I’m planning to cut my grid connection and go full off-grid. Which raises the question of how much capacity I really need. And what you see here is me trying to answer that question based on ~51,000 5-minute data points of usage data my power company provided to me, complete with custom-made python script to parse all that data and pretty charts! (Yes, I have 6 monitors. And this kind of shows why.)
And what I’m really torn about now is how much battery capacity I need. Should I get enough to cover the absolute worst case scenario (~66kwh) or is something closer to my average overnight usage (~20kwh) acceptable?
Not the absolute end of the world if the batteries run dry and I need to temporarily supplement with generator backup, I suppose. Nobody is life-or-death depending on any electrical appliances here, and even on the coldest days, waiting a few minutes to go start a generator isn’t a huge deal.
But definitely would like a word from the wise about how much battery capacity I really need. And also how much solar panel wattage I need, I suppose.
We live in North Scotland in an old house that has solid walls with no insulation, with about 300mm of roof insulation.
40kwh of batteries.
Heatpump with ufh.
8kwh of solar panels.
What we were told with the batteries is that we can’t use all of them. You have to leave about 10 percent in them at a minimum or you may damage them. So factor that in.
Heating is through a heatpump. And log burners when it’s really cold. In the last winter we had it at -11c at times. It’s quite windy and stormy at times up here.
Solar panels. They don’t really put out any power in December or January. We were lucky if we were getting 1 kWh a day in January…
Though they do power us most of the spring, all summer, and most of autumn. Basically from the middle of November, December, January, February, and the middle of March we need to supplement from the grid because of the heating. Though if I lived alone I wouldn’t need to supplement any power in most of Nov, or Feb. But as I live with people who really feel the cold we need to have the heating on even during the warmer days of March.
If we didn’t have a heatpump then we’d hardly need to supplement at all as our daily electricity usage is about 12kwh. But then we’d need to use heating oil etc etc.
If we were to try to go off grid then we’d need to get rid of the heatpump AND have to at least triple our solar panels.
We were projected by, I think, OpenSolar project to be able to produce 4kwh a day in Dec and Jan with our panels but in reality in the whole of December we produced about 50kwh and in Jan it was less than 30kwh for the month (though it was a really bad in Jan. The worst weather for nearly 20 years.)
Our daily electric usage in December and January with the heatpump was about 50kwh. Which means what we produced in the whole of January and December wouldn’t power and heat us for 2 days…
Over the next year we will be insulating the house and roof etc as much as possible. So, hopefully, next winter we won’t need nearly as much heating. Hopefully. Have you noticed I used the word hopefully a lot…?
I want to go off grid but I don’t know how.
It’s either, get rid of the heatpump and triple the panels, which we don’t have the land for. Or a wind turbine.
If we go the wind turbine route then we’d probably need a 5kwh version to produce about 2kwh. And I think the 5kwh ones are expensive. Though we may get away with a smaller turbine once the house is insulated.
No idea if I’ve helped, but if not then hopefully you’ve got a few ideas to think about.
In the perfect world we would’ve spent the first year here insulating everything as much as possible. Then look at the heating etc. Unfortunately time constraints meant we needed to do the windows and doors then renovate the inside first. Hindsight is a great thing.