I'm working on an apartment building project for a utility incentive and LEED certification. The baseline model uses PTACs (90.1 PRM System 1) and the proposed model uses WSHPs. Comparing just the HVAC system differences, I haven't found that the WSHP system is much better in terms of energy cost or use. So my question is whether other modelers have found significant differences in energy cost or use when comparing these systems?
The problem I've found is that while the gas usage is less with the WSHP system, there is an electricity penalty for switching from all gas heating in the PTAC system to gas and electric heating in the WSHP system. So while the EUI of the WSHP system is similar or lower than the PTAC system, the energy cost is higher due to the price difference between gas and electricity. I haven't found a "big lever" to pull in the proposed model, such as plant temperatures, that will alleviate this issue. Any thoughts?
