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Tankless Hot Water Heaters: Do they work?


Water HeaterA tankless water heater is a compact unit that mounts on a wall on the inside (and sometimes outside) of the house and supplies an endless supply of hot water on demand! These water heaters save energy (and money) because they heat water as it is needed. Standard water heaters heat and re-heat water 24 hours a day.

How a Tankless Water Heater Works

Once a hot water faucet is turned on, cold water enters the tankless system. The burners ignite and the cold water is heated in the heat exchanger. The hot water then flows to the faucet or appliance. When the faucet or appliance is turned off, the tankless water heater goes into standby mode. It works on demand by using sensors and a computer board, to detect the demand for hot water in the home and adjust the rate of firing, supplying just the right amount. This way, they burn less gas if you are only running one faucet at a time. You are only burning the exact amount of fuel needed, which means savings!

Types of Tankless Hot Water Heaters

Tankless water heaters are available in electric, natural gas, and propane-fired models. Electric tankless water heaters, although still better than a standard (tank) water heater, rarely have the capacity to serve multiple fixtures (faucets and appliances) with a single unit. For this reason, most builders do not use electric tankless water heaters.

Tankless Water Heater Performance

Are tankless water heaters instantaneous?

No, not exactly. Some homeowners misunderstand "on demand" to mean "instantaneous". It takes a tankless hot water heater about 2 seconds to go from "standby" to producing hot water at the requested temperature. If that is disappointing, we recommend yoga and meditation :).

The time it actually takes hot water to reach the faucet, "lag time", depends on the size of the home and length of pipe between point A and B. In larger homes with low-flow fixtures installed is could take up to 3 minutes to deliver hot water if the fixture is far from the water heater.

Does a tankless water heater save space?

Yes! A standard tank heater installed in garage requires a floor stand, a pipe or other object to protect against vehicle impact (and usually venting all the way to the roof). In two-story homes, they require more framing. A tankless water heater is wall-mounted and can be vented through a side wall and it doesn't take up any garage floor space. Some tankless water heaters are placed in a central crawl space, near the mater bath or near the kitchen to cut down on lag time.

Sometimes, a tankless will even be installed in the attic to save space. Since there's no tank that could burst, it's not as risky as installing a tank in the attic. Tank heaters usually have an emergency drain pan, but a three-inch deep pan doesn't do much if the bottom of a 50+ gallon tank bursts!

Do tankless water heaters save energy or money?

Yes! Tankless water heaters save energy, thus money, because they do not have to keep a supply of hot water ready to go. The majority of the time, a tankless is "off". A tank heater constantly fires on and off to keep the water in its tank ready for use. Another reason tankless water heaters are energy-efficient is that they are "fully modulating". A tankless ONLY uses the fuel needed to heat water *needed at that time* to the set point. Car metaphors often work well for us: when you want to go faster in your car, you give it more gas. A tankless water heater will use less fuel if you are washing your hands versus filling up the tub. It's actually common for homeowners to see up to a 50% reduction in fuel use when switching to a tankless water heater.

Does a tankless water heater really supply _endless_ hot water?

Yup! No more shower schedules or scalding your loved one when you flush the toilet. A standard bathtub holds 35 gallons, but more popular tubs these days can hold 45 gallons or even up to 80! A tank heater would may not even fill that up, and if it did, there would be some recovery time before anyone else could use hot water. If you have chosen the right capacity for your home (max flow rank) a tankless water heater could fill up all of your tubs, then handle back to back showers, the dishwasher, and the laundry. Disclaimer: we would not actually recommend this level of irresponsible water use, and honestly, it's unrealistic. Your pipes can't even carry that much water. Point none diminished, you can call the tankless hot water supply...endless!

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