Heat Pump vs Gas Water Heater: Lifetime Cost Compared

What does $498.76 mean?

It means that over 13 years, heating 50 gallons of water a day with a gas storage-tank heater costs $498.76 less than heating it with a heat-pump one — $5,286.61 against $5,785.37, install, energy and maintenance all counted. The heat pump costs $1,600 more to install but saves only $84.71 a year, so thirteen years of saving add up to $1,101.24 — still $498.76 short of the install gap. The heat itself is 9.89 MMBtu a year, and the gas heater needs 159.57 therms to deliver it against 966.52 kWh for the heat pump — the heat pump is far more efficient per unit of heat, but the install gap is too wide for the saving to close it inside 13 years.

Three things to check before you trust the number

The credit flips the verdict. Tick the $2,000 federal 25C credit box and the heat-pump install drops from $2,800 to $800 — the install gap turns into a $400 advantage the other way, and the heat pump wins by $1,501.24, breaking even in year 1. The credit is modelled as a branch only, not in the headline, because it ended for systems placed in service after December 31, 2025 — it shows what the math looked like for a 2025 install, and a system installed in 2026 gets no federal credit.

The inlet and set temperatures are typical averages. 55 °F inlet and a 120 °F set point are typical US averages — colder inlet water or a hotter set point raises both bills. If your cold water arrives at 40 °F in winter, the heat needed rises by more than a fifth, and both annual costs rise with it. The gap between the two heaters grows too, because the dearer fuel carries more of the extra load.

UEF ratings are lab figures, and a heat pump cools its room. The ratings are measured under standard test conditions, and real heat-pump efficiency (COP) falls in cold spaces — a heat pump in an unheated garage in January will not hit UEF 3.0. The heat pump also cools and dehumidifies the room it sits in, which is a bonus in a warm laundry room and a penalty in a cold one. If your heater lives somewhere cold, the real saving will be smaller than the lab figure promises.

Worked example

On the defaults: 50 gallons a day; gas $1.50 a therm, EF 0.62, install $1,200, maintenance $75 a year; electricity $0.16 a kWh, heat-pump UEF 3.0, install $2,800, maintenance $75 a year; 13 years.

1. Find the heat needed: 50 × 8.34 × 65 × 365 is 9,893,325 BTU a year, or 9.89 MMBtu.
2. Find the gas energy: 9,893,325 / 0.62 / 100,000 is 159.57 therms a year.
3. Find the gas cost: 159.57 × $1.50 is $239.35 a year.
4. Find the heat-pump energy: 9,893,325 / 3.0 / 3,412 is 966.52 kWh a year.
5. Find the heat-pump cost: 966.52 × $0.16 is $154.64 a year.
6. Find the saving: $239.35 − $154.64 is $84.71 a year.
7. Find the break-even year: thirteen years of $84.71 is $1,101.24, short of the $1,600 install gap — so the heat pump never breaks even within the lifespan.
8. Find the 13-year totals: $1,200 + 13 × $239.35 + 13 × $75 is $5,286.61 for gas, and $2,800 + 13 × $154.64 + 13 × $75 is $5,785.37 for the heat pump.
9. Find the winner: $5,785.37 − $5,286.61 is $498.76 — gas wins.
10. With the $2,000 credit (2025 installs only): the heat-pump install drops to $800, its 13-year total drops to $3,785.37, and the heat pump wins by $1,501.24.

