Efficient tank-type water heaters.
The weak point with tank-type water heaters (regardless of energy source) has always been standby heat loss. When the hot water stored in the tank cools, energy is required to bring water temperature back within the 120-140 degree range. This cooling and reheating cycle goes on continuously, whether hot water is being used or not. To reduce standby heat loss and make tank-type water heaters more efficient, today’s ENERGY STAR® models are equipped with extra tank insulation.
Tankless water heaters.
Also known as “demand” water heaters, these units never waste energy because of standby heat loss. Instead, the heating element is activated only when a hot water tap or washing machine is turned on. Most tankless water heaters burn natural gas or propane fuel, and are small enough (about the size of a suitcase) to be mounted on the wall, taking up very little space. Depending on water usage habits, replacing a tank-type water heater with a tankless model can cut your water-heating expenses by as much as 40%. But it’s important to note that a tankless water heater can cost twice as much to install as a new tank-type heater.
Heat pump water heaters
This tank-type water heater relies on a small, electrically powered heat pump instead of an electric resistance heating element. A heat pump water heater can be twice as efficient as standard electric tank-type water heater, making it a smart upgrade if you need to replace an old tank-type water heater.
Indirect water heaters
With an indirect water heating system, your whole-house boiler, furnace or heat pump does double duty. In addition to keeping your home warm, this HVAC equipment also heats the water you use for washing. In other words, you don’t need a separate water heater. During winter months when your HVAC system is supplying heat to the house, you get your hot water for free.
Types of Water Heaters
If you've ever had to endure a cold shower, you won't dispute the water heater's status as a major household appliance. Water heaters are described in a number of ways - by the fuel or energy source they use, by their capacity, and even by the technology they rely on. It's useful to know something about different types of water heaters because each type has its own set of pros and cons, and because sooner or later, you'll need a new model.
Tank Water Heaters
A tank-type water heater has been the standard choice for heating water for many years. The heat source can be electricity, natural gas, propane or fuel oil. With fuel-fired heaters, the heating element (or burner) is at the base of the tank, and a flue extends up the center of the tank. Some fuel-fired heaters vent up a chimney. A direct-vent or sealed combustion water heater can vent directly through an exterior wall.
Tank-type water heaters come in different sizes. A 40-gal. model can be adequate for two people. A family of four can get by with 40 or 50 gal. A larger family usually requires a 60-gal. or 80-gal. water heater.
Heat Pump Water Heaters
A heat pump water heater also qualifies as a tank-type water heater, but a small air-source heat pump provides the primary heat source. Like other heat pumps, this one uses a refrigerant to extract heat from the surrounding air and move it to a heat exchanger, where water heating takes place. Regular electric heating elements inside the tank can provide backup heating if necessary. A heat pump water heater is about twice as efficient as a standard electric water heater, but it's also more expensive. Because the heat pump will cool the surrounding space, it may not be suitable for use in cold climates where basements and utility rooms need to be kept reasonably warm.
Indirect Water Heaters
An indirect water heater utilizes heat that is supplied by a furnace, boiler or heat pump. In an immersed coil installation, the hot water tank contains a heat exchanger that is connected to a furnace, boiler or heat pump. In a tankless coil installation, the water heating coil is located in the furnace or boiler, eliminating the need for a hot water storage tank. An indirect water heater can be very efficient, but this efficiency is tied to the performance of the attached heating appliance.
Tankless Water Heaters
A tankless water heater means home energy saving simply because of how it works. Unlike a tank-style heater that consumes energy heating and re-heating water even when it's not being used, a tankless heater only heats water once, when you call for it. Retiring an old tank-type water heater and replacing it with a tankless model can cut water heating expenses by as much as 45%. Tankless water heaters that run on natural gas and propane are more efficient than electric models.
Because of their ability to modulate and match output capacity to actual hot water demand, tankless water heaters are very proficient at meeting multiple demands simultaneously. You never run out of hot water like you do with a tank-style water heater. Some tankless units can even serve two purposes, combining hot water heating with space heating.
Tankless water heaters are compact - about the size of a carry-on bag. Heaters typically mount on a wall; installation locations are flexible, since there's no need to worry about leaks or flooding. Gas-fired models need to be vented to the outside.