How do heat pumps affect your utility bill?

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In honor of Heat Pump week this week, I want to share how my utility use has changed as I’ve replaced gas appliances with electric.

Electricity use has gone up

This will come as a surprise to no one, but my electricity use has gone up. The graph below shows how it has changed over the last fifteen years. You can see it has gone up from about 550 kWh/month (on average) to 750 kWh, almost a 40% increase!

But there’s something interesting if you look closer. There was an increase in 2019. Then use went down through 2021. Then it went back up again. What explains that?

I got an EV in November 2018. I use 150-200 kWh of energy each month for the EV (it’s a pretty efficient Chevrolet Bolt). So that explains the jump up in 2019. (1) But what about the decrease? That is when I switched to LED lighting. I had some unusual light fixtures, but when the pandemic came around, it seemed like a fine time to do some research and swap out my bulbs. It made a big difference, essentially paying for my driving.

Then there is a jump of around 200 kWh/month in 2022. That is when I electrified my house. In November of 2021 I electrified the boiler, and in December of 2022 I electrified the water heater. So that ended up increasing my bills by about 200 kWh * $.23/kWh = $46/month or around $600/year. Not the end of the world, but not chump change either. (2)

In the monthly graph below you can see how the electric heating in particular has affected electricity use in winter.

Gas use has gone down

As expected, my gas use has dropped dramatically. You can see a gradual decrease in the first 5-6 years as I adjusted my thermostat (and eventually got a smart thermostat), and then in 2022 I electrified. The little that is left is for the gas stove. (3)

This graph of monthly use shows the gas-fired boiler (for space heating) going away first, in November 2022, and then the gas-fired water heater being removed in May 2023.

That adds up to cost savings

How has this translated bill-wise? Well, I dropped on average about 35 therms of gas each month (420 per year), and added (not including the EV) about 200 kWh per month. (4) If gas to the home costs $2/therm, and electricity to the home costs $0.23/kWh, then I have saved $70/month in gas and added $46/month in electricity. That is a win! The electricity also includes the air-conditioning that I get in summer. I don’t use it much, but it’s nice when I do.

In Palo Alto we are blessed with low electricity rates. If you live in a place with higher rates, or you live in Palo Alto and want to dig into the details of how heat pumps might affect your bills, check out a blog post I wrote a few years ago on how to answer common questions about utility use and bills from heat pump specs. For those in PG&E territory, PG&E provides a calculator here, but I’m not sure how recent it is.

Total energy use has gone down

One thing that’s really interesting to note from this is the relative efficiency of the heaters. The amount of energy in one therm is equivalent to 29.3 kWh. So the 35 therms I dropped are “worth” about 1025 kWh. But I only added 200 kWh. How can that be? What that means is that my electric heating is five times (!) as efficient as my gas heating.

My boiler was not very wasteful (it was about 95% efficient), but the water heater was not great (about 65% efficient). That is not uncommon for a gas tank water heater, wasting 33% of its energy. In contrast, the electric heating generates 3-4 times more energy than it consumes! (5) So it’s something like 300-400% efficient.

Overall, my electric appliances are about five times more efficient than my gas appliances, and that is why electric heating can cost less even if electricity is more expensive than gas on a per-unit-of-energy basis.

Caveat: My bills have still gone up

The electric heating has helped me to save about $600/year. But nevertheless my bills have gone up. The graph below shows what my electricity and gas bills (combined) were for each year, minus approximate EV use. Despite overall use going down, my bills have gone up because rates have gone up. In 2010, electricity rates were about half what they are now, and I expect gas was similar. (6) Fortunately the switch to heat pumps has saved me about 25% on my combined bill ($600 out of about $2400).

Palo Altans can find more information about home electrification here. The Switch Is On also provides great resources.

I’d love to hear about your experience with home electrification, energy use, utility bills, etc.

Notes

1. I don’t have a graph showing the decrease in gasoline use, which has gone to zero. And I don’t have a graph showing the bills. But with our Tier 2 electricity rate at $.23/kWh, and gas at around $6/gallon (!), right now I am saving about $10 for every 100 miles I drive. The Chevrolet Bolt gets around 4 miles per kWh, and each kWh costs $.23. So that is around $5.75 per 100 miles. In contrast, assume an efficient gas or hybrid car gets 40 miles per gallon, and each gallon costs $6. That is $15 per 100 miles. Even with “normal” gas prices, I save around $5 per 100 miles.

2. This is for a 1955 home with a twenty-year-old foam roof that’s been recoated, and dual pane windows with some wall insulation. The new electric heating is efficient electric heat, with a Chiltrix CX-34 air-to-water heat pump replacing the gas boiler, and an 80-gallon Ruud HPWH replacing the gas water heater.

3. My gas stove is a “rangetop”, a style that wraps around the front of the counter. There are not many induction rangetop models, especially that are reasonably priced, so I am waiting until there are more. For now, I pay much more for the monthly fixed charge of the gas than I do for the 1 therm or so that I use each month.

4. The amount of energy in one therm is equivalent to 29.3 kWh. So the 35 therms I dropped are “worth” about 1025 kWh. But I only added about 200 kWh. That shows that my electric heating is five times (!) as efficient as my gas heating. My boiler wasn’t bad (about 95% efficient), but the water heater was not great (about 65% efficient). This is in contrast to the electric heating which generates 3-4 times as much energy as it consumes. This “five times more efficient” thing is why electric heating can cost less even if electricity is more expensive than gas on a per-unit-of-energy basis.

5. It sounds like it must violate some fundamental law of thermodynamics for an appliance to generate more energy (in heat) than it consumes. But what these heat pumps do is they steal the heat (energy) from the air around them (which gets cooler). They do use some electrical energy (kWh) — to power a refrigerant cycle and to operate a fan — but the (heat) energy they send into your house is captured from the surrounding air. So they’re really moving heat, not generating it, which is how they use so little energy.

6. If you are curious, a two-fold increase over 15 years represents about a 5% rate increase every year. I don’t have the exact figures for gas and electricity rate increases, but my guess is it’s closer to 1.8x (a 4% increase). Inflation was about 50% (1.5x) in that period.

Current Climate Data

Global impacts (March 2026), US impacts (March 2026), CO2 metric, Climate dashboard

March 2026 was the warmest March in the contiguous United States in 132 years of record-keeping, at 9.4°F above the 20th-century average. The January–March period was also the driest on record, breaking the previous record set in 1910. Globally, March 2026 was tied for second-warmest ever. See the above links for more information.

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