely overclouded, as long as the clouds are white, enough light penetrates so we can still achieve almost half the full capacity.

      Another fun story IMO, is that we switched electricity supplier February last year, and they work with advance payments, and since we were new customers, we got a bill for 3 months of normal use. We just received the “bill” for 2nd quarter, with negative payment amount, because there is still money left from our advance payment! 😋 AND that is without sales, which is a separate account, but is only about €15 per month on average. (for selling 7844 kWh for the year 2024) So about 2 cent per kWh on average.

      source