If you live in a home without gas lines, chances are your water is heated by electricity. These electric water heaters may seem complex, but they are fairly basic. To help better understand them, it is important to know their components.
Electric Water Heater – Tank
The tank is the most visible part of the unit. It is a long cylinder that is usually a couple feet high, 20 to 25 inches in diameter, and can hold anywhere from 40 to 80 gallons, or 151 to 303 liters, of water at a time, depending on the size of the residence.
While the exterior of the tank is metallic, the interior of the tank is composed of glass. This is because glass does not corrode when in contact with water. In between the glass interior and metallic exterior is a layer of insulation for efficiency purposes. If living in a warmer climate, this insulation is usually enough for an electric water heater and no insulation on the exterior needs to be purchased.
Electric Water Heater – Cold Inlet/Cold Water In
Water is brought from the mainline and into the unit through this supply line. It enters the unit from the top and is usually marked by word or a blue color.
Electric Water Heater – Dip Tube
Cold water from the supply line is then fed into a dip tube. This long plastic tube delivers the cold water to the bottom of the unit to utilize heat-rising properties.
Electric Water Heater – Heating Elements
Unlike gas water heaters that use natural gas lit by a pilot light, electric water heaters use burners that work in a similar manner to electric stove tops. Unlike stove tops, the burners are long and tube-like, not round. They are also designed for use in water.
While some electric water heaters have one heating element, many have two heating elements: one to heat water at the top of the tank, and another to heat water at the bottom of the tank. These two heating elements work together to efficiently heat water.
Electric Water Heater – Thermostat
Just like the thermostat on your air conditioner or heater, this thermostat is what regulates the water temperature and shuts the unit on and off. Water temperature can be manually set to conserve energy or to make water extra-hot. Standard hot water temperatures are usually between 120 to 180 degrees Fahrenheit, or 49 to 82 degrees Celsius.
If your electric water heater has two heating elements, it also has two thermostats, one connected to each burner on the upper and lower part of the unit. Typically, the upper thermostat switches on first and heats the water, with the lower thermostat activating if and when needed. Regulations deem that both thermostats be covered to protect them.
Electric Water Heater – Anode Rod
Also called the magnesium, aluminum, or sacrificial rod, the purpose of this small pole on the inside of the unit is to prevent corrosion. The pole is made of stainless steel and coated in magnesium, aluminum, or zinc in older models.
How long it lasts depends on factors such as water hardness and other chemicals present in your tap water. Other factors include the size of the unit, how much hot water is used, what temperature the unit is set at, and how many burners/thermostats it has. The average life span for a typical anode rod can be anywhere from 5 to 10 years. It should be changed when there is 6 inches or more of exposed wire at either end or if a third of the diameter has been eroded.
Electric Water Heater – Hot Outlet/Hot Water Out
This supply line carries the hot water out of the unit and throughout the home. It is also located at the top of the unit and marked by either a word or a red color.
Other Electric Water Heater Components
High Limit Switch
This safety device is used to keep water from getting too hot. It is usually located by the upper thermostat and shuts the unit off when water temperature gets too high, much like a circuit breaker will flip a switch when too much power is used.
When the high limit switch is activated and the unit is powered down. This button will turn the unit back on. It is usually red and located next to the high limit switch. Be sure and wait for the unit to cool down before hitting the reset button. If you are constantly using the button, there could be a problem with the unit.
Shut Off Valve
One of three valves located on electric water heaters, this one is used to keep cold water from entering the unit. The valve is located on the cold water supply line and knob shaped.
This valve is used to drain water from the electric water heater. When using this valve, be sure and place a container for the draining water. The drain valve is located on the bottom of the unit and shaped like a sink faucet with a nob on top.
Temperature/Pressure Relief Valve/ T&P Valve
When the electric water heater gets too hot, the increased temperature will cause increased pressure. This valve is used to release this pressure. It works in a similar manner to the cap located on the top of a radiator in a vehicle. Use caution when turning this knob located on the top of the unit as hot gas can be released.
Under normal conditions the T&P valve will not cycle. It will only open if the thermostat(s) fail and the unit over-heats the water, threatening the integrity of the tank. The T&P opens to vent water and pressure to prevent catastrophic failure. The life expectancy of the T&P is about 6 to 8 years. If the T&P drips at the basement sump or exterior drain line, then it needs to be replaced. A replacement T&P valve generally costs only around $20, and is well worth the price. Please check the T&P drain at least twice a year.
This pipe is connected to the temperature/pressure relief valve, and its function is to take excess water out of the unit. A good tip is to place a pan below the pipe to determine if any excess water is being produced by the unit.
Unlike gas heaters that must be connected to gas lines, electric heaters can be installed anywhere that carries an outlet capable of its electricity usage, proximity to water lines, and indoors. For safety purposes, electric water heaters should never be exposed to outdoor elements.
Electric Heater vs. Gas Heater
If you have the option to choose either a gas or an electric heater, there are a few differences to consider. These water heaters have similar components and functions, the main difference being gas heaters use a flame, pilot light, and burner to heat water. There is also usually just one heating element in a gas heater.
When it comes to efficiency, gas heaters can be more economical in that they produce hot water more efficiently with a power supply that is usually cheaper than traditional electricity. However, gas water heaters are usually more expensive and may not be worth the extra cost if your home does not use a lot of hot water.
Tank vs. Tankless
Like the above, there are pro’s and con’s to each. Traditional electric water heaters constantly heat the water in the tank whether it be a 40 or 80 gallon one which can lead to higher bills. Tankless units heat water as needed which save on electricity bills. However, much like gas heaters, tankless heaters are more expensive than traditional ones, and it’s a good idea to calculate your hot water usage to see if the extra cost is worth it.
Other Important Facts About Electric Water Heaters
- Water heaters are the second highest source of energy usage in the home. (Air conditioning/Heating is the first).
- Electric water heaters are usually 4500 watts no matter what their size.
- Tankless residential water heaters usually come in voltages from 120 to 240 but are also available in other voltage capacities.
- Energy Star is the sign of an efficient water heater, and heaters with this label use 14 to 55 percent less energy than non-certified units. They also rate gas water heaters and solar water heaters.
- Energy Star electric water heaters are commonly referred to as heat pump water heaters or HPWH’s. These heaters often employ technology similar to a heat pump home heating system.
- Unlike home heating or cooling systems, electric water heaters are low maintenance, with the upkeep of the anode rod being the best thing for the unit.
- The average life span for electric water heaters is 10 to 15 years, with typical warranties from 6 to 10 years.