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Domestic photovoltaic

AlbeAlbe Posts: 135
edited July 2021 in The potting shed
In a different thread there mention of PV being too expensive.

Not sure anyone is interested but here a financial breakdown of our domestic photovoltaic.

Some facts:
*) our system is very large, 9135 Wp. If it was smaller, the finances would be better: the cost scales (nearly) proportionally to the size of the system: smaller system give less feed-in (which at 10 ct/kWh is less financially interesting) but almost identical own use (which at 32 ct/kWh is more financially attractive). 
*) our roof faces East and West, not South. This means we produce less, but a much larger fraction of what we produce can be used by us.
*) currency is € because we are in Germany, I doubt things in the UK are significantly different.
*) I am assuming 3% yearly inflation in the grid price
*) Here in Germany there use to be income tax on both what you use yourself and what you sell to the grid. It was extremely small because every year you could offset 1/20th of the initial cost. This tax is now abolished. Now idea in the UK.

Cost: 10995 (full cost 13084, but we recovered the 19% VAT because when you install the system and start selling your unused electricity to the grid, you inevitably become a business)
Loan interest, 2% over 20yr: 2199
Production: 6560 kWh/yr (not an estimate from a greedy vendor, I measured this myself over the last 365 days)
Own use: 1089 kWh/yr * 32 ct/kWh = 349 €/yr = 9074 € over its 20yr lifespan (also including a 3% grid inflation)
Sold to the grid: (6560-1089)*10 ct/kWh/yr = 546 €/yr = 10920 € over its 20yr lifespan
Replacing the inverter after its expected 10yr lifespan: 2000€

20yr summary:
Total cost: 10995 + 2199 + 2000: 15194
Total earning or savings: 10920 + 9074: 19994
Net: 19994 - 15194 = 4800 €

The financial aspect is not the drive to do this. But if you do do it, it pays itself off and even give a small plus.


  • AlbeAlbe Posts: 135
    edited July 2021
    Again: these are not numbers from a greedy vendor or a glossy magazine. Everything is measured by me and I trust it. Could be I made mistakea. If so, apologies and thanks if you tell me.
  • AlbeAlbe Posts: 135
    edited July 2021
    The environmental aspect is probably not as good as some green fanatics claim, because manufacturing delivering installing the modules on the roof, and eventually disposing, of course causes some damage to the environment.
    My bet is that the overall environmental net is still more good than harm.
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