I can see two potential niches for it. First, those plagued by frequent power cuts may find a home battery appealing, as it would let them ignore the shorter ones and gracefully prepare for the long ones. It might also be a money-saver, as you could charge it off-peak for use in the day - the youtube tinkerer PhotonicInductction does exactly that, and has run through the calculations to determine it can be economical. Even with the efficiency loss, the price difference is enough to justify operating the battery. The payback time would be poor, I expect - but a lot better than those rooftop wind turbines, and people are suckered into buying those.