You run out of hot water halfway through the third shower, and that bulky tank in the corner still swallows energy dollars all day long. A tankless unit fixes both problems at once.
Rinnai Tankless — Top Pick
For reliable, high-flow hot water that serves a whole house even in cold climates, the Rinnai Tankless is our top pick. It's a gas unit, so budget for professional venting and gas-line installation.
In a hurry? That's our pick. Want the reasoning and the full comparison? Keep reading.
A tankless water heater heats water only when you turn on the tap, so you get an endless stream instead of a 40-gallon reserve that runs dry. No more cold surprises when the kids shower back to back, and no more paying to keep water hot at 3 a.m. when everyone's asleep. You also win back the floor space that a hulking tank used to hog.
The catch is that these units come in gas and electric flavors, and picking the wrong size means weak flow or a cold trickle in winter. This guide walks you through flow rate, temperature rise, venting, and electrical needs, then gives you four honest picks. You'll know exactly which one fits your home and your climate before you spend a dime.
Key Takeaways
- Tankless heaters deliver endless hot water and cut standby energy loss, so your bills usually drop.
- Size by flow rate (GPM) and temperature rise for your climate, not by the number of bathrooms alone.
- Gas units handle whole-house demand best; electric units skip venting and suit smaller or gas-free homes.
- The Rinnai Tankless is our top pick for reliable, high-flow whole-home hot water.
- Gas models and 240V electric models almost always need a licensed installer for venting and wiring.
Gas vs Electric: Which Tankless Heater Fits Your Home?
Gas tankless heaters burn natural gas or propane and pump out serious heat, which lets them run several hot-water fixtures at once. That makes them the go-to for whole-house duty in colder regions where incoming water starts icy. The trade-off is venting: a gas unit needs a proper exhaust path, and that adds to your install cost and complexity.
Electric tankless heaters skip the flame and the vent entirely. You mount one on a wall, run the water lines, and wire it to your panel. They shine in warmer climates, smaller homes, and any place without a gas line. The limit is your electrical service, since a whole-house electric model can pull big amperage and may need a panel upgrade.
Here's the honest read: if you have gas, cold winters, and a busy household, lean gas. If you want simple installation, no venting, and your climate is mild, electric wins. Whatever you choose, remember that gas units and 240V electric units almost always need a licensed installer to handle venting, gas lines, or heavy wiring safely and to code.
Sizing by Flow Rate and Temperature Rise
Two numbers decide whether a tankless heater keeps up: flow rate and temperature rise. Flow rate is measured in gallons per minute (GPM), and you add up the fixtures you want running together. A shower uses about 2 to 2.5 GPM, a kitchen faucet roughly 1.5 GPM, so two showers at once means you need a unit that can push around 5 GPM.
Temperature rise is the gap between your incoming water temperature and the roughly 105 to 120 degrees you want at the tap. In Florida, incoming water might already sit near 70 degrees, so the heater barely works. In Minnesota, winter groundwater can drop to 40 degrees, forcing a much bigger rise, and every unit produces fewer GPM the harder it has to heat. That's why the same heater feels powerful down south and weak up north.
You'll also choose between whole-house and point-of-use. A whole-house unit feeds your entire home from one spot. A point-of-use unit sits right next to a single fixture, like a remote bathroom or a workshop sink, delivering instant hot water without the wait. Many homes run a whole-house unit and add a small point-of-use heater for that one far-flung faucet.
Install Costs, Venting, and Electrical Requirements
Budget for more than the sticker price. A gas tankless install often runs higher because you may need new venting, a larger gas line, and a condensate drain for high-efficiency models. Electric installs cost less on venting since there is none, but a whole-house electric unit can demand two or three double-pole breakers and thick copper wiring, which sometimes means a service upgrade.
Do not treat this as a casual weekend DIY. Gas connections and combustion venting carry real safety stakes, and 240V wiring at high amperage is no place to guess. A licensed plumber or electrician sizes everything correctly, pulls permits, and makes sure your warranty stays valid. Pay once for a clean install and you'll enjoy decades of endless hot water without a second thought.
The upside pays you back. Because a tankless heater only fires when you need it, you stop wasting energy keeping a tank hot around the clock. Many households see a noticeable drop in their water-heating bills, and the units routinely last longer than tank models, so the math tends to favor going tankless over the long haul.
Quick Comparison
| Product | Fuel | Best For | Flow | Venting |
|---|---|---|---|---|
| Rinnai Tankless | Gas | Whole home | High GPM | Required |
| EcoSmart ECO 27 | Electric | No-gas homes | Modulating | None |
| Rheem Tankless | Gas/Electric | Value buyers | Solid | Varies |
| Stiebel Tempra | Electric | Precise temp | Modulating | None |
1. Rinnai — Best Overall
Rinnai Tankless
The Rinnai Tankless earns our top spot because it does the hardest job well: keeping hot water flowing to a whole house even when the incoming water runs cold. Its high GPM output means two showers and a running dishwasher won't leave anyone shivering. Rinnai's reputation for reliability is well earned, and parts and service are easy to find across the country.
You'll need a gas line and proper venting, so plan on a licensed installer. Once it's in, though, it mostly fades into the background and just works. If you want the closest thing to a set-and-forget whole-home solution, this is the unit to beat. Check current price before you buy, since gas models fluctuate.
