Water heating is one of the largest household energy expenses, so fuel choice matters. Gas and electric water heaters can both deliver reliable hot water, but their monthly cost depends on utility prices, tank losses, and usage habits.
This guide compares practical operating cost, not just nameplate specs. For full-home load and backup planning, use the WattSizing Calculator.
Quick Comparison
| Topic | Gas Water Heater | Electric Water Heater |
|---|---|---|
| Energy source | Natural gas / propane | Grid electricity |
| Typical operating cost driver | Fuel rate per therm or per gallon propane | Electricity rate per kWh |
| Recovery characteristics | Often faster (especially higher BTU burners) | Can be slower depending on element size |
| Backup-power compatibility | Usually low electrical demand, but fuel required | High electrical load if resistance tank type |
| Emissions and grid context | Varies by gas source and leakage assumptions | Varies by local grid mix / renewable share |
How to Compare Costs Fairly
Hot water demand is the same service, regardless of fuel. To compare fairly:
- Estimate daily hot-water energy need.
- Account for heater efficiency and standby losses.
- Apply local utility rates.
Two homes with identical water use can see different winners depending on local gas and electric prices.
Related baseline:
Cost Comparison Table (Example Rates)
Assumptions for illustration:
- Daily delivered hot-water energy need: 10 kWh thermal/day
- Electric tank effective efficiency for this example: about 0.92
- Gas tank effective efficiency for this example: about 0.65
- Electricity rate: $0.16/kWh
- Natural gas rate: $1.40/therm (1 therm about 29.3 kWh equivalent)
| Metric | Electric Tank (Example) | Gas Tank (Example) |
|---|---|---|
| Input energy/day | 10 / 0.92 = 10.87 kWh | 10 / 0.65 = 15.38 kWh-equivalent |
| Input in billing units | 10.87 kWh | 15.38 / 29.3 = 0.525 therm |
| Daily energy cost | 10.87 x $0.16 = $1.74 | 0.525 x $1.40 = $0.74 |
| Estimated monthly cost (30 days) | $52.20 | $22.20 |
With these assumptions, gas is cheaper to operate. If electricity is low-cost (or time-shifted) and gas is expensive, the difference can narrow or reverse.
Worked Scenarios
1) Family Home, Moderate Use
Assume:
- Electric water heater consumption: 13 kWh/day
- Gas water heater equivalent billing: 0.62 therm/day
Cost:
- Electric: 13 x $0.16 = $2.08/day -> $62.40/month
- Gas: 0.62 x $1.40 = $0.87/day -> $26.04/month
Difference: about $36/month in this rate environment.
2) Low-Use Apartment
Assume smaller demand:
- Electric: 6 kWh/day
- Gas: 0.30 therm/day
Cost:
- Electric: 6 x $0.16 = $0.96/day -> $28.80/month
- Gas: 0.30 x $1.40 = $0.42/day -> $12.60/month
Absolute savings are smaller at lower usage, even if percentage difference remains.
Practical Decision Factors Beyond Fuel Price
- Installed cost and venting: Gas often needs venting and fuel line constraints.
- Safety and maintenance: Both need regular maintenance; gas adds combustion/vent checks.
- Backup strategy: Electric tanks are difficult for small generators/batteries due to high element watts.
- Upgrade path: Heat pump water heaters can significantly lower electric water-heating kWh in many climates.
Related planning articles:
FAQs
Is gas always cheaper than electric for water heating?
No. It depends on local rates, heater type, and efficiency. In many regions gas is cheaper per delivered hot-water unit, but not everywhere.
Why does electric still make sense in some homes?
Simplicity, no combustion venting, and compatibility with cleaner grids or rooftop solar can make electric attractive despite higher per-kWh rates.
Do tank losses matter a lot?
Yes. Standby losses occur all day and can materially affect monthly bills, especially in low-use households.
What about heat pump water heaters?
They are electric but often much more efficient than resistance tanks, which can change cost comparisons significantly.
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Want a personalized estimate using your own rates and hot-water usage pattern? Use the WattSizing Calculator to compare operating cost and backup system sizing before you choose.
