Water Heating

Home , Storage water heater, Water heating

Technology Fact Sheet WATER HEATING

When a combustion-type hot water storage For more information, contact: WATER HEATING HOT WATER tank system is used, placing the tank in the RECIRCULATION SYSTEMS Energy Efficiency and following places may improve resistance to Energy-e Renewable Energy These devices Hot and cold water service backdrafting: fficient strategies for Clearinghouse (EREC) provide “instant” to sink supplying hot water in the home 1-800-DOE-3732 hot water at • Outside of the home’s conditioned space www.eren.doe.gov point sources (e.g., in garage). ENERGY-EFFICIENT WATER Or visit the BTS Web site at and provide • In a sealed, indoor mechanical room having Demand (tankless or instantaneous) water www.eren.doe.gov/buildings HEATING water cool adequate exterior ventilation. heaters—heat water directly without use of a water Domestic water heating accounts for between Written and prepared for conservation side storage tank. Demand systems produce a warm • Inside the conditioned space when a power 15 and 25 percent of the energy consumed in the U.S. Department of benefits. water limited amount of hot water—a 70°F water side venting system using a fan is incorporated to homes. Water-heating energy costs can be Energy by: Buildings for temperature rise is possible at a flow rate of Sensor expel combustion gases through the flue, managed by selecting the appropriate fuel and NAHB Research Center the 21st Century five gallons per minute through gas water Pump and/or a sealed combustion system water heater type, using efficient system 800-898-2842 heaters and two gallons per minute through separately ducts in outside air for combustion Buildings that are more design, and reducing hot water consumption. www.nahbrc.org Controls electric water heaters. These are best suited and ducts out combustion gas exhaust. energy efficient, comfortable, Southface Energy Institute and affordable…that’s the TYPES OF WATER HEATERS for low-demand or remote applications. 404-872-3549 REDUCING CONSUMPTION INSTALLATION AND MAINTENANCE goal of DOE’s Office of Building Storage-type water heaters, the primary focus Tankless coil water heaters—use a heat www.southface.org Simple use of water-saving appliances such as Always meet the minimum applicable Technology, State and within this fact sheet, are the most common exchanger integrated with a space-heating high-efficiency washing machines and U.S. Department of Energy’s Community Programs (BTS). ® mechanical, plumbing, electrical, and/or other domestic hot water (DHW) heating system boiler to heat water instantaneously. These are Oak Ridge dishwashers (look for the ENERGY STAR label), code requirements when installing a water To accelerate the development selected today. However, other types of water generally recommended for use only in an National Laboratory combined with flow-restricting devices such as and wide application of energy Buildings Technology Center heating system. Initial installation heaters may be very cost effective. extremely cold climate. faucet aerators and low-flow showerheads, efficiency measures, BTS: 865-574-5178 improvements include installing a second anode lowers household hot water consumption. Storage water heaters—heat and store water An indirect water heater is a tankless coil www.ornl.gov/ORNL/BTC rod (combination anode/hot outlet nipple) and • Conducts R&D on A recirculation system powers a pump to cycle in a tank ranging in size from 20 to 80 gallons. water heater with a separate storage tank to replacement drain valve (full-port ¾-inch technologies and concepts U.S. Department of Energy’s water through the plumbing loop between They offer a ready reservoir of hot water, reduce boiler cycling. When matched with a National Renewable Energy threaded brass ball valve with hose adapter). for energy efficiency, although “standby” energy losses are higher high-efficiency boiler, this becomes a most Laboratory water heater and faucet. This lessens the working closely with the Water heater placement can impact operating (303) 275-3000 amount of tepid water wasted down the drain building industry and with than with some other types. Conventional fuel efficient hot water system. www.nrel.gov/building_thermal while waiting for hot water. On-demand DHW cost, especially if the unit is poorly insulated. manufacturers of materials, sources include natural gas, electricity, systems recirculate water when a user trips a Unit placement to facilitate short, insulated equipment, and appliances propane, and fuel oil. HEAT PUMP WATER HEATER switch at the faucet. Once water of the desired piping runs to bathrooms and kitchens is most • Promotes energy/money Heat pump water heaters are electric storage Heat pump technology can provide cost- temperature reaches the faucet, the pump effective. To improve energy efficiency, saving opportunities to both water heaters that are two to three times as effective water heating in mild climates. storage-type water heaters are best located in shuts off. builders and buyers of homes efficient as conventional electric resistance conditioned space, except in extremely hot and commercial buildings units. Because they remove heat from the Heat WATER HEATING SYSTEM SAFETY climates where tank heat loss increases the in Cold water • Works with state and local surrounding air, they are most effective in trap Backdrafting—the pressure-induced spillage of cooling load. regulatory groups to improve warm climates. Hot water out exhaust gases into interior living space—is a Periodic water heater maintenance can building codes, appliance health and safety concern where combustion Combination space and water heating significantly extend water heater life and standards, and guidelines for water heaters are employed. To reduce such systems—are storage water heating systems minimize loss of efficiency over time. Routine efficient energy use NOTICE: Neither the United risk, employ one of the systems described providing space heating plus DHW. Separate Access States government nor any maintenance involves flushing a quart of water • Provides support and grants cover below, install a hardwired carbon monoxide water heaters and forced-air or hydronic agency thereof, nor any of their from the storage tank every three months, to states and communities employees, makes any warranty, (CO) detector nearby, and annually inspect systems may be combined, or a single-source express or implied, or assumes checking the temperature and pressure relief for deployment of energy- (clean, adjust, or repair if necessary) the system may be purchased. Because heating Temp/pressure relief valve Temp/pressure any legal liability or responsibility valve every six months, and inspecting the efficient technologies and Sacrificial annode rod burners, combustion chamber, and flue. needs of small, well-insulated homes often are for the accuracy, completeness, anode rod every three to four years. practices Thermostat or usefulness of any information, low, combination systems can be an apparatus, product, or process excellent choice. Drain valve disclosed. The views and opin- ions of authors expressed herein Storage tank Heat pump do not necessarily state or reflect Printed with a renewable-source ink on paper containing at least 50% wastepaper, including 20% postconsumer waste. those of the United States gov- OFFICE OF BUILDING TECHNOLOGY, STATE AND COMMUNITY PROGRAMS August 2001 DOE/GO-102001-0785 ernment or any agency thereof. ENERGY EFFICIENCY AND RENEWABLE ENERGY • U.S. DEPARTMENT OF ENERGY WATER HEATING

