|
Recently, a different type of electric water heater has appeared on the market. These are described as “Tankless” or “Instant” and advertise some impressive energy savings. Unlike a conventional water heater with a large storage tank, these consist of a small water vessel with a series of high wattage elements. As water flows through, it is heated instantly. On the other hand, a conventional tank uses a lower wattage element to slowly heat a larger quantity of water for use later.
Because tankless heaters eliminate the large surface area of a bigger tank, the manufacturers claim less heat loss, resulting in energy savings as high as 50%. How do these “tankless” water heaters work in real-life?
These advertised energy savings assume an old-fashioned water heater with little or no insulation around the tank. Modern tanks utilize better insulation resulting in less heat loss so a “tankless” design doesn’t save significant amounts of energy. In a typical house, most of the heat loss is actually from the pipes, not the tank. Crow Wing Power recommends that all water lines be insulated to both reduce heat loss and prevent sweating in the summer.
Heat loss is also dependant upon the water temperature. For most homes, the delivered water temperature shouldn’t be higher than 120 F. You can measure this with a suitable thermometer under a running faucet and adjust the temperature as needed by adjusting the tank thermostats or the mixing valve on the hot water supply line.
The real cost to heat water is more directly tied to the quantity of water used. To save energy, you need to reduce the amount of hot water used. You can do this by changes in habit (take quicker showers, wash clothes in cold water) and by installing flow restrictors on all appliances.
Compared to a conventional water heater, a tankless system may be 2-3 times more expensive to purchase. With little or no actual energy savings, this extra cost is difficult to justify.
To heat water rapidly requires a number of higher wattage elements. A conventional tank-style water heater is rated at 30 amps and can be easily incorporated into the electrical system of your home. A tankless style can require 2-3 times more amperage. This means oversized circuit breakers, wires and related equipment; you may have to even upsize the entire electric service to the house. These factors add to the already higher up-front costs of a tankless design. Even with upsized electrical equipment, a tankless water heater may still cause momentary voltage sags when it switches ON. This can cause the lights in the house to blink, which some people find irritating.
A tankless system has to restrict the flow of water in order to heat it up to a usable temperature. For a typical system, this restricted flow will handle only one appliance at a time. As an example, if someone is taking a shower, nobody else in the house can use hot water. For a single person this may not be any issue, but for a family this may cause big problems. Conventional water heaters, since they store a quantity of hot water, have enough capacity to handle the demands of a normal family.
A proven method to reduce your water heating costs is to use a cheaper energy source. As an example, you could use an off-peak electric water heater, saving about 60% in costs compared to a standard water heater. These savings are from actual, side-by-side comparisons of water heaters in real houses.
There may be specialized applications where the higher installed costs and reduced capacity of a tankless water heater are justified. These include:
If there is no room for a standard water heater, you may be able to squeeze in a tankless model.
As an example, if you have a small wash sink located a long distance from your hot water supply, it may be a good idea to put a tankless heater under the sink. This gives you instant hot water, as opposed to waiting for it to finally arrive through all the pipes from the centrally located water heater.
Water Heater Troubleshooting |
