What makes a heat-pump water-heater quote hard to compare?

I’d ask what peak-use pattern each estimate assumes, not just the household’s average daily demand. A household that draws several showers close together may need a different recovery or storage assumption than one using the same total amount spread through the day. That can affect sizing and projected operation, so quotes are easier to compare when the assumed busy period and draw timing are stated.

I’d give a realistic assessment of the proposed location and expected noise at least as much weight as a favorable efficiency estimate. A quote’s projections are hard to compare if one assumes a room and placement that suit the unit while another accounts for room-air needs or proximity to living and sleeping areas. Alongside the peak-use pattern, I’d want each estimate to state the location assumptions behind its numbers.

I’d prefer those items to be listed separately, even if some are included in the base price. Otherwise, a lower total can look like a better comparison when it may simply leave electrical work, condensate drainage, or ducting outside the quote. Saying “included,” “not needed,” or “not included” for each would make the scope clearer without requiring every estimate to use the same setup.

For savings projections, I’d also ask what electricity price and hot-water usage assumptions they use. Two estimates can describe the same unit and location but show different savings if one assumes a cheaper electricity rate or a different pattern of use. Stating those assumptions makes the projections easier to compare, rather than treating the largest savings figure as automatically the best fit.

Would it help to ask for two savings projections: one using the same electricity price and usage assumptions across quotes, and another based on the household’s expected use? That would make the comparison fairer while still showing which estimate better fits the household.

Yes - those two views serve different purposes: a common-use projection helps compare quotes on the same basis, while the household-specific one is more useful for judging likely fit. I wouldn’t treat the shared projection as a complete apples-to-apples comparison unless the assumed operating conditions and proposed location are also made clear; those can affect the estimates too.