Water Heating Fact: Water heating is the third largest energy expense in your home (after space heating and cooling). It typically accounts for about 14% of your utility bill. You can reduce energy consumption by 50%.
Best Features:
* If your gas water heater is more than 10 years old, its efficiency is probably no higher than 50%. It would be cost-effective to replace your old water heater with a new, higher-efficiency model. In selecting your water heater, keep these tips in mind:
* Select the appropriate first-hour rating (FHR).
* Look for the Energy Guide label.
* If you are in a moderate climate (i.e., with relatively low heating loads), consider a Heat Pump Water Heater (HPWH).
* Owning a larger tank doesn't necessarily mean a higher FHR.
* Everything else being equal, select a water heater with the highest energy factor (EF).
There are a number of technologies available to heat water efficiently. However, before implementing these technologies, it's important to first reduce hot water use with water-saving fixtures and appliances. Conserving water and heating it efficiently should be addressed during your whole-building design process. Water heating technologies include:
* Conventional Water Heating Efficiency
* Drain water Heat Recovery
* Heat Pump Water Heating
* Demand (Tankless or Instantaneous) Water Systems
* Solar Hot Water Heating
There are four ways to cut your water heating bills:
* Use less hot water
* Turn down the thermostat on your water heater
* Insulate your water heater
* Buy a new, more efficient water heater.
A family of four, each showering for 5 minutes a day, uses 700 gallons of water a week; this is enough for a 3-year supply of drinking water for one person. You can cut that amount in half simply by using low-flow aerating showerheads and faucets. These tips will help take the guesswork out:
* Install aerators in faucets and low-flow showerheads so you can reduce your hot water consumption by half.
* Lower the thermostat(s) on your water heater to 120°F.
* Do not install the water heater in an unheated basement, whenever possible.
* Locate the water heater where the length of piping runs to your bathroom and kitchen is minimized.
Solar Water Heaters: See Solar Water Heaters section. If you heat with electricity and you have an unshaded, south-facing location (such as a roof) on your property, consider installing a solar water heater. More than 1.5 million homes and businesses in the United States have invested in solar water heating systems and over 94% of these customers consider the systems a good investment. Solar water heating systems are also good for the environment. Solar water heaters avoid the harmful greenhouse gas emissions associated with electricity production. During a 20 year period, one solar water heater can avoid over 50 tons of carbon dioxide emissions.
Solar water heating is a renewable energy technology that is well proven and readily available and has considerable potential for application at Federal facilities. Solar water-heating systems can be used effectively throughout the country and most facilities will have an appropriate near-south-facing roof or nearby unshaded grounds for installation of a collector. A variety of types of systems are available and suitable for many applications. For example, low-temperature unglazed systems can heat swimming pools and associated hot tubs or spas, saving money on conventional heating or extending the swimming season. In mild climates, passive systems without pumps or electronic controllers can provide low-maintenance hot water for facilities with limited or expensive utility service. High-temperature parabolic-trough systems can economically provide hot water to jails, hospitals, and other facilities in areas with good solar resources that consistently use large volumes of hot water. And active flat-plate systems can service any facility in any area with electric or otherwise expensive conventional water heating.
When shopping for a solar water heater, watch for systems certified by the Solar Rating and Certification Corporation (SRCC) or the Florida Solar Energy Center (FSEC). 
| Figure 40: Hot Water Usage
(based on national averages)
The typical U.S. homeowner's water consumption by place of use. |
Conventional Water Heating Efficiency Most commercial water heating is done with storage water heaters that use gas, oil or electricity. Ranging in size from 20 to 80 gallons (75.7 to 302.8 liters), storage water heaters remain the most popular type for residential heating needs in the United States. A storage heater operates by releasing hot water from the top of the tank when the hot water tap is turned on. To replace that hot water, cold water enters the bottom of the tank, ensuring that the tank is always full.
Because the water is constantly heated in the tank, energy can be wasted even when no faucet is on. This is called standby heat loss. Newer, more energy efficient storage models can significantly reduce the amount of standby heat loss, making them much less expensive to operate. To determine the most energy efficient model, consult the EnergyGuide label required on storage water heaters. EnergyGuide labels indicate either the annual estimated cost of operating the system or energy efficiency ratings.
The efficiency of most gas water heaters currently in use is about 65% and standby losses are about 6.5% of stored capacity per hour. An accepted measure of the energy performance of water heaters is the energy factor (EF), which takes into account thermal losses from the tank. The National Appliance Energy Conservation Act (NAECA) has established minimum energy factors for water heating equipment used in residential applications, and since many commercial applications use the same type of water heating equipment, water heaters in commercial applications tend to fall under the NAECA minimum performance standards.
Criteria for Selecting a Water Heater: As with any purchase, balance the pros and cons of the different water heaters in light of your particular needs. There are numerous factors to consider when choosing a new water heater: fuel type, capacity, efficiency, and cost.
Determining Capacity: Although some consumers base their purchases on the size of the storage tank, the peak hour demand capacity, referred to as the first-hour rating (FHR) on the EnergyGuide label, is actually the more important figure. The FHR is a measure of how much hot water the heater will deliver during a busy hour, and it is required by law to appear on the unit's EnergyGuide label. Therefore, before you shop, estimate your household's peak hour demand and look for a unit with an FHR in that range.
Gas water heaters have higher FHRs than electric water heaters of the same storage capacity. Therefore, it may be possible to meet your water-heating needs with a gas unit that has a smaller storage tank than an electric unit with the same FHR. More efficient gas water heaters use various nonconventional arrangements for combustion air intake and exhaust. These features, however, can increase installation costs.
Rating Efficiency: Once you have decided what type of water heater best suits your needs, determine which water heater in that category is the most fuel efficient. The best indicator of a heater's efficiency is its Energy Factor (EF), which is based on recovery efficiency (i.e., how efficiently the heat from the energy source is transferred to the water), standby losses (i.e., the percentage of heat lost per hour from the stored water compared to the heat content of the water), and cycling losses.
The higher the EF, the more efficient the water heater. Electric resistance water heaters have an EF between 0.7 and 0.95; gas heaters have an EF between 0.5 and 0.6, with some high-efficiency models around 0.8; oil heaters range from 0.7 to 0.85; and heat pump water heaters range from 1.5 to 2.0. Product literature from manufacturers usually gives the appliance's EF rating. If it does not, you can obtain it by contacting an appliance manufacturer association.
Some other energy efficiency features to look for are tanks with at least 1.5 inches (3.8 centimeters) of foam insulation and energy efficiency ratings shown on the EnergyGuide labels.
Comparing Costs: Another factor uppermost in many consumers' minds is cost, which encompasses purchase price and lifetime maintenance and operation expenses. When choosing among different models, it is wise to analyze the life-cycle cost - the total of all costs and benefits associated with a purchase during its estimated lifetime. Units with longer warranties usually have higher price tags, though. Often, the least expensive water heater to purchase is the most expensive to operate. |
