Space heating
Replacing a gas furnace with an electric heat pump that both heats and cools.
Annual running cost, three ways
Space heating: annual energy cost
Replacing a gas furnace with an electric heat pump that both heats and cools.
| Scenario | Estimated annual cost |
|---|---|
| Today — gas furnace, about 10 years old | $323/yr |
| Electric, on PG&E E-ELEC | $204/yr |
| Electric, on your own solar | $0/yr |
Assumes an average San Francisco single-family home burning 116 therms a year on space heating, through a furnace about 10 years old: 80% AFUE on the label, delivering about 72% of that fuel energy into the living space once duct losses are taken off. The age is our assumption about a typical replacement-age system, and the derating from 80% to 72% is our engineering judgement rather than a measured figure — both are stated so they can be argued with.
E-ELEC Assumes the heat pump runs mostly off-peak. Heating load in San Francisco concentrates in the morning and overnight rather than in the 4-9pm peak window, so this is a reasonable assumption for most homes.
Solar $0 is the marginal cost of solar you generate and use yourself. It is not system payback, and it is not the export credit value of power you send back to the grid.
How we built this number
Nothing above is a headline figure we were handed. It is derived, step by step, from a stated consumption assumption and a stated efficiency, both of which are published with their sources. If you disagree with an input, you can see exactly which one to argue with.
The arithmetic
- 116 therms/yr burned
- x 29.307 kWh/therm = 3400 kWh of gas energy
- x 0.72 delivered efficiency = 2448 kWh of heat actually delivered
- / 3.7 seasonal COP = 662 kWh/yr of electricity
- Fuel used today
- 116 therms
- Cost of that fuel
- $323
- Electricity instead
- 662 kWh
- Cost on E-ELEC
- $204
- Annual difference
- $119
The consumption assumption
Assumes an average San Francisco single-family home burning 116 therms a year on space heating, through a furnace about 10 years old: 80% AFUE on the label, delivering about 72% of that fuel energy into the living space once duct losses are taken off. The age is our assumption about a typical replacement-age system, and the derating from 80% to 72% is our engineering judgement rather than a measured figure — both are stated so they can be argued with.
The rates we priced it at
Both sides of this comparison are priced at published rates, effective 2026-06-01: a PG&E residential fuel rate on the old equipment, and PG&E's E-ELEC electricity rate on the new. The exact figures, what they include, where they came from and when they were last checked are all on the methodology page. Rates move, and when they do, every number on this site moves with them.
The time-of-use caveat
E-ELEC is a time-of-use rate, not a flat price. Assumes the heat pump runs mostly off-peak. Heating load in San Francisco concentrates in the morning and overnight rather than in the 4-9pm peak window, so this is a reasonable assumption for most homes.
This matters more than most people expect. The same appliance on the same rate plan can cost substantially more or less depending purely on the hour it runs, which is why we state the assumption rather than quietly averaging it away.
Why it costs less to run
What it is like to live with
What it changes beyond the bill
What we do not cover: your electrical panel
Running cost is only half the question. The other half is whether your existing electrical service has the capacity to take the new equipment — because if it does not, a panel upgrade can cost more than the appliance that triggered it, and take considerably longer to arrange.
We do not answer that, here or in a report. This site used to promise a load calculation against your panel and it was never built; it would also need a photo of the inside of your panel, which is not on the list of things the privacy policy says we collect — and that list changes before the product does, not after.
So every upfront cost we publish assumes no electrical panel upgrade and no major duct replacement. On an older house that is the assumption most likely to be wrong, either one can add thousands, and it is the first thing worth asking a contractor about.
Now do it with your numbers
This page describes an average San Francisco home. A personal analysis rebuilds the same comparison from your postcode, the equipment you have today and how far you drive, and tells you what the change would cost upfront as well as what it would save. The form asks which upgrades you want costed, and if you came here for Space heating, that is the one to tick. We can do this across Pacific Gas & Electric territory — 1,227 of California’s 2,654 postcodes.
Generated from your answers, checked by a person before it is sent. Pay what you can, including nothing.