hard to say for sure what the daily gallon load is, but i would say that it provides water for a dishwasher run 3-4 times per week, hot water in the sink for handwashing probably 6-12 times per day, one run of a washing machine per week, and hot water for showers maybe 10-15 times per year.
so the daily demand is what i would call very low. due to the low demand i am guessing that a heat pump electric could always run in heat pump mode, which is very efficient.
i had not considered a plain electric but i’m open to all ideas. i think the key is to put in something that is best suited to the actual use. and, of course, most economical in the long run based on the actual use.