They don't actually say what the efficiency of it is, only that the inneficiency is mainly heat and "70% of home energy needs are for heat" which makes sense in Scandinavia but makes less and less sense the further South you are, plus it massivelly depends on being able to capture and use that heat (can you use it for cooking or only for environmental heating?).

Ultimatelly efficiency and price are what makes almost all the difference.

That said, I hope this turns out to be a proper solution: we definitelly need home energy storage solutions which have much higher energy density and lower cost per mWh that the ones we have now.