Tankless Water Heaters in Washington, IL

Are Tankless Water Heaters Worth It in Illinois?

Tankless water heaters are worth it when your household wants a supply that does not run out, and you can meet the gas, venting and sizing requirements. They are not always worth it on cost alone.

The U.S. Department of Energy's Energy Saver page says demand-type heaters can be 24 to 34 percent more efficient than storage tanks for homes that use 41 gallons or less of hot water a day. Efficiency savings on the gas bill must also cover the extra install cost, and that can take years.

How Do Tankless Water Heaters Handle Illinois Winters?

They work, but the numbers shift. A tankless unit is rated by how many gallons per minute it can heat at a given temperature rise. Supply water runs through cold ground, so in January it enters the house much colder than in July. The unit has to add more heat, and the flow it delivers drops.

For a house in Washington, where the cold season runs about December 1 to March 1 (Weather Spark), size to winter, not to summer. A unit that handles two showers in August may struggle with one and a dishwasher in January. Ask for the flow rate at a winter temperature rise, not the headline number.

How Do You Size a Tankless Water Heater?

Add up the fixtures that can run at the same time. ENERGY STAR lists these average flow rates:

Two showers and a dishwasher together draw 6.3 gallons per minute. If your unit cannot heat that much in January, one fixture goes lukewarm when another opens. Then you choose: a larger unit, two smaller units, or habits that stagger use. Count the real overlap in your house, not the possible one.

What Does a Tankless Install Include?

Plan on gas and venting work on top of the unit itself. ENERGY STAR tells installers to determine whether the existing natural gas line is sufficient, and to identify how the combustion gases will be vented. A tankless burner draws far more gas at full fire than a tank burner, so an old half-inch run may be too small. We size the pipe from the meter to the unit and finish with a gas pressure test and leak check. The meter itself belongs to the utility.

• Venting. The unit needs a sealed path to the outdoors, through a wall or the roof. Old tank flues are rarely right for a tankless unit.
• Power. Most gas units need an outlet nearby for the fan and controls. That means no hot water in an outage.
• Condensate. High-efficiency models drip acidic condensate that needs a drain, such as a floor drain or a pump.
• Service valves. They let the unit be flushed without cutting pipe.

If you smell gas near any appliance, leave the house, then call Ameren Illinois or 911 from outside.

How a Tankless Installation Goes

The order matters, because gas and vent decisions come before the unit is chosen.

1. Count the overlap. We list the fixtures that run together and work out flow at a winter temperature rise.
2. Walk the route. Gas pipe from the meter, vent path, outlet and condensate drain.
3. Quote each part. Unit, gas, vent and drain work appear as separate lines.
4. Mount and pipe. The unit goes on the wall, with water lines and service valves.
5. Run gas and vent. Gas work gets a pressure test and leak check before the burner fires.
6. Fire it and measure. We confirm temperature at the tap and show you the flush routine.

What Rules Apply to a Tankless Install?

ENERGY STAR notes a local permit may be required. In Washington, permits last six months, contractors register with the city, and the city's inspection line is (309) 444-1122, weekdays 8:00 AM to 5:00 PM. Confirm with the city, or the village hall if you live elsewhere.

This job touches three trades' rules. Water piping falls under the Illinois Plumbing License Law, 225 ILCS 320, so ask for the number and check the IDPH lookup. Gas piping needs a pressure test and leak check, and Ameren Illinois handles its meter. Any new circuit is electrical work, so ask who does it.

Does a Tankless Water Heater Need Flushing?

Yes, and it matters more with hard water. Minerals form scale inside the heat exchanger, the narrow passages that carry water past the burner. Scale restricts flow, hurts efficiency and trips error codes. A flush circulates a descaling solution through the unit using the service valves, then rinses it clean.

How often depends on your water hardness, which varies by supply, and a test settles it. Follow the manufacturer's manual. A water softener helps protect a tankless unit if your water is hard.

What Goes Wrong With Tankless Heaters?

Most problems trace to scale, gas supply or airflow.

• Error codes and shutdowns. Scale, a dirty flame sensor, a blocked vent or condensate drain are common causes.
• Lukewarm water. The unit is undersized for the flow, or scale limits heat transfer.
• No ignition. Low gas supply, a closed valve or a failed igniter.

Repair is possible on a sound unit. We start with a flush and a vent and gas check before replacing parts. Our water heater repair page covers tank units in the same detail.

What Does a Tankless Installation Cost?

A Today's Homeowner estimate of $772 to $1,931 covers water heater installation in general. It is not specific to tankless and it is not our quote. Gas pipe sizing, venting and condensate drain work are the usual reasons a tankless job costs more than a tank swap.

These are the things that move a tankless quote most:

• Unit size. A winter-sized unit costs more than one sized for July.
• Gas pipe. A long or undersized run from the meter adds the most.
• Vent route. A short wall exit is simpler than a long roof run.
• Condensate and power. A drain or a new outlet adds labor.

Ameren Illinois lists a $50 rebate on a new ENERGY STAR gas tankless water heater, one per household, bought by December 31 and claimed within 60 days (as of 2026). Confirm before you buy. The federal 25C and 25D credits expired on December 31, 2025.

When Is a Tank the Better Choice?

A tank wins if your gas line and vent would need a lot of work, if your budget is tight, or if your use is light. It also wins if outages are a concern, since many tanks with pilot lights keep heating without power. For those cases, read about water heater installation for tanks.

Tankless wins for larger households that want continuous hot water, homes with space for a wall-mounted unit and an easy vent route, and owners who will flush it on schedule. Our water heaters overview explains how to decide between repair and replacement first.