Best Tankless Water Heaters

The EcoSmart ECO 27 is a 27 kW, 240V electric tankless heater that EcoSmart rates at a 113-amp draw on three dedicated 40A double-pole breakers, with digital temperature control in 1-degree steps from 80°F to 140°F. In a video review, TeslaMan, who installed one himself, found it kept a full house in hot water, but he had to upgrade his electrical service and replaced the heating elements three times in two years.

The Takagi T-H3-DV-N is Bob Vila's best condensing gas pick: a 10 GPM, 199,000 BTU unit built around a commercial-grade copper-alloy heat exchanger that suits heavier residential use like recirculation or space heating. It's Ultra-Low NOx compliant, which matters in strict-emission states, and Bob Vila praised that it 'provides plenty of heating power for most households.' Its 0.93 UEF trails the Rinnai RU199iN slightly and it lacks the Rinnai's smart-app polish. As a rugged, high-capacity condensing gas heater, it's an excellent whole-home choice.

The Stiebel Eltron Tempra 36 Plus is a 36 kW whole-house electric tankless heater with Advanced Flow Control, which Stiebel Eltron says slightly reduces flow when demand exceeds what the heater can handle so the temperature holds. In a video review after 10 months, Foray Fog found it cut his water-heating cost and gave his family of five unlimited hot water, but at about 3 GPM a bath plus a shower left the shower at a drizzle.

The Rinnai SENSEI RU199iN is an indoor natural-gas condensing tankless heater that Rinnai rates at 15,000 to 199,000 BTU, up to 11 GPM and a 0.95 Uniform Energy Factor. Rinnai lists it as recirculation capable, Wi-Fi capable and ENERGY STAR certified. No independent hands-on review of this exact model was found, so it is shown without a rating. It needs gas service and venting.