My wife had refused point blank to even consider solar panels on the roof. Converting my all-electric house to gas was not only a non-starter from a cost viewpoint but arguably was heading against the flow of government policy to get rid of gas boilers. That only left a battery solution. (Not interested in a wind turbine or an air source heat pump).
Eventually, I recently went for a Tesla Powerwall 3. It claims 13.5kw-hrs capacity, but I've seen it charge over 15kw-hrs. Probably so it still delivers 13.5 after ten years. I justified it on the difference between my day rate and my night rate charges for electricity with my then energy supplier. But two things have reduced the payback period dramatically.
The first is that I found a supplier that I could not have used before the battery because its day rate and standing charges were so high that they offset the cheap night rate. However, now that I am forecasting to be above 90% night rate (instead of 73%) over the year, that supplier's rates have dramatically increased the savings. .
The second thing is that I can often take advantage of the larger than advertised battery capacity to time shift even more energy to a cheaper rate. But I can't offset more energy that night than I have used that day, because if I don't start the night rate with an empty battery, then charging can only top it up.
I expect to be saving in excess of £140 per month vs my previous best alternative, pre battery.
The Tesla also comes with automatic back up, switching over in 20ms in the event of a power cut. The Tesla has rapid charging and discharging, many batteries don't.
I have a 3-phase 415V power supply and the Tesla is not 3-phase. There is no reason why you need a 3-phase battery to match the 3-phase power supply, just use one of the phases, the same way the domestic power does. But the wiring up and the integration is not as straightforward. It has been one month since the battery was installed and I am still not 100% convinced that the installation is working exactly as it should. The battery supplier is very good indeed, being very supportive. But I have a new energy supplier that was keen to get me on a smart meter until they discovered that I'm 3-phase. Octopus Energy are trialling 3-phase smart meters, but that's about it, my supplier isn't. So right now, I'm stuck with a mechanical timer and meter, which makes finding out exactly what is happening a bit more difficult. The problem is that my usual summer time 5kw-hrs of night rate usage seems to have disappeared. It looks as though either it is not being recorded (ie I'm not paying for it). Or, it is going through the battery, which means that my extra time shifting is reduced by 5kw-hrs per night (most likely). Which means that my savings will be reduced. I will get to the bottom of it.
