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Electric vs Gas Tankless
Quick answer: Gas tankless usually delivers more whole-home flow (about 5–9 GPM) and suits cold climates, but needs venting and gas capacity. Electric is cheaper where the panel allows, needs no vent, and fits warm climates or point-of-use; whole-home units can need 100–150 amps. Example: gas $3k–$5.5k; electric $1.5k–$4.5k.
Context: same goal, different limits
Both types heat water on demand. Gas units burn natural gas or propane and are limited by burner size and gas supply. Electric units use resistance elements and are limited by your electrical service. The right choice depends mainly on your climate, existing fuel, electrical panel capacity and local energy prices.
Terms
- kW: electric power rating; 1 kW ≈ 3,412 BTU/h.
- Amps: current drawn; a 27 kW unit at 240 V draws about 112 A.
- BTU/h: gas input rating; see BTU explained.
- Venting: required for gas units; not for electric.
Side-by-side comparison
| Factor | Gas tankless | Electric tankless |
|---|---|---|
| Whole-home flow (example) | 5–9 GPM | 3–6 GPM (warm climate) |
| Cold-climate performance | Strong | Limited by kW |
| Venting | Required | None |
| Fuel upgrade risk | Gas line upsizing | Panel / service upgrade |
| Unit price (example) | $800–$2,500 | $500–$1,500 |
| Installed total (example) | $3,000–$5,500 | $1,500–$4,500+ |
| Efficiency | ~0.80–0.97 | ~0.98–0.99 at the unit |
| Maintenance | Descaling, combustion checks | Descaling, element checks |
Process: choosing
- Check your climate and winter inlet temperature (see cold climate).
2. Total peak flow with the GPM calculator.
3. For electric, estimate amps with the electric amps calculator.
4. For gas, estimate input with the BTU calculator.
5. Ask a licensed electrician or gas fitter to confirm capacity.
6. Compare running costs with local rates in the cost savings calculator.
Worked example
Figures below are illustrative examples (2026-10-29), not quotes or guarantees.
Assumptions: 4 GPM peak, 60°F rise (warm-ish climate).
- Electric: kW ≈ GPM × rise ÷ 6.83 ≈ 4 × 60 ÷ 6.83 ≈ 35 kW, about 146 A at 240 V. Many 200 A homes cannot add that without an upgrade. Example installed: $2,000 unit + install, plus $1,500–$3,000 if a service upgrade is needed.
- Gas: 4 × 60 × 500 ÷ 0.95 ≈ 126,000 BTU/h — well within a standard 160,000–199,000 BTU/h unit. Example installed $3,500 including venting.
- Running cost (example): heating 15,000 gallons/yr at a 60°F rise ≈ 7.5 million BTU. Electric at $0.15/kWh ≈ $330/yr; gas at $1.20/therm and 0.95 efficiency ≈ $95/yr. Your rates change the answer.
When electric makes sense
- Warm climates with modest peak demand.
- Point-of-use at a single sink or bathroom — see point-of-use tankless.
- Homes without gas service and with spare panel capacity.
When gas makes sense
- Cold climates or high simultaneous use.
- Homes with existing gas service near the heater location.
- Where gas is cheaper per unit of energy.
FAQ
Is electric safer?
It has no combustion or venting, but high-amperage circuits must be installed by a licensed electrician.
Can I switch from gas to electric?
Possibly, if the panel allows. A licensed electrician checks service size.
Which is greener?
It depends on your grid's power sources versus gas combustion; both avoid standby loss.
What about propane?
Similar to gas performance with different fuel prices. See propane tankless.
Safety and code reminders
Gas, venting, combustion air, condensate disposal and high-amperage electrical work all carry real safety risks, including carbon monoxide, fire, scalding and shock. They are also governed by local code and permits that differ between towns and provinces or states. Treat every step on this page as preparation for a professional visit, not as instructions to do the work yourself. Keep the manufacturer's manual for your exact model, set water temperature with scald risk in mind (120°F is a common household target), and stop and call a licensed professional whenever something is unclear.
Quick reference: typical fixture flow rates
These example flow rates help you translate everyday use into the GPM numbers used throughout this site. Check the rating stamped on your own fixtures, as older fixtures often run higher.
| Fixture | Example hot-water flow |
|---|---|
| Low-flow showerhead | 1.5–1.8 GPM |
| Standard showerhead | 2.0–2.5 GPM |
| Bathroom faucet | 0.5–1.2 GPM |
| Kitchen faucet | 1.0–1.8 GPM |
| Dishwasher | 0.8–1.5 GPM |
| Washing machine (warm) | 1.0–2.0 GPM |
| Bathtub fill | 2.0–4.0 GPM |
Add only the fixtures that genuinely run at the same time. Running the dishwasher or laundry outside shower hours is the simplest way to stay within a unit's capacity.
Questions to ask a licensed installer
Bring these questions to every quote so you can compare them fairly. Good installers welcome them, and the answers often reveal hidden costs before work starts.
- What peak GPM and temperature rise did you size this unit for, and what inlet water temperature did you assume for winter?
- Is my existing gas line, meter or electrical panel large enough, and if not, what exactly needs upgrading and what does that line item cost?
- What venting route will you use, how long is it, and does it meet the manufacturer's instructions and local code?
- Does the quote include a permit, isolation (service) valves for future flushing, a condensate drain if needed, and removal of the old heater?
- What are the labour warranty and the manufacturer's heat-exchanger and parts warranty terms, and do they require registration or yearly professional service?
- How long will the install take, and will there be a period without hot water?
How to read the numbers on this site
Every figure on TanklessMath is a planning estimate. Ranges reflect typical North American examples as of 2026-10-29 and will differ with your region, home, fuel prices and installer. Equipment ratings vary by model, so always check the specification sheet for the exact unit you are considering. When our example and a licensed installer disagree, trust the installer who has seen your home.
Next steps
Write down your peak fixtures, coldest incoming water temperature, fuel type and possible locations, then ask at least two licensed installers to confirm sizing, venting, gas or electrical capacity, permits and local code. Compare written quotes line by line so the unit, labour, materials and upgrades are separated. Questions about this site: hello@charlandandco.com.
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