How does one find a more energy-efficient water heater from similar models?

Question

I recently purchased a

Rheem Performance 40 Gal. 6 Year 4500-Watt Elements Electric Tank Water Heater (model # XE40M06ST45U1)

to replace my

GE 40 Gal 4500 watt Electric Water Heater (Model # GE40M06AAG)

I was quite pleased when I saw the yearly energy cost on the Rheem water heater at $419

and my old GE water heater's yearly energy cost at $$508.

That's an $89 saving a year!

But upon closer inspection, I notice the Rheem water heater's yearly energy cost [$419] is close to the upper end of the energy cost of similar models. While the GE water heater's yearly energy cost [$508] is a little to the left of the midpoint of similar models. Clearly, the new Rheem water heater is more energy-efficient than the GE water heater. Then why is the Rheem's yearly energy cost at the upper end of the cost of similar models?

It's my understanding that these two water heaters are similar because they both hold 40 gal and use 4500 watts. How does one find a more energy-efficient water heater from "similar models"? Where does one begin to look for similar water heater models?

Answer 1

The low end of the scale for the new one is clearly based on heat pump water heaters. Which cost a great deal to buy, and add to your heating bill in winter unless they cost an even greater deal. Which is not really "similar models" at all. Presumably similar in tank size or something. The old one is just different resistance heaters, for a much narrower range.

Actual "Similar models" have changed over time to be "generally better insulated" (and that, plus heat traps, is about all there is to resistance electric efficiency. Add more insulation once it's in place unless your instructions prohibit that. Insulate pipes well, too.)

Incidentally, the old one provides that estimate based on 10 cents per kWh and the new one based on 12 (actual "estimated" use is 4473 kwWh/yr old, 3493 kWh/year new, so the insulation is considerably better; or the use amounts have been reduced for the estimates.)

I bought a water heater last year. I needed a short one, or it was going to be located poorly. Conceptually I like the heat pump ones (I heat my house with heat pumps) but practially - they are all tall form factor, they get that low operating cost partly by not counting what they add to the space heating bill, (but you get some free A/C in summer) and longevity of complex items to offset the high inital cost is dubious compared to simple dumb resistance heat. So I have a short resistance heater and plans for an eventual wood boiler and solar thermal hookup.

Tankless electric is frankly stupid. You need a boatload of power to make them work, which often requires a service upgrade, and even then they have considerable flow limitations. All to save the rather minimal standby losses of a (modern, well-insulated) tanked electric resistance heater. Tankless gas can make sense.

Answer 2

To support Ecnerwal's answer, just look at the spread. On the old heater, the "scattershot" is quite narrow - $492 to $531, or less than an 8% spread. That is because they are all exactly the same thing: resistive electric heaters which are 100% efficient right on the button, and the only differences are quality of insulation.

The new heaters are subject to government requirements for improved insulation, so we expect that to be better.

Whereas on the new heaters, you have a scattershot of $120 to $423, or about 330% of scattershot. Realistically, the resistive heaters certainly have that same tight 8% spread ($390 to $423 for instance). So the low end is clearly some other tech. There's no doubt that it is heat pump water heaters, which are new.