# HeatPumpMath

> A calculator for whether a heat pump costs less to run than an existing gas,
> propane, oil, or electric resistance heating system, computed per US state
> from EIA heating season fuel prices.

Author: Ashutosh Banerjee (Ash Banerjee), B.Tech Mechanical Engineering, SVNIT Surat.
Contact: banerjeeashutosh01@gmail.com

## What the model does
Compares cost per delivered kWh of heat. A heat pump is cheaper when
electricity $/kWh divided by fuel $/kWh-equivalent is below effective COP
divided by AFUE. Effective COP includes electric resistance backup at COP 1.0,
weighted by share of heat delivered.

## Key findings
- Against a 95% AFUE gas furnace with a HSPF2 11.0 heat pump and 10% backup
  heat, the heat pump costs less to run in 4 of 45 states, more in 33.
- Against propane, heating oil, and electric resistance, the heat pump wins in
  almost every state.
- EIA residential gas prices in summer months run up to 114% above heating
  season figures, because the published price is revenue divided by volume.

## Scope
Running cost only. Excludes equipment price, installation, rebates, financing,
emissions, and summer cooling.

## Data
Every figure is downloadable as CSV and JSON under CC BY 4.0 at
https://heatpumpmath.com/data/. Prices are the December 2025 to February 2026 EIA heating season
mean, pulled 31 August 2026. Attribution: HeatPumpMath.

## Pages
- /: calculator
- /states/: all states compared
- /data/: the figures as CSV and JSON, with the licence and the limitations
- /methodology/: equation, constants, sources, limitations
- /corrections/: published errors with old and new figures
- /notes/: long form reasoning