Year by year: cumulative cost

Every branch, checked

• 50 gal/day, headline defaults: 50 gal/day, headline defaults: Gas $239.35/yr vs heat pump $154.64/yr, heat pump saves $84.71/yr; gas wins by $498.76 over 13 years (never breaks even within the lifespan). 50 gallons a day, headline defaults — gas wins by $498.76 over 13 years, and the heat pump never breaks even inside the lifespan.
• 80 gal/day: 80 gal/day: Gas $382.97/yr vs heat pump $247.43/yr, heat pump saves $135.54/yr; heat pump wins by $161.99 over 13 years (break-even year 12). 80 gallons a day — a bigger household uses more hot water, so the saving grows with it: the heat pump wins by $161.99, breaking even in year 12.
• Gas $2.00/therm: Gas $2.00/therm: Gas $319.14/yr vs heat pump $154.64/yr, heat pump saves $164.50/yr; heat pump wins by $538.45 over 13 years (break-even year 10). Gas at $2.00 a therm — dearer gas widens the heat-pump saving to $164.50 a year, and the heat pump wins by $538.45, breaking even in year 10.
• Electricity $0.10/kWh: Electricity $0.10/kWh: Gas $239.35/yr vs heat pump $96.65/yr, heat pump saves $142.70/yr; heat pump wins by $255.13 over 13 years (break-even year 12). Electricity at $0.10 a kWh — cheap electricity makes the heat pump cheap to run: it wins by $255.13, breaking even in year 12.
• Gas EF 0.55: Gas EF 0.55: Gas $269.82/yr vs heat pump $154.64/yr, heat pump saves $115.17/yr; gas wins by $102.73 over 13 years (never breaks even within the lifespan). Gas EF 0.55 — a less efficient gas heater burns more gas, so the heat-pump saving rises to $115.17 a year — but gas still wins by $102.73 over 13 years.
• Heat-pump UEF 3.5: Heat-pump UEF 3.5: Gas $239.35/yr vs heat pump $132.55/yr, heat pump saves $106.80/yr; gas wins by $211.56 over 13 years (never breaks even within the lifespan). Heat-pump UEF 3.5 — a more efficient heat pump costs $132.55 a year to run, yet gas still wins by $211.56: the $1,600 install gap is too wide for 13 years of saving.
• With the $2,000 federal credit, 2025 installs only (install $800): With the $2,000 federal credit, 2025 installs only (install $800): Gas $239.35/yr vs heat pump $154.64/yr, heat pump saves $84.71/yr; heat pump wins by $1,501.24 over 13 years (break-even year 1). With the $2,000 federal credit, for systems placed in service by Dec 31, 2025 — the heat-pump install drops to $800, and the heat pump wins by $1,501.24, breaking even in year 1. The credit flips the verdict for a 2025 install.
• 20-year lifespan: 20-year lifespan: Gas $239.35/yr vs heat pump $154.64/yr, heat pump saves $84.71/yr; heat pump wins by $94.22 over 20 years (break-even year 19). 20-year lifespan — seven more years of saving tip the balance: the heat pump wins by $94.22, breaking even in year 19.
• Gas maintenance $150/yr: Gas maintenance $150/yr: Gas $239.35/yr vs heat pump $154.64/yr, heat pump saves $159.71/yr; heat pump wins by $476.24 over 13 years (break-even year 11). Gas maintenance $150 a year — dearer gas maintenance hands the heat pump $75 a year more saving, and it wins by $476.24, breaking even in year 11.
• 30 gal/day: 30 gal/day: Gas $143.61/yr vs heat pump $92.79/yr, heat pump saves $50.83/yr; gas wins by $939.25 over 13 years (never breaks even within the lifespan). 30 gallons a day — a small household saves less in absolute dollars, and gas wins by $939.25 over 13 years.

The reverses, worked backwards

• Minimum UEF (0.1 steps) for break-even within 13 years: 4.0 — at 4.0 the figures are Gas $239.35/yr vs heat pump $115.98/yr, heat pump saves $123.37/yr; heat pump wins by $3.84 over 13 years (break-even year 13); at the lower neighbor the figures are Gas $239.35/yr vs heat pump $118.96/yr, heat pump saves $120.40/yr; gas wins by $34.83 over 13 years (never breaks even within the lifespan); at the upper neighbor the figures are Gas $239.35/yr vs heat pump $113.15/yr, heat pump saves $126.20/yr; heat pump wins by $40.61 over 13 years (break-even year 13) — verdict: STEP.
• Largest electricity price (1¢ steps) for break-even in year 13 or sooner: 0.12 — at 0.12 the figures are Gas $239.35/yr vs heat pump $115.98/yr, heat pump saves $123.37/yr; heat pump wins by $3.84 over 13 years (break-even year 13); at the lower neighbor the figures are Gas $239.35/yr vs heat pump $106.32/yr, heat pump saves $133.04/yr; heat pump wins by $129.48 over 13 years (break-even year 13); at the upper neighbor the figures are Gas $239.35/yr vs heat pump $125.65/yr, heat pump saves $113.71/yr; gas wins by $121.81 over 13 years (never breaks even within the lifespan) — verdict: STEP.
• Largest gas price (1¢ steps) for gas to still win over 13 years: 1.74 — at 1.74 the figures are Gas $277.65/yr vs heat pump $154.64/yr, heat pump saves $123.01/yr; gas wins by $0.90 over 13 years (never breaks even within the lifespan); at the lower neighbor the figures are Gas $276.06/yr vs heat pump $154.64/yr, heat pump saves $121.41/yr; gas wins by $21.64 over 13 years (never breaks even within the lifespan); at the upper neighbor the figures are Gas $279.25/yr vs heat pump $154.64/yr, heat pump saves $124.60/yr; heat pump wins by $19.85 over 13 years (break-even year 13) — verdict: STEP.
• Largest heat-pump install ($100 steps) for the heat pump to win over 13 years: 2300 — at 2300 the figures are Gas $239.35/yr vs heat pump $154.64/yr, heat pump saves $84.71/yr; heat pump wins by $1.24 over 13 years (break-even year 13); at the lower neighbor the figures are Gas $239.35/yr vs heat pump $154.64/yr, heat pump saves $84.71/yr; heat pump wins by $101.24 over 13 years (break-even year 12); at the upper neighbor the figures are Gas $239.35/yr vs heat pump $154.64/yr, heat pump saves $84.71/yr; gas wins by $98.76 over 13 years (never breaks even within the lifespan) — verdict: STEP.
• Smallest whole gal/day for the heat pump to win over 13 years: 73 — at 73 the figures are Gas $349.46/yr vs heat pump $225.78/yr, heat pump saves $123.68/yr; heat pump wins by $7.82 over 13 years (break-even year 13); at the lower neighbor the figures are Gas $344.67/yr vs heat pump $222.69/yr, heat pump saves $121.98/yr; gas wins by $14.21 over 13 years (never breaks even within the lifespan); at the upper neighbor the figures are Gas $354.24/yr vs heat pump $228.87/yr, heat pump saves $125.37/yr; heat pump wins by $29.84 over 13 years (break-even year 13) — verdict: STEP.
• Smallest whole lifespan for the heat pump to win: 19 — at 19 the figures are Gas $239.35/yr vs heat pump $154.64/yr, heat pump saves $84.71/yr; heat pump wins by $9.51 over 19 years (break-even year 19); at the lower neighbor the figures are Gas $239.35/yr vs heat pump $154.64/yr, heat pump saves $84.71/yr; gas wins by $75.20 over 18 years (never breaks even within the lifespan); at the upper neighbor the figures are Gas $239.35/yr vs heat pump $154.64/yr, heat pump saves $84.71/yr; heat pump wins by $94.22 over 20 years (break-even year 19) — verdict: STEP.