STORAGE TANK WATER HEATER SELECTION To determine the local cost, multiply the annual energy use inexpensive, do-it-yourself alternative to plumber-installed The lowest-priced water heater may be the most expensive to (in kWh or therms) found on the EnergyGuide label by local WATER HEATER INSULATING JACKETS heat traps. operate and maintain over its lifetime. And while an oversized Insulating the water heater is one of the best dollar-for- energy rates. Based on local utility rates, one type of water Drainwater heat recovery devices improve efficiency by warming unit may be alluring, it carries a higher purchase price and dollar energy-saving measures. heater may operate much more cheaply than another. incoming cold water with heat absorbed from draining warm increased energy costs due to increased stand-by losses. water. Recovery systems reclaim energy and can enhance hot Consider the following factors when buying a water heater: FIRST HOUR RATING/PEAK HOUR DEMANDS water system performance by increasing effective FHR and • Fuel availability, including natural gas, electricity, oil, and Heat trap Avg. gal. Times capacity. Benefits ultimately depend on many variables Gal. used propane Hot water use hot water used in in hour including installation, fuel type, system geometry, exchanger per usage hour • Cost—equipment, installation, and expected annual fuel cost characteristics, and usage patterns. s5howering 1x = • Capability—system capacity, including first hour rating (FHR) bathing 20 x = Flue dampers seal off the flues of naturally drafted gas water heaters when there is no exhaust to reduce heat loss up the flue. • Longevity—expected equipment life s2x=having washing hands & face 2 x = Timers can shut off electric water heaters for a set time period, • Safety, including possible combustion gas backdrafting s4x=hampooing hair Cut-outs for such as when time-of-use electric rates are highest or when concerns heating coil hand dishwashing 2 x = elements occupants normally do not use hot water. Depending on shutoff The FHR is the amount of hot water the heater can supply per a4utomatic dishwashing 1x = time, setpoint, and tank insulation level, timers may or may not be hour (starting with the tank full of hot water). The FHR depends preparing food 5 x = cost-effective. In addition, they may be inconvenient when much on the tank capacity, source of heat (burner or element), and c2lothes washing 3x = hot water is needed while the water heater is turned off. size of the burner or element. To select the correct size water P)EAK HOUR DEMAND (total gal used in hour = heater, use the FHR—not tank capacity. Using the table Cut-out for Load management devices enable utilities to turn off electric EXAMPLE Electric combustion air Gas water heaters remotely during periods of heavy electrical provided, first estimate the daily peak one-hour hot water A typical household's peak hour of hot water usage might entail: demand for the house. Then try to choose a model with a FHR demand. Allowing this option to be installed, where available, 25showers 1x2=03 IMPROVING WATER HEATER EFFICIENCY within about 2 gallons of this peak demand. typically results in a monthly credit from the utility. 2 shampoos 4 x 2 = 8 With any DHW system, methods for reducing hot water cost

