Tankless, sized for February.Tankless water heater installation in Cleveland, Ohio.

How tankless works

Hot water on demand.

A tankless (on-demand) water heater has no storage tank. When a hot tap opens, flow through the unit triggers a gas burner or electric elements that heat the water as it passes through a heat exchanger. No tank means no standby heat loss from keeping 40 or 50 gallons hot around the clock.^[1]

The trade-off is that output is limited by flow. A tankless unit is rated for a certain number of gallons per minute at a certain temperature rise. Ask for more than that and the water coming out gets cooler. That is why sizing is everything, and why sizing on the shore of Lake Erie is different than sizing in a warm groundwater city.

Some contractor pages talk about Cleveland "groundwater" temperatures as if the city drank from wells. Cleveland Water is explicit: its drinking water comes from Lake Erie, a surface-water source, through four intakes in the Central Basin that send water to four treatment plants.^[2] Surface water runs colder in late winter than typical groundwater. This site does not publish a measured tap-water temperature — treat the calculator slider as a what-if tool, and ask the installer to size from a winter value, not a July value.

Who tends to like tankless

• Homes with natural gas and a workable route for new venting
• Households that want to free up basement floor space
• Owners planning to stay long enough to benefit from the longer service life^[1]
• Anyone tired of the last shower going cold, as long as the unit is sized for peak flow

Who might be better off with a tank or heat pump

• Homes without gas, where whole-home electric tankless can mean major electrical upgrades^[3]
• Homes where a straight tank swap avoids venting and gas-line changes
• Households with very high simultaneous demand that would need more than one unit

Thinking about switching from a tank? The conversion page covers gas supply, venting, condensate, and electrical. Comparing types? See tank vs tankless.

What installation involves

More than hanging a box on the wall.

Gas supply

Whole-home gas tankless units fire at a much higher input than a typical gas tank. The gas piping and meter have to support the unit's maximum input along with the furnace and other appliances. Gas-line upsizing is one of the most common reasons a conversion grows in scope.^[1]

Venting

A tankless unit generally cannot reuse an old tank's draft-hood vent. Many condensing models vent with plastic pipe through a sidewall; non-condensing models need stainless or manufacturer-specified venting. Vent route, clearances to windows and doors, and snow drifting against Cleveland sidewalls all matter.

Water, condensate, and scale

Condensing units produce acidic condensate that needs a drain, often with a neutralizer. Isolation valves are commonly added so the heat exchanger can be descaled later. In water that Cleveland Water reports as 105–130 mg/L hardness, skipping those valves is how a five-year-old unit becomes a service call.^[2]

Electrical

Gas tankless units still need power for controls and fans. Electric tankless units may need very large circuits and create high peak loads.^[3]

Location

DOE guidance favors a central location to keep pipe runs short, since long runs mean waiting for hot water and wasting water.^[1]

Permits

In the City of Cleveland, new or replaced water heaters require a plumbing permit.^[5] The installer can typically handle it.

Tank vs tankless at a glance

The groundwater mix-up

Cleveland does not drink well water.

Some tankless sizing write-ups talk as if Greater Cleveland homes draw groundwater that sits near a steady temperature all year. Cleveland Water is clear on the source: Lake Erie, a surface-water source, four intakes in the Central Basin, four treatment plants, about 1.4 million customers.^[2] Underground pipes take the edge off open-lake temperatures, but they do not turn lake water into well water. Late winter is still the design case.

This site does not publish a measured incoming temperature at Cleveland taps, because Cleveland Water's quality report lists hardness and other chemistry, not an official year-round inlet temperature for tankless charts. The honest method is the one DOE already published: pick the coldest incoming water you reasonably expect, add up simultaneous fixture flow, and choose a unit rated for that flow at that rise.^[3] The sliders above are a sketch of that method, not a specification.

Whole-home vs point-of-use

A whole-home gas tankless unit is the conversion most people mean when they say they want tankless. Point-of-use electric units under a sink can solve a long pipe run or a far-away bathroom without replacing the main heater. They are a different product with a different electrical need. Mixing the two conversations is how a quote goes sideways.

Recirculation

Waiting for hot water after you open a tap is a piping problem, not a tank problem. Tankless does not shrink the pipe between the heater and a third-floor bathroom in an older Cleveland house.^[1] Recirculation loops or a pump at the fixture can cut that wait; they also use energy and, if they run constantly, they can make a tankless unit cycle more often. Ask whether a recirculation option is worth it for your layout instead of assuming it comes for free with the heater.

ENERGY STAR and incentives

ENERGY STAR certifies whole-home gas tankless models that meet its efficiency criteria.^[7] Certified models are the ones that typically show up in federal tax-credit discussions when those credits are available.^[8] This page does not list dollar amounts or claim a local utility rebate that has not been independently verified here.

What the installer should measure

• Existing gas-pipe size and approximate length, plus what other appliances share it
• A realistic vent route to a sidewall or roof, with snow and window clearances in mind
• Whether a condensate drain is nearby if the unit is condensing
• Household peak flow: showers, tubs, laundry, kitchen
• A winter incoming-water assumption, not a summer one
• Isolation valves for later descaling, given Cleveland Water's hardness range^[2]

If a quote skips those items and only names a brand, it is not a Cleveland winter quote yet. The conversion page covers the infrastructure side in more depth.

FAQ

Tankless questions.