Best Propane Tankless Water Heaters (2026)

The RTGH is a condensing propane unit with a stated UEF of 0.93 and 199,900 BTU of input, rated at 9.5 GPM. Condensing means a second heat exchanger recovers heat from the exhaust, so it vents in PVC and wastes less of the fuel you pay to truck in.

The efficiency matters more on propane than on natural gas, because propane costs more per BTU. At 0.93 efficiency the useful heat is about 186,000 BTU, which is about 5.3 GPM at a 70F rise and 9.3 GPM at a 40F rise. Compared with the non-condensing Rheem RTG at 0.82, it extracts about 13 percent more heat from the same fuel.

Ownership needs a condensate drain and neutralizer, a properly sized propane line and regulator, and a yearly descale. Plan on a large tank or a bulk delivery contract, since the burner uses about 2.2 gallons of propane per hour at full fire. Ask the propane supplier to confirm that the tank, the first-stage regulator and the line to the house can deliver the full input, because a frosted regulator on a cold morning is the classic cause of a sudden loss of hot water.

This RTG is the outdoor liquid propane version, rated 7.0 GPM at 160,000 BTU and 0.82 UEF. Outdoor mounting removes the vent run entirely and keeps combustion out of the house, which is the main reason to choose it for a cabin or a retrofit with no good vent path.

The tradeoff is freeze exposure. An outdoor unit needs its freeze protection to work, which depends on electric power, and in a long outage in a cold climate the water in the heat exchanger can freeze. Against the RTGH it is less efficient and needs no condensate line, and against the indoor units it avoids venting.

Ownership is the usual descale and inlet screen care, plus a look at the cabinet and vent cap after storms. Check the regulator and the propane line for leaks each year. If you live where winter outages are common, plan a small generator or battery backup for the freeze protection, since an unpowered outdoor unit relies on you draining it.

Ranein's 190,000 BTU unit is rated at 8.5 GPM for four to six water points and places its fan underneath the combustion chamber, which the listing says prevents smoke backflow. It uses a three-quarter inch inlet.

Its rating deserves a calculation. At 190,000 BTU and a non-condensing efficiency near 0.8, the useful heat is about 152,000 BTU, giving roughly 4.3 GPM at a 70F rise and 7.6 GPM at a 40F rise. The 8.5 GPM headline therefore assumes a rise near 36F. Compared with the Rheem RTGH it has similar input but no stated UEF, and compared with the Westinghouse it has much more capacity.

Ownership includes the usual descaling, venting and regulator care. Because the brand is less established, check the warranty and parts availability before you buy. Keep an eye on the propane tank level during the first winter, because a high-input unit shows you how fast a modest tank empties.

Westinghouse's propane unit lists 120,000 BTU, 5.5 GPM, app control and an LED panel, with self-modulating technology that adjusts gas and water flow to hold the setpoint. It is aimed at whole-home use in a mid-size house.

At 120,000 BTU and an efficiency near 0.8, the useful heat is about 96,000 BTU, so roughly 2.7 GPM at a 70F rise and 4.8 GPM at a 40F rise. It suits two to three fixtures in a mild climate. Compared with the Ranein it has about two-thirds of the input, and compared with the APUS it adds app control and more input.

Ownership is routine: descaling, an inlet screen check and a venting inspection. The app is a convenience, and the physical panel is the fallback. A well-sealed vent and a combustion air path matter more on propane than people expect, since propane is heavier than air and settles low if it leaks.

The CZ422LP is the propane version of ThermoMate's small tankless, with 102,000 BTU, a rated flow up to 5 GPM, CSA certification and eight listed protections. The listing says it can run two showers at once, which is true only in a mild climate.

At 102,000 BTU the useful heat is roughly 82,000 BTU, so about 2.3 GPM at a 70F rise and 4.1 GPM at a 40F rise. In a cold climate it serves one shower at a time. Against the APUS 95,000 BTU it has slightly more input, and against the Rheem it costs less and burns less fuel.

Ownership centers on a correctly set regulator, a yearly descale and a vent check. The protections help, but they do not replace a proper installation. It is also the easiest of the six to size a tank around, because its fuel draw sits near one gallon per hour.

APUS's 95,000 BTU propane unit lists 4.42 GPM for two to three fixtures, a 95F to 140F temperature range and sensors with a smart CPU for steady output. It uses an oxygen-free copper heat exchanger.

The flow claim needs a reality check: at 95,000 BTU and about 0.8 efficiency, the useful heat is about 76,000 BTU, which is roughly 2.2 GPM at a 70F rise and 3.8 GPM at a 40F rise. It suits a small home or two fixtures in a mild climate. Compared with the ThermoMate it has slightly less input, and compared with the Westinghouse it lacks an app.

Ownership is the usual descale, screen and vent care. Its low input also lowers the propane draw, which helps if your tank is small. Pair it with a low-flow shower head if your tank is small, which stretches both the hot water and the fuel.