Mr Purcell admits he initially bought his battery as a form of insurance against the volatility inherent in the spot market.
However, his thinking quickly changed when he saw the opportunities on offer, describing one instance in which he was able to fill up his 10-kilowatt-hour battery with electricity costing 1 cent per unit.
“That’s the opportunity and the risk on the very low prices,” he said.
"It cost me 10 cents to fill the battery during the middle of the day.
“And then at night-time the price went up over $10 a kilowatt hour, so I was able to export that same 10 kilowatts out of that battery for $100.”
I recommend spending money on reducing consumption instead of increasing storage.
There can be astronomical savings on the consumption side - for example my gaming PC draws 400 watts, and my Apple Laptop draws, I shit you not, between 2 and 3 Watts with active use and 200 milliwatts while idle. That laptop is more than fast enough for gaming as well (though being a Mac, I can only play some games). A really intense game might push the consumption up to 5W…
Also, I just don’t plug the laptop in unless the sun is shining - I just checked the battery log (Macs have nice charts for power consumption), and I unplugged at 4:45pm yesterday, used it for about 5 hours last night, and it’s still at 70% charge this morning.
Cooking dinner as soon as you finish work makes a big difference too (assuming you’re cooking on electric?). Also it’s probably better for your health to have a longer gap between dinner and breakfast.
If you find savings like that across all your appliances, especially at night, that 10kWh battery will be a lot more useful.
When I lived off grid (long time ago, when this stuff cost more, on a rural property where the power company quoted a quarter million to run a power line to a new house my parents built) we had a 3kWh battery and it was lead acid, so realistically it was more like 1.5kWh of usable storage - we had an automatic cut off at half charge to protect the cells (it could be disabled, in an emergency). That was more power than we needed - it can be done with efficient appliances. We didn’t even own a backup generator and the half charge cut off was only disabled once, when a battery failed (3kWh was six batteries, not one).
I have spent a lot on reducing our usage, and have basically reached the limit. We have good insulation, modern appliances and overall our overnight usage is pretty good. I am not willing to start removing the things that make life pleasant, such as the TV or my gaming PC (and given how little it gets used it hardly matters), and i work until late, so can’t cook any earlier anyway (and i am still predominately on gas).
Overnight our houses idle usage is ~0.3kwh, so the battery can comfortably last the entire night and then some. But it doesnt change the fact that if there is poor weather for a few days in a row, the battery wont be charged from my solar, and then I have to draw from the grid. And if i am on wholesale pricing, that will wipe out any potential profits from the rest of the year.