We built our house in 2019 and at the time we got photovoltaic installed. I expected during their 20yr lifespan to even out the initial cost of purchase and installation, at best. Now after harvesting daily data over 7 months of operation I know they will not. Never mind.
We opted for heating the house via gas, rather than heatpump (better for enviroment, hugely expensive to install, cheaper to run). I now regret this choice but so be it.

At the time we installed the PV I though about installing a battery, not right then because their were still astronomical expensive, but in future once the cost dropped.

I now enquired for battery and got quotation for 7 kWh, 20yr warranty, 10k eur.
We could load/unload the battery an average of ca 3 kWh/day. In sunny long summer days we woulnd't exploit the 7 kWh capacity because we already buy from the grid very little. And in cloudy short winter days we also wuldn't exploit it because the PV produces too little to fully charge it. The 7 kWh battery, the smallest I could get a quotation for, is oversized.

For every kWh we load/unload into the battery this would save us 32ct from not buying from the grid, but also lose us 10.64ct for not selling it into the grid.

So over its 20yr lifespan this would save us:
3 kWh/day * (0.32-0.1064) eur/kWh * 365 day/year * 20year = 4678 eur

So paying 10 keur upfront, plus interest, to save 5 keur during the next 20yr.
How can one justify this????????

I know I ignored inflation on the price of buying kWh from the grid. But I also ignored loan interest, and battery degradation. Still a huge loss.

I doubt household PV battery will ever win out economically. Maybe on a boat.... (haven't got any, only a crappy car and many bycicles...)

Any comments?
Cheers,

Alberto