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Tankless water heaters give you endless hot water and cut standby energy losses, but the wrong unit means lukewarm showers or a huge install bill. The two things that matter: gas vs. electric (based on your home’s existing service) and flow rate (GPM) sized to your climate and number of bathrooms.
Here are the three I’d install, covering most homes. A quick note: tankless installs often need gas-line or electrical upgrades and proper venting — budget for a pro install on gas units.
Best Gas (Overall): Rinnai RU199iN Condensing Tankless
For most homes on natural gas, the RU199iN is the one. It’s a condensing unit (~0.96 UEF, so low operating cost) with up to 11 GPM — enough for a 3–4 bathroom home even in colder climates where incoming water is cold. Rinnai is the most widely installed tankless brand, so any plumber can service it.
Best Value Gas: Rheem RTGH-95DVLN Condensing
The Rheem RTGH delivers about 95% condensing efficiency and around 9.5 GPM with a long warranty, at a friendlier price than the Rinnai. For the typical 2–3 bathroom home, it’s the best balance of cost and performance — the right pick for most gas buyers.
Best Electric: EcoSmart ECO 27 Electric Tankless
For all-electric homes, the ECO 27 is the benchmark. Its 27 kW self-modulates (it only draws the power the current demand needs) and it’s compact enough to mount almost anywhere. Note: 27 kW needs serious electrical capacity, so check your panel — but in warmer climates it delivers whole-home hot water.
How to Choose the Right Tankless Water Heater
- Decide gas vs. electric based on your existing service — switching fuel types is expensive.
- Add up your peak simultaneous hot-water flow (e.g., two showers plus a sink is roughly 5–6 GPM).
- Factor your climate: colder incoming water needs a higher-GPM unit to hit the same output temperature. Cold climates favor 9–11 GPM gas units.
- For gas, confirm your gas line and venting can support the unit (condensing units use cheaper PVC venting); for electric, confirm panel capacity.
- Have gas units professionally installed — improper venting or gas sizing is dangerous and voids warranties.
FAQ
Gas or electric tankless water heater?
Go with whatever fuel your home already uses — converting is costly. Gas units deliver higher flow rates for whole-home use in any climate but need proper venting and gas sizing. Electric units are simpler to install and great for warm climates or smaller homes, but high-output models demand significant electrical panel capacity.
What size tankless water heater do I need?
Add up the GPM of fixtures you’d run at once (a shower is about 2–2.5 GPM, a sink about 1 GPM) and match a unit that exceeds that at your climate’s temperature rise. Cold climates need higher GPM because incoming water is colder. Most 2–3 bath homes want a 9–11 GPM gas unit.
Are tankless water heaters worth it?
For most homes, yes — endless hot water, lower standby energy loss, a smaller footprint, and a longer lifespan (often 20 years vs. 10–12 for a tank). The trade-off is a higher upfront cost and sometimes gas or electric upgrades at install. Over the unit’s life, the energy savings and longevity usually pay off.
Bottom Line
For gas homes, the Rinnai RU199iN is the do-it-right choice, with the Rheem RTGH-95DVLN as the value pick for most families. All-electric in a warm climate? The EcoSmart ECO 27. Size to your peak flow and climate, match your existing fuel, and have gas units installed by a pro.