We saw discussions for the water heater, but am still not sure if the hot water heater applies to the calculation for this credit.

According to the reference book, “The credit applies to all installed equipment and appliances listed by the ENERGY STAR program. Any categories added to the ENERGY STAR list in the future may be used in the project team's calculation.”

It seems that “Water Heaters” are added as a new category to the Energy Star website, and they are not HVAC, lighting systems, and building envelope products.

So, water heaters should be included to this credit. Is my understanding correct?

If so, you need to demonstrate the water heater installed is equivalent to the Energy Star-qualified product. However, our water heater is an electrical instantaneous type without tank and we could not find any such type in the Energy Star web site. In that case, it does not need to be included in the calculation as it is not classified by Energy Star (CIR #10044)?

In general, if the subject equipment and appliances are classified by Energy Star, should they be included to the calculation even though no product is available locally or they are custom-made?

Our project is a tenant fit-out in an office building and the water heater is used for a shower.