Q: Am I missing the boat by not swapping my storage water heater for the tankless (on demand) type? I’m willing to make the investment but first I need to be convinced: do tankless water heaters really deliver on their promise of saving energy?
A: Thanks for your question—lots of homeowners are curious about tankless water heaters. First, let’s make sure we’re on the same page.
A storage water heater uses natural gas or electricity to keep a tank full of water simmering in your utility closet. Hot water sits in the tank, all warmed up with nowhere to go, until someone turns on a faucet. The heating element of a storage water heater comes on occasionally when the water in the tank gets below a certain temperature. Continually re-heating the water to keep it at a specific temperature uses a small but steady amount of energy.
In contrast, a tankless water heater warms the water only after a hot water tap is turned on. Very little energy is wasted because no hot water is sitting in the tank demanding infusions of energy to maintain a specific temperature. When water is heated just when it’s needed, a tankless water heater can use less energy.
A tankless water heater will save energy if you don’t use a lot of hot water in your home:
· Your household is small (one or two people).
· People in your house bathe only once every day or two.
· You don’t run the dishwasher or washing machine every day.
· Everyone is gone most of the day and perhaps for extended periods of time, such as a retired couple that leaves home to travel for days or weeks at a time.
But energy savings with a tankless water heater are far from guaranteed! Your energy savings diminish when you have more people in the house. As the demand for hot water increases, the powerful flame or electric element that heats your water in a flash switches on repeatedly. And every time it switches on, it gulps energy.
In a busy household, a tankless water heater may consume more energy than a storage water heater! So before you invest, really consider how the people in your home use hot water. And consider these tips to improve the energy efficiency of your storage water heater.
Before making the switch, also consider the expense of buying and installing a tankless water heater. They typically cost at least twice as much as storage water heaters. And it is essential that a tankless water heater be installed correctly—often at sizable expense—in accordance with the manufacturer’s instructions and applicable local building codes.
If the appliance technicians in your neighborhood won’t take the job of installing your new tankless water heater, find out why before attempting to do it yourself. They probably know some things you didn’t know (until now):
· You’ll need to upgrade your electrical or gas system when retrofitting an existing home with a tankless water heater. These systems generally require a larger gas supply line or higher voltage electrical supply because they require a lot of energy when they’re operating.
· Proper venting is essential if you’re installing a natural gas or propane model. The exhaust is very hot and full of combustion byproducts like carbon monoxide, a toxic gas. Because tankless water heaters ignite big squirts of fuel to heat water very quickly, they produce more carbon monoxide than the gas heating element of a storage hot water tank. Carbon monoxide could build up in your home if your tankless water heater is not properly vented so these gases are removed.
Related links:
Energy Savers: Tankless Water Heaters
Whole-Home Gas Tankless Water Heaters
Melinda Thiessen Spencer is a technical writer with the Washington State University Extension Energy Program. She would like to thank Jack Zeiger, a mechanical engineer at the WSU Extension Energy Program, for his help with this post.