A small battery (10kWh) might even make sense soon - if you're still using 10kWh of power in the winter evenings, you could avoid 10 * $0.12 = $1.20 of lines charges each day by charging the battery at the offpeak rate and using it during the peaks.
Maybe. I just looked at a random winters evening, we used 13kwh of power at around 13c/kwh, though some was lower at 10c/kwh. Overnight rates were 8c/kwh. Battery and inverter technology will probably have to get a lot cheaper before that narrow margin makes sense. Install costs could be expensive too It may make more sense when power prices are higher, later summer when the lakes are dry.
Heat pump driven night store may make sense, but that takes a lot of thermal mass to be worthwhile.