Glan gluaisne
Active Member
With our 4kW array and 3.6kW inverter, we also have a solar diverter to send all surplus electricity to our immersion heater rather than the grid (we are all electric). Having storage batteries would make no sense as we have no surplus energy, and none goes back to the grid. During summer when it's hot, the air-con is working hard to keep us cool (for free).
We have a bit over 6 kWp of PV, an all-electric house, and a diverter to store heat in a "thermal battery" to heat our hot water (it's a phase change sodium acetate based thermal storage unit). Likewise, having batteries makes no sense, I can't quite get the very cheapest system available to cover it's purchase cost, with me doing the installation, before it dies from old age.
We also find that running the house cooling systems from free electricity in summer is probably the best use we get from the PV, along with water heating and a bit of summer car charging. PV really doesn't deliver much for the time of year when we use most of our electricity, and delivers way too much at the time of the year when we don't use much. It's not at all uncommon to find that, on a hot summer's day we're sitting with the thermal battery fully recharged by mid-morning, the car charged, the house cooling system running and we're still pumping over 4 kW to the grid in excess generation.
If there was an affordable way to store around 2 MWh or so of electricity, then we could store enough excess during the sunny months to keep us going through the winter months, but such a technology doesn't yet exist, and if it did it probably wouldn't be batteries. Something like a very much larger version of our thermal battery might work, as that has a much longer life than batteries, with seemingly no degradation with age.