5 ms·

That depends on your generation capacity and what the rules of your grid are. If you're capable of producing enough power to run your home most of the time, th

That depends on your generation capacity and what the rules of your grid are. If you're capable of producing enough power to run your home most of the time, then being grid connected and buying peak load from the grid itself rather than browning out your own devices might be a worth while tradeoff. Most of us with grid tied solar installations (like me) transparently buy and sell electricity to and from the grid depending on day conditions. I buy from the grid overnight, and sell excess capacity during the day. Depending on how much electricity you use a battery system will smooth those out, but you need a lot of batteries to eliminate the need completely (OP mentioned 48KWh, which is about 3.5 Power Walls). In my area the grid is really reliable and fees are low, so buying batteries is not economically viable. I'm currently paying $5.24 per month for a grid tie, which is below my threshold for caring.

PaulDavisThe1st 5y ago
It's also more viable to be grid tied if your winter needs are more than X times your summer needs. My 6.6kW array generates roughly 3x what we need during summer. But our home is heated in winter (at 6000' in New Mexico) using electrically powered air-source heat pumps (aka "minisplits") and that takes about 3x what we generate during the winter. Adding either on-site storage capacity or sufficient additional panels to cover our winter needs really makes no sense. The storage capacity would have to be immense, because no matter how you slice it and dice it, we do not generate enough power to heat our home for several months (and that's with adobe and some passive design). The additional panels would take up a large amount of ground space, and result in us generating 9x our needs in summer. I prefer to put my faith in the emergence of grid-scale storage solutions than try to solve this on a just-my-home level.
- ashtonkem 5y ago
  If the grid wasn’t reliable, a hypothetical I know, it would probably be cheaper to switch over to a ground source heat pump rather than increase your panels by 3x. That would lower your winter electricity demand, albeit at the cost of significant capital expenditure.
  - PaulDavisThe1st 5y ago
    Does a ground source HP use that much less electricity than an air source HP?
    - ashtonkem 5y ago
      Yes, by far. It’s much easier to extract heat from ~55F ground water than from ~20F exterior air. Ditto for dumping excess heat into ~55F ground water than 90F exterior air. On average the water coming out of a geothermal loop will be more advantageous to work with than exterior air, which is why it’s a thing.

PaulDavisThe1st 5y ago

It's also more viable to be grid tied if your winter needs are more than X times your summer needs. My 6.6kW array generates roughly 3x what we need during summer. But our home is heated in winter (at 6000' in New Mexico) using electrically powered air-source heat pumps (aka "minisplits") and that takes about 3x what we generate during the winter. Adding either on-site storage capacity or sufficient additional panels to cover our winter needs really makes no sense. The storage capacity would have to be immense, because no matter how you slice it and dice it, we do not generate enough power to heat our home for several months (and that's with adobe and some passive design). The additional panels would take up a large amount of ground space, and result in us generating 9x our needs in summer. I prefer to put my faith in the emergence of grid-scale storage solutions than try to solve this on a just-my-home level.

ashtonkem 5y ago
If the grid wasn’t reliable, a hypothetical I know, it would probably be cheaper to switch over to a ground source heat pump rather than increase your panels by 3x. That would lower your winter electricity demand, albeit at the cost of significant capital expenditure.
- PaulDavisThe1st 5y ago
  Does a ground source HP use that much less electricity than an air source HP?
  - ashtonkem 5y ago
    Yes, by far. It’s much easier to extract heat from ~55F ground water than from ~20F exterior air. Ditto for dumping excess heat into ~55F ground water than 90F exterior air. On average the water coming out of a geothermal loop will be more advantageous to work with than exterior air, which is why it’s a thing.