EcoSmart ECO 36
#1 in ElectricFull review
For a large home with 300 A service that wants all electric hot water. The lifetime warranty and low price per kilowatt make it a strong value if a pro installs it.
Amazon $699$699
A tankless water heater heats water as it flows through, so it never runs out of hot water and wastes no energy keeping a tank warm. These rankings compare what the makers publish on the same terms: how much heating power you get for the money, how much power there is, how efficiently it turns fuel into hot water, and how long the heat exchanger, the part that fails, is covered.
Heating power sets how many taps a heater can run at once. A gas heater at 199,000 BTU/h can run two or three showers in a cold climate; an electric heater needs about 27 to 36 kW to do the same, and a home with a 200 A service to power it. Flow figures in gallons per minute depend on how much the water has to be warmed, so a heater rated at 9 GPM in Florida may give half that in Minnesota.
Gas heaters, on natural gas or propane, have the most power and suit most whole homes, but need a gas line big enough and a vent. Condensing models reach about 0.93 to 0.96 UEF and vent through cheap PVC. Electric heaters need no vent or gas, cost less up front and suit warm climates, small homes and single sinks.
Top Picks
Eccotemp 7GB Builder Grade
#3 in GasFull review
A strong value outdoor heater for a natural gas home in a mild climate, with a better warranty than most budget rivals.
Amazon $499$499
Rinnai Sensei RX199i
#1 in GasFull review
A top choice for a large home that wants one heater for three or more showers at once with the lowest gas bills Rinnai offers.
Amazon $1,532.79$1,532.79
Shop by Fuel
Gas
20 rankedNatural gas and propane heaters with the power for two or three showers at once.
Top rated: Rinnai Sensei RX199i $1,532.79
Electric
20 rankedCompact heaters with no venting, for warm climates, small homes and single sinks.
Top rated: EcoSmart ECO 36 $699
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Prices were last checked October 31, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Best Gas Tankless Water Heaters
- Rinnai Sensei RX199i#1 of 20Full review
A top choice for a large home that wants one heater for three or more showers at once with the lowest gas bills Rinnai offers.
Amazon $1,532.79$1,532.79199,000 BTU/h11 GPM0.98 - Rheem RTGH-95DV#2 of 20Full review
A well priced condensing whole home heater for buyers who want PVC venting and lower gas bills.
Amazon $1,411.70 Amazon $1,411.99$1,411.70199,900 BTU/h9.5 GPM0.93 - Eccotemp 7GB Builder Grade#3 of 20Full review
A strong value outdoor heater for a natural gas home in a mild climate, with a better warranty than most budget rivals.
Amazon $499$499180,000 BTU/h7 GPM- - Rheem RTG-95DV#4 of 20Full review
A whole home indoor heater for buyers who want maximum burner size without the condensate drain of a condensing unit.
Amazon $1,201.29$1,201.29199,900 BTU/h9.5 GPM0.82 - Rheem RTG-70DV#5 of 20Full review
A budget indoor heater from a major brand for a two bathroom home in a moderate climate.
Amazon $653.77 Amazon $785.13$653.77160,000 BTU/h7 GPM0.82
Best Electric Tankless Water Heaters
- EcoSmart ECO 36#1 of 20Full review
For a large home with 300 A service that wants all electric hot water. The lifetime warranty and low price per kilowatt make it a strong value if a pro installs it.
Amazon $699$69936 kW8.8 GPM0.94 - Stiebel Eltron Tempra 36 Trend#2 of 20Full review
The pick for a larger home with 300 A service that wants electric whole house hot water, even in cooler regions. Few electric heaters match its power and warranty.
Amazon $749$74936 kW7.5 GPM0.98 - Stiebel Eltron Tempra 29 Trend#3 of 20Full review
For homes with 200 A service in mild climates that want two showers at once from one heater.
Amazon $639.99$639.9928.8 kW6 GPM0.98 - Stiebel Eltron Tempra 24 Trend#4 of 20Full review
A whole home heater for a two bathroom house in a warm or mild climate with 150 A service or more. The 7 year leakage warranty is the main reason to pay over the Rheem.
Amazon $514.23$514.2324 kW5 GPM0.97 - EcoSmart ECO 11#5 of 20Full review
For a single shower or a pair of sinks in a warm climate, with a lifetime warranty if a pro installs it.
Amazon $244.78$244.7813 kW3.2 GPM0.92
How We Rank
Each heater is ranked against others of the same fuel, and scored on its price per unit of heating power, its heating power, its efficiency and its heat exchanger warranty.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per 1,000 BTU/h (gas) or per kW (electric) | 35% |
| Heating power | gas input, BTU/h; electric, kW | 25% |
| Efficiency | Uniform Energy Factor | 15% |
| Warranty | heat exchanger warranty | 25% |
How we rank explains each factor in full.