Electric Tankless vs Propane Tankless
Part of our Ventilation & Hot Water guides.
Quick verdict: electric is simpler where electrical capacity allows; propane delivers more hot water in cold climates and off-grid.
Side-by-side
| Electric Tankless | Propane Tankless | |
|---|---|---|
| Venting | None | Required (indoor models) |
| Electrical | Large 240 V circuits | Minimal |
| Cold-climate output | Drops sharply | Strong |
| Off-grid | Rarely practical | Common choice |
| Fuel | Grid electricity | Propane deliveries/tanks |
Rule of thumb
Small homes in warm climates with strong electrical service: electric is simple. Cabins, RVs, cold climates or limited service: propane.
Electrical demand explained
Electric tankless heaters need a lot of current: roughly 4.2 amps per kW at 240 V. An 18 kW unit draws around 75 A, a 27 kW unit over 110 A and a 36 kW unit around 150 A, usually split over two to four double-pole breakers. Many homes with 100 A service simply can't add that load. Propane units need only a small amount of electricity for controls and ignition.
Cold climates
In northern states, incoming water can fall near 40°F in winter. Raising it to 105°F for a shower is a 65°F rise. Electric units lose flow quickly at that rise; a propane unit rated 100,000-120,000 BTU has far more heating power and keeps up with more fixtures.
Installation requirements
- Electric: heavy-gauge wire, breakers, possibly a service upgrade; no venting.
- Propane indoor: gas line sized for the BTU rating, proper venting to outdoors, combustion air, CO detector.
- Propane outdoor: no indoor venting, but freeze protection and weather exposure to consider.
Running costs
Compare your local price per kWh with your propane price per gallon. A gallon of propane contains about 91,500 BTU; a kWh is 3,412 BTU. Electric heaters are nearly 100% efficient at the point of use; propane units lose some heat up the vent. Plug your local prices into these numbers before deciding.
Our take
City homes with ample electrical capacity and mild groundwater: electric is clean and simple. Cabins, RVs, cold climates and homes with small panels: propane.
Frequently asked questions
Is propane tankless safe indoors?
When vented correctly and paired with CO detectors; follow the manual and local code.
Which is cheaper to install?
Electric is cheaper if your panel has capacity; propane needs gas lines and venting.
Can propane heaters run during power outages?
Many need electricity for ignition and controls; some have battery backups.
Is electric tankless good for cold climates?
It works but needs larger units and big electrical service.
Do propane heaters need maintenance?
Yes, annual descaling and periodic vent and burner checks.