About HeatPumpMath
A heating cost calculator that shows its working, states its assumptions, and publishes its mistakes.
The problem this site was built for
Almost every heat pump calculator on the internet tells you that you will save money. Most of them reach that conclusion by using a single national average fuel price, and many make a second error that is harder to spot.
The U.S. Energy Information Administration publishes residential natural gas prices monthly. That figure is total revenue divided by total volume. In summer, residential gas volume falls close to zero while the fixed monthly customer charge stays where it is, so the apparent price per thousand cubic feet roughly doubles. A calculator that pulls the most recent EIA month is therefore answering a winter question with a summer number.
The first version of this site had that same bug. Fixing it changed the answer in most of the country. Georgia's gas price fell from $3.21 per therm to $1.50, an overstatement of 114%. Under a cold climate heat pump against a 95% AFUE furnace, the number of states where the heat pump costs less to run fell from 19 to 4. That correction is written up in full in the corrections log.
What this site does
It answers one question: for your state, your current fuel, and your equipment, does a heat pump cost less to run? It uses the heating season mean of EIA state level prices, the same months for every state, and it names those months on every page.
Where the two options land within 10% of each other, it says so instead of declaring a winner. Fuel prices move more than 10% between seasons, so a narrower margin than that is noise.
What this site does not do
It does not model purchase price, installation, rebates, financing, emissions, or comfort. It also ignores the fact that a heat pump does the work of an air conditioner in summer, which changes the capital comparison considerably. A system that costs more to run can still be the better purchase once all of that is counted.
It is also not a recommendation. If you heat with natural gas in a state with expensive electricity, this site will tell you a heat pump costs more to run, and that is simply what the arithmetic says. If you heat with propane, heating oil, or electric baseboard, it will usually tell you the opposite.
Who writes it
Ashutosh Banerjee, who goes by Ash. He holds a B.Tech in Mechanical Engineering from Sardar Vallabhbhai National Institute of Technology, Surat, awarded in 2024 with a CGPA of 9.19. He built this site after looking for a heat pump running cost calculator that would show its assumptions, and finding that none of them did.
The thermodynamics on this site is undergraduate mechanical engineering. Coefficient of performance, seasonal efficiency, and the energy content of fuels are standard material. What is unusual here is that the assumptions are written down where you can check them, and the errors are published when they are found.
Ash is based in India and writes about the U.S. residential heating market from public data. He has not installed a heat pump in a Vermont winter, and this site does not claim lived experience it does not have. What it offers instead is a model you can audit line by line, sourced to figures you can pull yourself.
How this site is paid for
At the time of writing it carries no advertising and no affiliate links, and it earns nothing. If that changes it will be disclosed on this page and in the editorial standards before any money changes hands. No advertiser will ever see a verdict before it is published, and no verdict will ever be changed to suit one.
Getting in touch
Corrections are welcome and are the fastest way to improve this site. If a number here is wrong, write to banerjeeashutosh01@gmail.com and it will be checked. Confirmed errors are logged publicly with the old and new figures.