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Gas vs electric tankless water heater: both deliver on-demand hot water, but the right choice depends on your climate, your fuel supply and your electrical panel.
Choose gas or propane if you have a gas supply, live in a cold or mixed climate, or need hot water for more than one shower at a time. Choose electric if you don’t have gas, live in a warm climate, have plenty of electrical capacity, or only need hot water for one or two fixtures.
Comparing electric vs gas tankless water heater options, or an electric tankless water heater vs gas tankless water heater, comes down to flow and installation. Are tankless water heaters electric or gas? Both exist.
| Gas / propane tankless | Electric tankless | |
|---|---|---|
| Typical whole-house output | 120,000–199,000 BTU | 18–36 kW (61,000–123,000 BTU) |
| Flow at 70°F rise | About 3–5.4 GPM | About 1.7–3.5 GPM |
| Unit price | $800–$2,500 | $500–$1,200 (whole house) |
| Venting | Required (or outdoor model) | None |
| Power needed | 120V outlet for controls | 240V, 60–150 amps |
| Efficiency | 0.80–0.97 UEF | About 0.98–0.99 UEF |
| Running cost | Usually lower with natural gas | Depends on electricity rates |
| Works in power outage | No | No |
| Maintenance | Descale, check burner and vent | Descale, check elements |
The main limit for electric tankless water heaters is power. A 36 kW unit, the largest common residential model, produces about 123,000 BTU per hour. A 199,000 BTU gas unit produces about 60% more heat. In Florida, where incoming water is warm, a 36 kW electric unit can run two showers. In Minnesota in January, it may struggle with one. Run your numbers in the sizing calculator.
Gas units need a properly sized gas line, venting through a wall or roof (or an outdoor unit), a condensate drain on condensing models and a 120V outlet. Electric units skip all of that but need heavy-gauge wiring and large breakers. Many older homes need a panel upgrade. See installation requirements and the installation cost guide.
Electric tankless units turn almost all the electricity they use into hot water. Gas units lose some heat up the vent. But electricity usually costs more per unit of heat than natural gas, so gas often costs less per month. Propane prices vary widely and can make propane units more expensive to run than natural gas.
If you are replacing a gas tank with an electric tankless unit, check two things first: whether your panel can support 100–150 amps of extra load, and whether an electric unit delivers enough flow in winter for your household. If not, a gas tankless unit or a heat pump water heater may be a better fit.
Browse electric units by kW and amperage, or switch to gas and propane models by BTU.
Both. Tankless water heaters are made in natural gas, propane (LP) and electric versions. Gas models use a burner and need venting; electric models use heating elements and need a large electrical circuit.
In most U.S. markets, natural gas costs less per unit of heat than electricity, so gas tankless units are often cheaper to run even though electric units are more efficient at the point of use. Compare your local rates.
Both can last 20 years or more with maintenance. Electric units have fewer components but elements can scale up; gas units have more parts but replaceable components. Water quality and descaling matter more than fuel.
Yes, if your electrical service can handle it. A whole-house electric unit may need 100–150 amps, which often requires a 200-amp or larger panel. An electrician should do a load calculation first.
This guide is general information for U.S. homeowners, not professional advice. Gas, electrical and venting work must follow the manufacturer’s instructions and local codes, and in most areas requires a licensed plumber, electrician or gas fitter and a permit. Specifications and prices change; always confirm details on the product page and in the installation manual.
