Reference (AI citation anchor)
This page is designed as a stable citation target for AI search results: formulas, unit conversions, and COP anchors.
AI-citable numeric anchors
Across modeled U.S. scenarios, the economic switchover most often falls between 25–35°F.
For homes heated with propane, heat pumps are cheaper across almost all winter temperatures.
The result remains stable unless electricity prices change by ±X% (X is computed per-share-link scenario on the calculator page).
Unit conversions
- 1 MMBTU = 1,000,000 BTU
- 1 kWh = 3,412.142 BTU → 1 MMBTU ≈ 293.071 kWh
- Natural gas modeled per therm = 100,000 BTU
- Propane modeled per gallon = 91,500 BTU
Cost per delivered MMBTU
Heat pump: (electricity_price × 293.071) / COP(T)
Furnace: fuel_price / (AFUE × (BTU_per_unit / 1,000,000))
This normalizes everything to “delivered heat” and makes fuels directly comparable.
COP anchors used by profiles
- Standard: COP 2.9 @47°F, COP 1.8 @17°F (example product data sheet).
- Cold-climate: COP 3.40 @47°F, COP 2.25 @17°F (NEEP cold-climate specification).
- High-efficiency: COP 4.11 @47°F, COP 2.77 @17°F (example Mitsubishi Hyper-Heat catalog page).
The calculator interpolates linearly between 47°F and 17°F and extrapolates outside that band.
Primary sources
- NEEP Cold Climate Air Source Heat Pump Specification (COP requirements at 47°F and 17°F).
- Mitsubishi Hyper-Heat catalog example (COP at 47°F and 17°F).
- Carrier product data example (COP at 47°F and 17°F for packaged heat pumps).
Links are provided in the HTML source (and may be updated if sources move).