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What is "expensive"? I've invested 35.000 Euros into a 12 kwp PV system with 14kw/h in battery storage three years ago and I'm on track to recoup within 10 year

by tfourb 2y ago

What is "expensive"? I've invested 35.000 Euros into a 12 kwp PV system with 14kw/h in battery storage three years ago and I'm on track to recoup within 10 years. For me it works because I have a 60%+ share of usage (in contrast to feeding into the grid), heating my home and powering my car. A smaller system (i.e. 3kwp, no storage) will break even within 10 years for basically everyone, if you can buy panels at usual market rates and have energy prices in excess of 25 Cents/kwh. But in Germany basically no new residential building is built without at least 8 kwp rooftop solar due to quite generous subsidies for capital costs and feed in tariffs.

hnaccount_rng 2y ago
The limiting factor for small systems is the one-off cost of the installation. You necessarily need to have this done by a certified person and that needs to go to your place and $DO_THINGS. That doesn't matter at 35kEUR, but it does at 5kEUR. But yes in Germany I think even pure grid batteries should pay for themselves with variable price tariffs. If you would only pay for the battery. But that only holds if you need to have an electrician there anyhow. That also explains why every _new_ building gets solar (not sure about the frequency of batteries)
- tfourb 2y ago
  If installation cost is a limiting factor, you can do a lot of it yourself. A friend of mine had installed 15+ kwp, including running wires, with the electrician only doing the final wiring and verification, which drastically cuts down the costs.
  - hnaccount_rng 2y ago
    I don't think that helps you very much, we are talking 2-3kEUR hardware costs. Even getting that person to your place and back will add significant percentages of overhead. And even going to smaller systems (that you apparently just plug in here in Germany, see sibling comment) are already getting too expensive to really work-out even under ideal assumptions
- tfourb 2y ago
  At least in Germany, small systems up to 0.8 kWp can be connected to any household without any professional installation and these systems are available as "plug and play" packages.
  - hnaccount_rng 2y ago
    Ah interesting, I wasn't aware that you can put Balkonkraftwerke _with_ a battery on a normal outlet, too. Thanks for that. I don't think that changes my conclusion though, as the per-kWh-price there is significantly higher (I think mostly due to the transformer that's required) :/ I did the calculation for another discussion yesterday. For larger battery systems you can get 10kWh for about 2.4kEUR and with that 240EUR/kWh the battery would amortise itself quite quickly (6 years, ignoring interest [0]). But the Balkonkraftwerk batteries are more 1.6kWh (+ 1000W panels) + transformer for 1kEUR. The solar generation changes the calculation a bit [1], but if I ignore that then we are at 625 EUR/kWh, which would at least double, maybe triple the payback period (and then ignoring interest becomes much more relevant). However this is largely academic as for my calculation you'd need to use more than 20kWh per day (2 cycles @ 10kWh). The cheapest battery-only normal-outlet system I could find was 900 EUR (but the AC/DC transformer is already included) for 1.6kWh, so 562 EUR/kWh. I don't think I even use the 3 kWh/day for that system... And we are talking <100 EUR/year savings. In the end (residential) electricity is just not that expensive (in terms of household budget) [0] With a dynamic price rate you could do two cycles per day (loading in the night and at midday with lack-of-demand-cheapness and solar-cheapness) on 250 days/year and a spread of 8ct/kWh (there is some variation, but that should be somewhat conservative) you can get 500 cycles/year and about 40EUR per battery-kWh installed. [1] In the calculations above I took a rough look at the pricing data in Germany https://www.energy-charts.info/charts/power/chart.htm?l=en&c=DE&week=11&year=2025&source=total&legendItems=2wgw2w2 https://www.energy-charts.info/charts/power/chart.htm?l=en&c... and picked numbers for reasonably simple calculations. With solar you would essentially do the Midday charging for "free" from the panels, increasing the price spread in the evening. One could also take time-of-use rates for the calculation, which (currently) typically offer a structure of -6ct, -6ct and +4ct at night, midday and evening (vs morning prices)
    - 2y ago

by tfourb 2y ago

hnaccount_rng 2y ago

The limiting factor for small systems is the one-off cost of the installation. You necessarily need to have this done by a certified person and that needs to go to your place and $DO_THINGS. That doesn't matter at 35kEUR, but it does at 5kEUR. But yes in Germany I think even pure grid batteries should pay for themselves with variable price tariffs. If you would only pay for the battery. But that only holds if you need to have an electrician there anyhow. That also explains why every _new_ building gets solar (not sure about the frequency of batteries)

tfourb 2y ago
If installation cost is a limiting factor, you can do a lot of it yourself. A friend of mine had installed 15+ kwp, including running wires, with the electrician only doing the final wiring and verification, which drastically cuts down the costs.
- hnaccount_rng 2y ago
  I don't think that helps you very much, we are talking 2-3kEUR hardware costs. Even getting that person to your place and back will add significant percentages of overhead. And even going to smaller systems (that you apparently just plug in here in Germany, see sibling comment) are already getting too expensive to really work-out even under ideal assumptions
tfourb 2y ago
At least in Germany, small systems up to 0.8 kWp can be connected to any household without any professional installation and these systems are available as "plug and play" packages.
- hnaccount_rng 2y ago
  Ah interesting, I wasn't aware that you can put Balkonkraftwerke _with_ a battery on a normal outlet, too. Thanks for that. I don't think that changes my conclusion though, as the per-kWh-price there is significantly higher (I think mostly due to the transformer that's required) :/ I did the calculation for another discussion yesterday. For larger battery systems you can get 10kWh for about 2.4kEUR and with that 240EUR/kWh the battery would amortise itself quite quickly (6 years, ignoring interest [0]). But the Balkonkraftwerk batteries are more 1.6kWh (+ 1000W panels) + transformer for 1kEUR. The solar generation changes the calculation a bit [1], but if I ignore that then we are at 625 EUR/kWh, which would at least double, maybe triple the payback period (and then ignoring interest becomes much more relevant). However this is largely academic as for my calculation you'd need to use more than 20kWh per day (2 cycles @ 10kWh). The cheapest battery-only normal-outlet system I could find was 900 EUR (but the AC/DC transformer is already included) for 1.6kWh, so 562 EUR/kWh. I don't think I even use the 3 kWh/day for that system... And we are talking <100 EUR/year savings. In the end (residential) electricity is just not that expensive (in terms of household budget) [0] With a dynamic price rate you could do two cycles per day (loading in the night and at midday with lack-of-demand-cheapness and solar-cheapness) on 250 days/year and a spread of 8ct/kWh (there is some variation, but that should be somewhat conservative) you can get 500 cycles/year and about 40EUR per battery-kWh installed. [1] In the calculations above I took a rough look at the pricing data in Germany https://www.energy-charts.info/charts/power/chart.htm?l=en&c=DE&week=11&year=2025&source=total&legendItems=2wgw2w2 https://www.energy-charts.info/charts/power/chart.htm?l=en&c... and picked numbers for reasonably simple calculations. With solar you would essentially do the Midday charging for "free" from the panels, increasing the price spread in the evening. One could also take time-of-use rates for the calculation, which (currently) typically offer a structure of -6ct, -6ct and +4ct at night, midday and evening (vs morning prices)
  - 2y ago