Hot Water - 3 Fuel Sources - Baseline Model

You would model a gas hot water heater in the baseline and you'd model the proposed as designed.

A slight amendment to Anthony's suggestion - model the baseline for the heat pump as electric water heater and the baseline for the boiler as gas water heater. The solar is all savings!

Anthony, We had the same question as Fabiano's a few days ago and we found in ASHRAE 90.1-2007, Appendix G, 11-Service Hot-Water Systems that: "The service hot-water system in the baseline building shall use the same energy source as the corresponding system in the proposed design..." So we concluded we had to model the solar water heating system in the baseline. I'm confused now...

Solar hot water is considered "on-site renewable energy" and should be modeled in the proposed only, as it is a savings. Report the savings in the appropriate section in the EAp2 template. you should be good to go!

I can't find any LEED Interpretations on the subject, but I've always handled DHW systems similarly to HVAC system types. So for example, if the proposed building had a hybrid (gas/electric) HVAC system, you would use gas in the baseline. Similarly, if my proposed DHW system is a hybrid, I would use gas in the baseline. I agree that the user's manual doesn't really clarify this issue, so my guess is that either approach would be acceptable to GBCI.

The GBCI reviewer will follow the guidance in Table G3.1-11 Baseline that was quoted by Marcio above for the baseline service hot water (SHW) systems. "The service hot-water system in the baseline building shall use the same energy source as the corresponding system in the proposed design..." This language is pretty clear. SHW does not follow the same baseline guidance as the HVAC systems. The solar hot water is addressed by the Exception to G2.4 which indicates that you use the back up source for the baseline when using an on-site renewable in the Proposed.

You're right, I started reading at bullet "a" which wasn't helpful.