Simple home device needed to monitor electric usage

Suppose you were filling your car with gas, and the pump behind you suddenly changed the price from $4 a gallon to $400 a gallon. You’d get an unpleasant surprise when you put the nozzle back on the hook and saw how much you owed.

Electric prices can go up 100-fold during an unexpected shortage, as they did in Texas in 2021. Price spikes of this magnitude are fairly common in the electric market (although usually much shorter-lived than they were in Texas), because heat waves, cold snaps and unexpected outages are not predictable. The Texas situation was unusual both because it was prolonged,...