Is a tankless water heater worth it in Northeast Ohio?

What are the real pros and cons of a tankless water heater?

You gain hot water that does not run out, lower running cost and a longer life, and pay with a higher up front cost, a winter flow ceiling and more upkeep.

Pros

• Continuous hot water, up to a maximum flow set by heating capacity, temperature setting and incoming water temperature, per a DOE Building America selection guide.
• Almost no standby loss, the heat a tank loses and replaces while water sits in it. ENERGY STAR says standby time can be 96 percent of a tank's operating time each day.
• Lower running cost. A 2012 DOE Building America tankless guide, written before federal tank efficiency minimums rose in 2015, estimated 5 to 40 percent less a year to run than a tank on the same fuel.
• Longer life, less floor space. ENERGY STAR puts the life expectancy at 20 years, and the unit hangs on a wall.

Cons

• Higher up front cost. The tankless guide calls it significantly higher.
• A wait and a minimum flow. The selection guide says delays of 20 seconds or so are not uncommon, and flows below roughly 0.4 to 0.75 gallons per minute (gpm) may not fire the unit.
• Needs power. Without a battery backup, an outage means no hot water, and one manufacturer's manual says to drain the unit if power or gas is lost in freezing weather.
• A flow ceiling that drops in winter, and scheduled flushing, both covered below.

Tank or tankless: how do they compare side by side?

A tank costs less and stores a set amount of hot water. A tankless unit costs more, heats only as water flows, lasts longer and needs its own vent and flushing.

Is a tankless water heater worth it for a Northeast Ohio household?

It can be, with natural gas or propane, a workable vent route, showers that run back to back, and enough years in the house for the lower running cost to offset the higher installed cost. It is harder to justify in an all electric house.

Leans yes: your tank runs out, you want the longer life, or you want the floor space.

Think twice:

• Electric only. The tankless guide says whole house electric units may be cost prohibitive in cold regions, and most need 50 to 200 amps, which can mean panel work.
• Small, steady demand. Then a tank costs less to put in and does the job.
• No one will keep up the flushing. Scale restricts flow and shortens the unit's life, the tankless guide warns.

Cost depends on the gas piping, vent route, condensate drain, outlet, water line and whether the heater moves. An on site quote is the way to get a real number.

How big a tankless water heater do I need?

Size it by the most hot water the house uses at once, in gpm, and the temperature rise (how far the heater must warm the incoming water) in the coldest month, then check the manufacturer's flow chart.

1. List what runs at once. ENERGY STAR's averages: shower or tub 2.5 gpm, clothes washer 3.3, sink 2.2, dishwasher 1.3. The EPA says standard showerheads use 2.5 gpm and WaterSense labeled heads no more than 2.0.
2. Add up the realistic peak, such as two showers and the dishwasher on a school morning.
3. Find the rise: your output temperature, which the tankless guide puts at 120 F for most uses, minus your coldest incoming water temperature.
4. Read the chart. The unit must deliver your peak gpm at your rise.

How does cold winter water change the sizing?

It widens the rise, so the same unit heats less water. On the lake's average temperatures off Cleveland, it delivers a little over half its August flow in January.

In January 2021 Cleveland Water reported Lake Erie at 37 F or lower at all four intakes, and said the temperature stays about the same on the way to your house.

The National Weather Service's 1981 to 2010 averages for the lake off Cleveland are 35 F in January and 74 F in August. February averages 34 F and its coldest days 33 F, so size with a few degrees to spare. On another system, ask your utility for its winter minimum; on a well, have the installer measure it.

A worked example: flow rate x temperature rise

Two showers plus the dishwasher, heater at 120 F:

Cleveland Water's intakes draw from deeper in the lake, so August tap water may run cooler than 74 F. January sets the size.

A burner's maximum output is fixed, so a unit that just covers 6.3 gpm in August covers about 3.4 gpm in January (6.3 x 46 / 85): one shower and a trickle.

And 6.3 gpm at an 85 F rise is more than the largest household units can heat: the biggest in the Rinnai manual, at 199,000 Btu per hour, charts about 4.5 gpm at that rise. WaterSense heads cut the peak to 5.3 gpm, and since a shower is mixed to about 105 F at the head, as in the tankless guide's example, each 2.0 gpm shower draws only about 1.6 gpm from a 120 F heater: about 4.6 gpm in all, just over that limit. So stagger the dishwasher or install two units as a bank.

