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Background
Most people in North America currently use a storage tank water heater to provide hot water in their homes. A storage tank water heater keeps water hot 24 hours a day, even while you’re at work or sleeping.
A tankless water heater (or "demand" water heater), on the other hand, does not store hot water. It heats the water as you use it. Tankless water heaters, come in a variety of sizes for different applications and are available in propane (LP), natural gas, or electric models.
“But, Did You Know . . . ?”
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The new load of a tankless water heater can sometimes equal the load of an entire new home!
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Progress Energy designs your neighborhood electrical system to meet the electrical needs of a typical residential neighborhood. However, if a customer installs a tankless water heater, the increased electric demand may exceed the design specifications of the system and require an upgrade of the cable and transformer. Utility regulations specify the method by which the additional cost for the system upgrades (called "Contribution in Aid of Construction") will be charged directly to the customer. If a customer installs a tankless water heater, the customer is required by approved tariff in both the Carolinas and Florida to pay the full cost to upgrade their facilities (including cable and transformer) to meet the need.
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Customers complaining about a voltage fluctuation or flickering lights may be seeing the impact of a tankless water heater in their neighborhood. It is important to note that this voltage fluctuation may be noticed by other customers in addition to the customer with the tankless water heater – since several customers often share a single transformer. An investigation of all customers on the transformer may be necessary to determine the source of the problem. If voltage problems exist because of a tankless water heater and a facility upgrade is necessary, the customer is required to pay the full cost to upgrade prior to construction.
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What are the energy requirements for tankless water heaters?
Electric heating element and gas requirements for tankless water heaters are much larger than for storage water heaters. A typical gas storage water heater has a gas input of 40,000 Btu/h. A gas tankless heater, though, may use up to 170,000 Btu/h and so may require larger gas lines and vents than conventional water heaters. Similarly, although a typical residential electric storage water heater draws typically 4,500 watts, a whole-house electric tankless heater can draw as much as 28,000 watts.
How much could I save with a tankless water heater?
There's a possibility of a savings from 2 to 3 percent of your energy bill because you heat the water only when it is needed. But the extra costs of installing the unit and possible costs of upgrading the local electrical system may far exceed the savings on an electric bill. And, depending on the type of electric rate you are on, a demand water heater may impact your peak demand and actually increase your electric bill.
How easy is it to install a tankless water heater?
Whole house tankless water heaters can be installed centrally to the point of use, such as under a sink. Tankless gas water heaters generally require a vent for the combustion heat and gases. Because of the power draw, multiple circuits and/or heavier wire will be necessary for installation of electric units. Installation by trained professionals who understand the technical issues of sizing, installing and safely venting a tankless water heater is essential.
What are the benefits of having a tankless water heater?
Tankless water heaters are compact in size and virtually eliminate standby losses. They can provide warm water at remote points of use and less water is wasted while waiting for warm water to reach a remote faucet. A tankless water heater can provide unlimited hot water as long as it is operating within its capacity.
What is the approximate cost of tankless water heaters?
Tankless water heaters range in price from $200 for a small under-sink unit up to $1000 for a gas-fired unit that delivers 5 gallons per minute. Typically, the more hot water the unit produces, the higher it will cost. The installation costs of tankless water heaters are from 2 - 4 times higher than tank-type water heaters. For gas tankless hot water heaters, the same gas supply line and/or venting may need to be sized larger than for a typical gas tank. Electric tankless water heaters draw more power and will require multiple circuits and/or heavier cable, which will increase installation costs.
What are the limitations of having a tankless water heater?
Electric units will draw more instantaneous power than tank-type water heaters. If electric rates include a demand charge (ie Time-of Use Rate), operation may be more expensive. More complicated electronics in tankless systems may require more attention than conventional tank units. You'll see the major limitation of electric point-of use heaters: they don't supply enough hot water for major end uses, such as dishwashers and showers. In fact, their usefulness is pretty limited to sinks. Even the electric unit's labeled "whole-house" can only serve a single shower or two sinks. More information on tankless water heaters.
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