Pros
- Strong high-GPM flow handles whole-house demand
- Trusted brand with wide service and parts support
- Performs well even with cold incoming water
- Long lifespan compared to tank heaters
- Lowers standby energy loss and bills
Cons
- Requires gas line and venting
- Higher upfront and install cost
- Professional installation is a must
2. EcoSmart — Best Electric
EcoSmart ECO 27
The EcoSmart ECO 27 is the pick for homes with no gas line or anyone who wants to dodge venting altogether. Its self-modulating technology adjusts power to match your flow, so it delivers steady temperatures without wasting energy heating water you didn't ask for. The compact wall-mount design frees up floor space that a tank used to eat.
It's a whole-house electric unit, which means it needs serious amperage and heavy wiring, so a licensed electrician should handle the hookup and may flag a panel upgrade. In warmer climates where the temperature rise is small, this heater keeps several fixtures happy. Check current price, since electric models are often the more budget-friendly entry point.
Pros
- No venting needed, simple wall mount
- Self-modulating for steady temps and efficiency
- Compact design reclaims floor space
- Great fit for gas-free homes
- Often lower upfront cost than gas
Cons
- Needs high amperage, possible panel upgrade
- Flow drops in very cold climates
- 240V wiring requires a licensed electrician
3. Rheem — Best Value
Rheem Tankless
The Rheem Tankless line is where value shoppers should look first. Rheem offers both gas and electric models across a wide price range, so you can match your fuel type and budget without overpaying. Performance is dependable, the brand is everywhere, and finding a technician who knows Rheem is never a problem.
Because the lineup is so broad, read the specs on the exact model you're eyeing: some are point-of-use, others whole-house, and venting needs change accordingly. Whether you go gas or 240V electric, plan on professional installation. For most homeowners chasing a strong balance of price and performance, Rheem hits the sweet spot. Check current price to compare models.
Pros
- Wide range of gas and electric models
- Strong value across price points
- Widely available service and parts
- Options for whole-house or point-of-use
- Dependable, no-drama performance
Cons
- Specs vary a lot between models
- Higher-flow models still need pro install
- Venting requirements differ by unit
4. Stiebel — Best Premium Electric
Stiebel Eltron Tempra
The Stiebel Eltron Tempra is the premium electric choice for people who care about precise, steady water temperature. German engineering shows up in its smart modulation, which holds your set temperature even as flow changes, so you get no annoying swings between warm and scalding. It's sleek, quiet, and built to last.
You pay more for that precision, and like any whole-house electric unit it demands heavy wiring that a licensed electrician should install. If you want the most refined electric experience and your climate cooperates, the Tempra delivers. Check current price and confirm your panel can support it before you commit.
Pros
- Precise, stable temperature control
- Advanced self-modulation for comfort
- No venting, clean wall-mount design
- Quiet operation and solid build quality
- Energy-efficient on-demand heating
Cons
- Premium price versus other electric units
- Needs heavy amperage and pro wiring
- Flow limited in very cold climates
Which Should You Choose?
Best for cold climates and big households
If you live somewhere with icy winter groundwater and a house full of people showering at once, go gas and go whole-house. The Rinnai Tankless is built for exactly this, pushing high GPM even when the temperature rise is steep. Pair it with a licensed installer for the venting and gas line, and you'll never fight over hot water again.
Best for homes without a gas line
No gas hookup? An electric unit skips venting and installs on a wall. The EcoSmart ECO 27 covers whole-house needs in mild climates on a friendlier budget, while the Stiebel Tempra brings premium temperature precision if you'll pay for it. Confirm your electrical panel can handle the load first, then bring in an electrician.
Best for tight budgets and mixed needs
When price matters most, the Rheem Tankless line lets you choose gas or electric and dial in the exact flow you need. Match a whole-house unit to your main demand, or add a point-of-use model for a far bathroom. It's the flexible, wallet-friendly path to endless hot water.
Ready to reclaim endless hot water?
Pick the unit that matches your fuel, climate, and household, then have a licensed pro handle the install. Check the current price on our top pick and take back control of your hot water for good.
Explore Brainstamped's Free ToolsFrequently Asked Questions
Usually, yes. Because a tankless unit only heats water when you open a tap, it cuts the standby energy loss a tank suffers keeping 40 gallons hot all day. Most homes see a meaningful drop in water-heating costs, and the units tend to outlast tank models, which helps the long-term math.
Size by flow rate and temperature rise. Add up the GPM of fixtures you'll run at once, then check your incoming water temperature. Colder climates need a higher temperature rise, which lowers a unit's usable GPM, so a home in Minnesota needs more heater than the same home in Florida.
Gas units deliver higher flow and handle cold-climate whole-house demand best, but they need venting. Electric units skip venting and suit warmer climates, smaller homes, or any place without a gas line. Your fuel access, climate, and electrical panel capacity decide the winner.
It's not recommended. Gas models require combustion venting and gas-line work, and 240V electric models pull heavy amperage that demands proper wiring. A licensed plumber or electrician handles permits, safety, and code, and keeps your warranty intact. Pay once for a clean install.
A whole-house unit feeds your entire home from one location. A point-of-use unit sits right beside a single fixture for instant hot water with no wait. Many homes run a whole-house heater and add a small point-of-use unit for a distant bathroom or workshop sink.