The energy factor (EF) indicates overall unit efficiency based on 12x1=2shaving start with lowering the thermostat. Set the thermostat low the amount of hot water produced per unit of fuel consumed enough to minimize safety concerns (scalding) yet high enough 2 hand/face washing 2 x 2 = 4 over a typical day. While higher EF values generally equate with for washing (dishes, clothes) and bathing. A setting of 120°F DRAINWATER HEAT RECOVERY S15x1=5ofuorocd prep higher efficiency, they do not always mean lowered operating e: Gas generally meets most household needs. *Th Appli This system captures waste heat through heat exchange e abov ance M P)EAK HOUeRcDhEaMAND (totaanlugfal used in hour =94 cost, especially when fuel sources are compared. rt assu cturer mes n s Asso Installing water heater insulating “jackets” of R-11 or higher can from the wastewater drains. o wate ciation r cons Information on annual energy use and average operating cost ervatio be cost effective in reducing standby losses on storage-type units, n mea sures. can be found on the EnergyGuide label on new water heaters. especially older or poorly insulated ones. Greater benefit is Faucet achieved when the hot water tank is installed outside of conditioned space (e.g., garage). For safety, however, never block any

STORAGE WATER HEATER COMPARISON controls, valves, or airways for combustion or exhaust. Preheated cold water to plumbing fixtures and to water Pipe insulation is inexpensive and easy to install. Add it to hot heater and cold water pipes in unconditioned spaces such as garages, Heat exchanger

attics, and crawlspaces and for a distance of at least six feet Hot water from the tank. Cold water in Heat traps prevent heated water in a storage tank from mixing with cooled water in pipes, a process called thermosiphoning. Drain water Some new water heaters have built-in heat traps, although they can be added to new or existing water heaters. Flexible Hot water tank connectors with a loop in the vertical line offer an effective,

Based on a family of four, electricity at $0.08 per kWh, natural gas at $0.60 per therm, and propane at $1.00 per gallon (prices often vary seasonally). WATER HEATING

Based on a family of four, electricity at $0.08 per kWh, natural gas at $0.60 per therm, and propane at $1.00 per gallon (prices often vary seasonally). Technology Fact Sheet WATER HEATING

any legal liability or responsibility valve every six months, and inspecting the efficient technologies and Sacrificial annode rod burners, combustion chamber, and flue. needs of small, well-insulated homes often are for the accuracy, completeness, anode rod every three to four years. practices Thermostat or usefulness of any information, low, combination systems can be an apparatus, product, or process excellent choice. Drain valve disclosed. The views and opin- ions of authors expressed herein Storage tank Heat pump do not necessarily state or reflect Printed with a renewable-source ink on paper containing at least 50% wastepaper, including 20% postconsumer waste. those of the United States gov- OFFICE OF BUILDING TECHNOLOGY, STATE AND COMMUNITY PROGRAMS August 2001 DOE/GO-102001-0785 ernment or any agency thereof. ENERGY EFFICIENCY AND RENEWABLE ENERGY • U.S. DEPARTMENT OF ENERGY