The future?

MikeRM

Looking a bit further into the BYD batteries, in addition, you need an inverter, and control gear. I think that would work out more expensive than a Powerwall 2, assuming you can get anything equivalent to the Gateway2.

MikeRM

You got fleeced.

BYD Battery-Box L14.0

That 14kWh so a little more than Tesla. £6,500 inc VAT, plus installation and an inverter.

More interesting though is the fact that they are modular. They do module wall mounted ones as well as free standing. So you can start with a smaller system and scale up over time, buying more modules as budget or need allows.

MikeRM

The Powerwall 2 can also be wall mounted and is modular, in that a second can be mounted in front of the first. A friend has 4 PW2's mounted in pairs, about 300mm deep (he has a very large demand!). The inverter is built into the PW2 which has just gone up to £6650 inc VAT, so the PW2 is cheaper although the single fixed size is 13.5kWh. That is about right with a 4kW solar array in a normal house, maybe a bit big if demand is fairly low. However, given that Tesla is competitive I think the main question is whether other systems have as advanced software control as Tesla. It depends what your requirements are. Fully off grid or backup only are different to a normal on grid house with solar, and individual power requirements are very important in sizing.

MikeRM

Looking at the Specs and warranty, the BYD is warranted for 10 years as is the Powerwall 2. But the Byd warranty is for 60% of original capacity whereas the Powerwall 2 is for 80%. That seems to tie in with the conditioning systems. The BYD is "natural cooling", passive air cooling, in other words. The Powerwall 2 has active liquid cooling. In other words the same as the Model S and Model 3 battery conditioning systems. It is maintained at the optimum temperature for charging. That is why the Model S, and by inference the PW2 have a much longer battery life than the Nissan Leaf, which has no active conditioning. My Model S has lost 3% in 4 years/50,000 miles and most of that was in the first few months, as is normal with lithium ion battery life. It's hardly changing at all now. I expect to get at least 15 years useful life from my Model S battery and probably much longer (I'll probably be dead or at least handed in my licence by that time!). I suspect the difference in warranty conditions is related to the conditioning systems. The PW2 can be expected to last a lot longer than the BYD. So it's like comparing apples and oranges.

Out of interest, here's a review of the PW2 and comparison with other batteries. It's from 2016 so a bit out of date but the cost per total warranted kW is shown to be lowest for the PW2 and highest for a BYD battery (not the L14.0)

Powerwall 2 Full Specs Reveal Cheap Storage And Limited Warranty