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Thread: domestic photovoltaic battery

  1. #1

    domestic photovoltaic battery

    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

  2. #2
    Grandmaster Stagger's Avatar
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    Best bet is to call Dura cell or Everyready.
    A quote,

    "The greatest accomplishment is not in never falling, but in rising again after you fall."

  3. #3
    Master molehill's Avatar
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    Afraid I don't understand electricity, in the slightest, so can't comment on your problem. Other than it appears things are not as straightforward or easy as they seem when it comes to "going greener" for energy?
    Ring-a-ring-o-roses, a pocket full of posies, a-tishoo! a-tishoo! we all fall down.

  4. #4
    Master Wheeze's Avatar
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    You're missing the point Alberto. It's not about saving money but saving the species. Innovation costs. Hats off to you for doing it.

  5. #5
    Master Witton Park's Avatar
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    Quote Originally Posted by Wheeze View Post
    You're missing the point Alberto. It's not about saving money but saving the species. Innovation costs. Hats off to you for doing it.
    The intent to save the species perhaps, but on flawed information from the sounds of it. And there's the concern. How many kippers are we being sold?
    Richard Taylor
    "William Tell could take an apple off your head. Taylor could take out a processed pea."
    Sid Waddell

  6. #6
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    I think you will find you are paid under FIT for all you produce, whether or not you use it.

    My system with battery saves me 600 a year electric fuelling all electric for 10 months , including all hot water for six months ( I still have a hot water tank and switch to electric water in summer) , so reducing all summer gas cost. It fuels a heat pump drier ( good for runners) and cooking as well. Could fuel an electric vehicle when I get one. I get around 250 -300 FIT payments. Total cost around 12000 By the time I renew batteries they will be as cheap as chips. So as an investment for return it is hardly exciting, but nothing else is. For anyone with cash it is worth it. Not if you have to borrow.

    I’m about to put in upstairs heat pump heat/cool for air con winter heat. Works well in my other house in Portugal.

    Solar is also perceived value added when and if I sell the house.

    There are also peer to peer energy markets appearing, that should give return better than FIT. Watch this space.

    Quote Originally Posted by Gambatte View Post
    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
    Last edited by Oracle; 28-06-2020 at 09:50 PM.

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