Will my gas line, meter and venting support a tankless unit?

The existing vent, no: a tankless unit needs its own. The gas line and meter, maybe: at up to 200,000 Btu per hour, a tankless unit can draw four to nearly six times the gas of a typical tank, so have them checked first.

• Gas piping and meter. The tankless guide says a unit may need a larger line to the meter or a dedicated line, and in most cases 3/4 inch pipe to the heater. ICC guidance on the 2009 fuel gas code sizes piping as if every appliance runs at full output at once, so its load adds to your furnace's.
• Venting. DOE's Building Science Education Solution Center says cold climates need sealed combustion (outside air in, exhaust out), direct vent or power vented units, vents above the snow line, and the intake far enough from the exhaust to prevent frost. If the old tank shared a flue with the furnace, that flue was sized for both and may not clear the furnace's exhaust on its own, so the DOE Building America Solution Center says to have the installing contractor test the furnace's draft after the tank comes off it. Ask for that test on the quote.
• Condensate and power. Condensing units, the higher efficiency kind that recover heat from the exhaust, need a condensate drain, and gas units need an outlet nearby.
• Water line. The tankless guide says units typically need a 3/4 or 1 inch supply, and an old house may have only a 1/2 inch main.

You can safely read the gas input on your water heater and furnace rating labels, where you can see them without removing a panel. Leave gas piping, gas valves and vents to a professional.

Natural gas has no smell of its own; the rotten egg or sulfur smell is an odorant added so you notice a leak. If you smell it, treat it as gas even if you think it is the floor drain. Get everyone out of the house right away, without using light switches, phones, lighters, flashlights or the garage door opener, which can spark, or touching gas valves. From a safe place, call 911 and your gas company's emergency line (for Enbridge Gas Ohio customers, 1-877-542-2630).

How often should a tankless water heater be flushed?

As often as the manual says for your water. The tankless guide puts it anywhere from twice a year to once every three years, depending on the manufacturer and use.

Flushing clears scale, the minerals that build up in the heat exchanger. Cleveland Water lists its hardness at 7 grains per gallon (120 mg/L), below the 8 to 14 grain range where the tankless guide says manufacturers may require a softener. The minerals are still there, so flush on schedule.

• Some units show a flush reminder at an interval the installer sets for your water, and a higher temperature setting speeds up scale, one manual says.
• The flush, done with the power disconnected and the water shut off, pumps white vinegar through the service valves for at least an hour. Isolation valves, which the manual strongly recommends and we install, make the hookup quick.
• The manual says a professional should do the yearly inspection and maintenance, flushing included, so call one when the reminder shows. Your part: keep the vent terminals and condensate line clear of snow and ice.

When to call Raber HVAC

If your tank is aging or you want the two compared, call (216) 888-4822 or book a visit online. We install tank and tankless water heaters with isolation valves for flushing, an expansion tank where code calls for it and a drain pan when the location warrants. The office is open every day from 8:00 AM to 10:00 PM, and the 24/7 emergency line covers active leaks, no heat and sewage backups.

Sources

• IBACOS for DOE Building America: Measure Guideline, Transitioning to a Tankless Water Heater (2012)
• ARBI (Davis Energy Group) for DOE Building America: Strategy Guideline, Proper Water Heater Selection (2015)
• DOE Building Science Education Solution Center: Tankless WHs Gas Fired
• DOE Building America Solution Center: Gas-Fired Tankless Water Heaters
• ENERGY STAR: Save More with Gas Tankless Water Heaters
• ENERGY STAR: Whole Home Tankless Gas Water Heaters
• ENERGY STAR: Technical Bulletin, Demand Water Heaters
• U.S. EPA WaterSense: Showerheads
• Cleveland Water: Lake Erie
• Cleveland Water: High Oxygen Saturation in Lake Erie Can Mean Bubbly Water at Your Tap
• Cleveland Water: FAQs
• National Weather Service Cleveland: Average Lake Erie Water Temperatures
• International Code Council: CodeNotes, Pipe Sizing Based on the 2009 IFGC and IRC
• Rinnai: N Series Residential Condensing Installation and Operation Manual
• Enbridge Gas Ohio: Report Gas Emergency