Instant Hot Water Saves Money and Energy

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Energy Saving Instant Hot Water

Do you leave your lights on at home all day and night? Of course not. Do you leave your cars engine running while parked at work or in the garage at home just to keep it warm? Ridiculous! Then, why is the water heater left on all day and night just to keep the water warm when no one is using it?

Water heaters with tanks constantly heat and reheat water all day and all night. Sure, adding an insulation blanket helps keep water in the tank warmer a little longer, but heated water in the pipes cools off continuously, not to mention all the natural gas and propane that is just wasted warming the flue all day and night.

How do you save money and stop wasting energy?

Replace your home water heater with one or more tankless heaters. Tankless heaters only heats water when you need it and not when you don’t.

Tankless Brands

Several Tankless brands are available. The most popular (in alphabetical order) are Bosch, Paloma, Rheem, Rinnai, Ruud, and Takagi.

Sizing a tankless heater

Plumbers recommend water heater sizes based on how much water is used and how long it takes to reheat a full tank of water after it is used. I bet you don’t have time to wait 30 minutes or more after each family member showers? Bigger needs demand water heaters with bigger tanks. As an example, a typical 40 gallon tank natural gas heater operating at 40,000 BTUs might take as long as 40 minutes to reheat a full tank of water. A typical electric heater might take a full hour to reheat a full 40 gallon tank.

Tankless hot water heaters are sized differently. They deliver instant hot water and heat water as long as you need it. A mid-sized system with a 6 gallon / min (6 GPM) flow rate delivers 360 gallons per hour continuously. Use the table below for approximate tankless heater sizing, or ask your plumber if you aren’t sure. Obviously a small unit delivering 2.2 gpm would be appropriate for a single bathroom or kitchen, but isn’t big enough to serve full house needs. Medium sized tankless water heaters deliver 6 – 6.6 gpm while large residential tankless water heaters deliver up to 8 gpm. Up to 4 residential tankless water heaters can be strung together in a centralized system to serve large homes, or can be distributed around the house to provide “instant on” hot water supply right where it is needed.

Gallons/minute (gpm)

Low flow



Restroom Faucet

0.5 – 1.5


3.0 – 5.0

Kitchen Faucet

1.5 – 2.0


3.0 – 7.0

Utility Faucet

1.5 – 2.0


3.0 – 7.0

Bathtub Spout



5.0 – 14.0

Shower Head

1.0 – 2.0


4.0 – 8.0





Clothes Washer




NOTE: Please consult your local building, plumbing and electrical codes and hire a licensed plumber to install your tankless waterheater, and a licensed electrician for an electric appliance.

write by Brian Brown

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