Water heaters can have a tremendous impact on energy bills. They are second only to living-space heating systems in the amount of energy they consume. You can lower water heating costs by installing low-flow showerheads and faucet aerators, insulating your hot water tank and pipes, and using a water-saving ENERGY STAR® qualified clothes washer. There are five basic types of water heaters:

STAND­ALONE STORAGE TANK SYSTEM

This is the most common type of water heater, typically using electricity, gas or oil to heat the water. Gas or oil water heaters offer relatively fast recovery times and relatively low operating costs when compared to electric water heaters. Electric water heaters are the least expensive to install and are a convenient solution for houses in which it's difficult to vent a gas or oil water heater. However, electric water heaters may be expensive to operate.

TANKLESS COIL

Common in houses with boilers, a tankless coil heats water right in the boiler. There is no storage tank with this kind of system, so the boiler has to fire up almost every time someone turns on a hot water faucet. This makes it a very inefficient water heater if the boiler is not already firing to provide living-space heat. Also, it usually can't provide sufficient hot water for more than one use at a time. Its advantage is that it is the least expensive type of water heater to install if a boiler is present.

INDIRECT-FIRED STORAGE TANK

For homes with a boiler, a very cost-effective and efficient way to provide hot water is with a storage tank operated as a separate zone off the boiler. This is called an indirect-fired storage tank. This type of system combines the advantages of having a separate storage tank, having a single appliance for heat and hot water, and using a fuel that generally costs less than electricity. Even though the boiler will come on during the summer months, this is usually a much more efficient method of getting your hot water than with a separate, stand-alone water heater. Some boilers have optional controls such as "cold start" or "outdoor reset," which can increase efficiency. Your heating contractor can help you choose appropriate controls for your system.

INSTANTANEOUS/ON-DEMAND WATER HEATER

These are more efficient than standard storage tanks because they make hot water only when needed, and there is no tank full of water to keep warm. Electric models are costly to operate and require a separate 100-or 200-amp service. Most models generally work well but can be limiting because of their minimum flow rates (typically a half-gallon per minute to activate the unit). Check the specifications for the model you are considering to be sure that it is right for you. Better instantaneous water heaters will have electronic ignition to reduce energy use, along with modulating flames to ensure steady temperature delivery over a wide range of flow rates. Instantaneous water heaters are prone to sediment buildup. Because of the amount of mineral content in Vermont's water, it is highly recommended to have an in-line water filtration system installed before purchasing an on-demand water heater. If this is not possible, install the water heater so that it can be easily flushed each year.

SOLAR WATER HEATER

Even with Vermont's short, cloudy winter days, solar energy can cost-effectively meet most of the water heating energy needs of a typical household. A properly designed, installed and maintained system can provide about two-thirds of the hot water you'll typically need year-round and all of the hot water you'll need during the summer. Solar water heaters require a fossil-fuel or electric backup system for extended cloudy periods. They also require a large storage tank so that reliance on the back­up system is minimized.

BUYING A NEW WATER HEATER:

When installing any water heater, it is a good idea to have the unit plumbed so that it can be easily maintained and periodically flushed. Fuel costs vary widely from year to year, so have a cost comparison done to determine whether an oil, propane, or electric water heater will be most cost-effective for your home. Efficiency Vermont can provide this cost comparison for you. When shopping for a new water heater, keep these points in mind:

Gas or Oil Water Heaters

• Every water heater has an Energy Factor rating (EF). The higher the number, the more efficient the water heater. Efficiency Vermont recommends purchasing a water heater having an EF of at least .61 for gas, or .64 for oil. On-demand gas or oil water heaters can have an EF of .80 or more.
• On-demand water heaters should have electronic ignition (no standing pilot) and modulating (or varying) output.
• The water heater should have a dedicated outside combustion air source to its burner. This will reduce the potential for back-drafting of combustion by­products and help to ensure proper fuel combustion.
• Oil water heating equipment requires additional safety shutoff devices to be installed by the contractor.

The installation contractor should:

• Size the system using the "first hour rating" to make sure that the unit can supply the amount of hot water that your household needs.
• Provide all the materials and labor necessary for a safe and complete installation of the specified water heating system.
• Inspect the chimney, if applicable, and determine that it is safe for water heating equipment installation.

Indirect-Fired Water Heater