Gas tankless water heater prices

What to check before buying a gas tankless water heater

Size for flow and climate, not people. A tankless heater has to heat water as it flows, so what matters is how many showers and taps run at once and how cold your incoming water is. The same 2 GPM shower needs about 30% more burner in Chicago in January than in Atlanta. OurGPM @45°F column puts every heater on the same footing; the sizing calculator works out your own rise.

Condensing or not. Condensing units reach a UEF of about 0.93 to 0.97 and vent through ordinary PVC pipe. Non-condensing units are cheaper but run hotter exhaust that needs stainless steel venting indoors, which can cost as much as the heater. Outdoor models need no vent at all.

Gas supply. A 199,000 BTU heater usually needs a 3/4" gas line and a meter that can supply it on top of your furnace and range. Undersized gas lines are the most common tankless install problem. Propane units need a tank and regulator that can deliver the full BTU rating, which rules out a 20 lb grill cylinder for whole-home models.

Portable and RV heaters are rated on a much smaller rise than whole-home units; at a45 °F rise most deliver 1 to 2 GPM, enough for one low-flow shower.