Agree with @billlokey here though I will add some thoughts:
-
Gone are the days when switching a tank was a straightforward decision … even if longevity vs cost; efficiency (direct resistive vs heat pump) and other factors seem, actually, like factors.
-
Annual kWhr will be significantly influenced by the local water conditions (water temp rise).
-
Hot water generation and STORAGE is a hugely important issue when you factor in the energy storage potential of a (large, well-insulated) tank in a solar scenario.
-
Do you have or intend to have solar?
-
Just like an EV battery or house battery charging is a great way to load shift usage to avoid sending watts to the grid, hot water storage is at least a partial consideration in the future of solar optimization. I harped on this here.
- Instantaneous electric water heating is undoubtedly potentially more efficient than stored heat but the equation is less than trivial when considering embodied energy. Thought experiment: Everybody who is able decides that’s the way to go, instantaneous … the Utilities’ loads become untenable and force grid upgrades. Worst case, a mass consumer decision to convert their water heater results in the need for additional power stations due to synchronized morning ablutions! As a general rule these days, it seems if you can encourage end-user grid-demand CURRENT reduction you are on the right path. “Switch bulbs to LED!”. Same goes for a water tank: heat-pumps use less current (and energy). Caveat: In any given household there is distinct advantage in enabling HIGH current. e.g. quick EV charging. This, however, should be kept as local as possible and not increase grid demand. i.e. high current local solar charging is ideal.
As far as your actual question goes (!): I’m in a constant state of frustration regarding my own hot water supply: small apartment, no solar possible, low current max (100A), small space for water heater. I had to replace my EOL tank a few years ago (1,183 days ago to be precise) and couldn’t squeeze in a then-available HPWH so went with a Rheem Performance Platinum XE40M12EC55U1 with 4.13kW elements at the 208V supply. Energy label is 4,622kWh/yr and for the Sense period I have it monitored it’s clocking in at 2,728 kWhr/year. That’s based on the average of two native Sense detections over 290 days starting March 8th, 2019. This may be close to actual usage (2 people; NYC incoming water temps) but I’m not confident it is. I have data from actual monitoring of my tank that I will post after doing a comparison with the Sense native detection.
