I'm a BEOpt novice, for code review doing modeling of a DOE prototype single-family w/ a federal minimum heat pump (8.2 HSPF, 14 SEER). Climate Zone 4, central Virginia. Envelope is code-minimum for Virginia.

The fraction of heating energy provided by supplemental/resistance heat is vanishingly low and not realistic. For my model, total heating energy is 3154 kWh/year, of which only 97 kWh is from supplemental heat. Most federal minimum heat pumps, in our region, can only meet half of the heating load at design temperatures (if sized to meet the cooling load).

Does BEOpt not account for the decline in heating output at lower temperatures? Is there some other factor that I'm missing out on here? Thanks for any help.