In my case, I'm already using pretty much all my solar energy. So it's not that big of a deal for me honestly.

I'd like a hot water tank like that, but I don't really have the attic space to place it near my boiler. I have a gas powered CV unit, so I already have on demand hot water. Ideally I'd replace it for a hybrid boiler that would work of electricity until demand exceeds electric capability. But it's still well within its lifespan.