What the defaults assume

The defaults are 50 gallons of hot water a day, a $1,200 gas heater at EF 0.62 against a $2,800 heat-pump heater at UEF 3.0, $1.50 a therm, $0.16 a kWh, and a 13-year lifespan. They are a starting point, not a quote: your household may use more or less water, your fuel prices will differ, and the right answer for you is the one your numbers describe. The 55 °F inlet and 120 °F set point are typical US averages — colder inlet water or a hotter set point raises both bills. Standby losses are inside the EF and UEF ratings, no rebates are modelled in the headline, and tankless systems are a different comparison — see the tank-vs-tankless-water-heater guide. Put your numbers in, read the answer, and check the working before you use it.

These notes repeat in every explainer section because this page is built to be read start to finish: the 2025 credit flips the verdict; the inlet and set temperatures are typical averages; and UEF ratings are lab figures, and a heat pump cools its room.

Output · formula · meaning

Who uses this

• A homeowner replacing a dead water heater — $1,600 more to install, $84.71 a year back, never breaking even in 13 years without the credit, $1,501.24 ahead with the 2025 credit.
• A homeowner with both fuels available weighing a gas line against a heat pump — the install gap and the (2025-only) credit are the two numbers that decide it.
• A landlord fitting out a rental — the year-by-year table shows exactly when the dearer heater starts paying for itself.
• A buyer comparing quotes — two install prices, an EF and a UEF and two fuel prices, and the lifetime gap follows from them.

Accuracy & limitations

The arithmetic is exact on the numbers you type: 50 gallons a day at a 65 °F rise is 9,893,325 BTU a year, and 159.57 therms at $1.50 is $239.35. What the calculator cannot do is measure your home: UEF/EF ratings are lab figures; real HPWH efficiency (COP) falls in cold spaces; the heat pump also cools and dehumidifies its room; rebates vary by state and utility and are not modelled in the headline. The federal 25C credit of up to $2,000 ended for systems placed in service after December 31, 2025, so a system installed in 2026 gets no federal credit — the credit branch shows the 2025 math only. The 55 °F inlet and 120 °F set point are typical US averages — colder inlet water or a hotter set point raises both bills. Standby losses are inside the EF and UEF ratings, and tankless systems are a different comparison. Fuel prices are held flat — if gas gets dearer or electricity gets cheaper, the gap narrows; if the reverse, it widens. Treat the answer as a comparison of two quotes, not a quote itself.

Cite this calculator

On 50 gallons a day, gas costs $239.35 a year against $154.64 for the heat pump — a saving of $84.71 a year — and over 13 years gas wins by $498.76: the heat pump never catches up within the lifespan. With the $2,000 federal credit for a 2025 install the heat pump wins by $1,501.24. Minimum UEF (0.1 steps) for break-even within 13 years: 4.0. Largest electricity price (1¢ steps) for break-even in year 13 or sooner: 0.12. Largest gas price (1¢ steps) for gas to still win over 13 years: 1.74. Largest heat-pump install ($100 steps) for the heat pump to win over 13 years: 2300. Smallest whole gal/day for the heat pump to win over 13 years: 73. Smallest whole lifespan for the heat pump to win: 19. Source: Bright Side Kit, brightoolbox.com.

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