There are basically 5 different types of hot water heaters that you should be familiar with so that you can make an informed choice given your family’s hot water usage needs.
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Tanked Water Heaters
Conventional Storage Tank Water Heaters
Tank style water heaters are by far the most common that you will find in most homes. Hot water heaters are an excellent conductor of heat, it only needs 40 minutes to heat 40 gallons of cold water. These units can run on oil, natural gas, propane or electricity.
The water is insulated inside a tank and kept heated at all times for delivery. The unit is always on and using energy albeit at a very slow rate to maintain water temperature within about 10 degrees of the unit’s thermostat setting.
The main water supply enters from the top of the tank and a dip tube extends that line to the lower section of the tank. When hot water is called for in the house, water in the tank begins to flow through your home’s plumbing system through a second pipe on the top of the tank.
A separate chamber below the main tank contains the unit’s heating element which is controlled by a thermostat. For natural gas and propane tanks, there’s a burner control. As the hot water in the tank is exhausted, the burner at the bottom ignites to heat incoming fresh water.
Little or no hot water is available during this recovery time. Storage type tanks provide a relatively low install cost with a variety of sizes to serve small and large homes. They have respectable flow rates to deliver domestic hot water into your home.
Because of its size, a storage tank water heater is usually located in a home’s utility closet or garage. It’s not always located within a centralized location of a home’s floorplan.
As a result, delivering hot water through a home can take can take a few minutes. This is a condition called “lag time” which all water heaters experience to some degree.
However, this lag time wastes several gallons of unused water and can be inconvenient for you as a homeowner. Gas water heaters cost more upfront but they tend to be more energy-efficient in the long run.
Heat Pump (Hybrid)
Heat pump water heaters use a small amount of electricity to move heat from the surrounding air to the water. They can deliver hot water up to 2 1/2 times more efficiently than a common electric resistance water heater.
Heat pumps work by moving heat from the air in the room to water in the tank. A fan draws air across a radiator-like device called an evaporator. The heat in the air is absorbed by a vaporous refrigerant flowing through the evaporator.
The refrigerant is then compressed raising its temperature and pressure. As a hot gas, the refrigerant then flows through the condenser where it transfers its heat to the water inside the water tank.
The refrigerant changes state from a gas to a liquid as it goes through the condenser and flows and flows back to the evaporator to start the cycle over again.
In the home’s water system, cold water gets cycled into the bottom of the tank where it absorbs the heat from the refrigerant and exits near the top of the tank as hot water.
Although savings can vary depending on your family size, hot water usage, and cost of electricity savings are estimated to be between $40 and $270 every year for a family size of 4. It is not uncommon for a heat pump to pay for itself in as little as 4 years with these types of savings.
Hybrids do not come without their share of challenges. They are not great choices for very cold climates and need to be installed in home environments where the temperature remains between 40 and 90 degrees Fahrenheit year around.
Another consideration that you must keep in mind is the amount of space you will need for clearance because the heat pump is housed on the top of the heater., normally around 7 feet from the base of the floor to the ceiling. Also, you’ll need to make sure there is enough uncooled space so that the heater can capture enough heat from the air.
You will need clearance around 7 feet from the base of the floor to the ceiling. Also, you’ll need to make sure there is enough uncooled space available so that the heater can capture enough heat from the air.
Condensing Water Heaters
Condensing water heaters work just like conventional tank water heaters but they differ in that they are able to recapture the heat from the flue gases that is normally wasted. They achieve the task by removing the heat from the burning fuel as well as cooling the combustion products.
The vapor of water generated by the burning of gas in the heater will condense back into the water and any latent heat from vaporizing will be released from the water. Latent heat is an enormous source of energy.
These units will only work with gas water heaters. You need a larger unit, at least, 55 gallons or larger.
Solar Water Heaters
Solar hot water takes the sun’s heat and turns it into usable thermal energy. When the collectors on your roof are warmer than your water tank a differential temperature controller activates a pump. This pump then circulates a non-toxic anti-freeze up to the solar collectors on your roof.
This pump then circulates a non-toxic anti-freeze up to the solar collectors on your roof where the fluid heats up. The solar heated fluid then pumps is then pumped to a super insulated storage tank where it gives off its heat as its passes through a heat exchanger.
It’s then pumped back to the roof to continue the cycle as long as the sun is shining. From May to September all of the water that you use for washing dishes, clothes or taking showers will be provided by the sun’s rays even on cloudy days.
In the darker months of Winter, the sun will still help out but a backup unit such as a boiler or electrical unit will run to ensure a steady supply of hot water is available for use. Instead of running all Summer, your boiler will only fire up when it is required as a backup unit heating the second coil in the upper part of your tank.
Instead of running all Summer, your boiler will only fire up when it is required as a backup unit heating the second coil in the upper part of your tank.
Overall, expect about 80% of your home’s water heating to come from the sun, saving you a lot of money on electricity each year. In fact, for most homes a solar heating system will pay for itself in 7 to 8 years. The cost of electricity in your area may go up but the sun will always be free.
The cost of electricity in your area may go up but the sun will always be free.
Tankless Water Heaters
Tankless (On-Demand or Continuous) Heaters
Tankless water heaters are a relatively new way to provide domestic hot water to a home. They are sometimes referred to as on-demand or continuous hot water heaters. Tankless units are designed to deliver hot water only when it is called for.
According to the Propane Education & Research Council tankless water heaters, especially those provided by fueled by propane save on energy and water and emit fewer greenhouse gases than conventional storage type electrical water heaters.
Tankless water heaters are available in both electric and gas. Tankless heaters use a compact metal cabinet instead of a tank. Because there is no preheated or stand by water to manage there’s no reason to insulate the cabinet to maintain a level of heat.
Instead of being always on, a tankless unit only uses energy when there is a demand for hot water. Otherwise, the unit is off and this difference accounts for the bulk of the energy savings and reduced emissions afforded by tankless water heaters.
When hot water is called for by an appliance or faucet cold supply water flows into and through the unit. In gas heaters, the burner ignites and the water circulates through a heat exchanger coil. In electric units, water enters and goes through a coil of heating elements.
The water heats up immediately and since there is not tank to fill there is no end to your supply of hot water. The wall hung design can also free up needed space for additional storage. These units run on natural gas, propane and electricity.
Tankless water heaters, although more energy-efficient, will only provide a limited amount of hot water per minute – about 4 gallons.
They are best for homes powered by natural gas when heating the water because many homes may not be equipped for the expensive electrical upgrade required for electric tankless heaters.
If you have a very large family who will be drawing hot water from multiple places simultaneously tankless water heaters may not be the optimal solution. Also, these tanks are twice the price as conventional storage tank water heaters.