Water Heaters Guide

Published by Green by Design

A Green by Design Buying Guide – Water header Guide (PDF format)

Introduction

This Green by Design buying guide provides information on water Hot and Cold heaters to help you to make an educated decision in choosing a water heater that saves energy, water, and money.

The greatest demand put on water heaters is for bathing, showering, washing dishes, and washing clothes. To maximize the effectiveness of water heaters, connections, fixtures and appliances that are supplied with hot water must also be effective in their use of hot water and in reducing the loss of heat. Actions to reduce the use of energy and hot water are listed below, along with estimates of costs and benefits associated with the actions.

ACTION	COST*	BENEFIT*

Insulate the water heater	$10 – $20	Reduces heat loss by 25% – 45%. Savings of 4% – 9%.

Insulate hot water pipes	$.33 – $.50 per foot	Raises water temperature 2°F – 4°F.

Install heat traps	$10 – $30 per pair	Savings of $15 – $30.

Install timing mechanisms	$60	Savings of 5% – $12%.

Install a drain water heat recovery system	$300 – $400	Savings of 25% – 30%

Install fixtures with low water flow rates	$10 – $20	Savings of 25% – 60%.

Eliminate leaks	Varies	1 drop per second costs $1 per month.

Purchase energy efficient appliances

Water heater	$300+	Each 10% reduction in temperature setting saves 3% to 5% in energy costs.

Washing Machine	$400+	Savings of 30% 50%

Dishwasher	$300+	Savings of 50%

*Costs and energy savings are crude estimates that vary depending on the types of products, their installation and their actual use. Costs estimates are for one unit of a product and represent the low-end cost.

The ENERGY STAR label specifies that products meet strict energy efficiency guidelines. ENERGY STAR appliances are not only energy efficient, they have higher manufacturing standards and are likely to outlast low-cost models.

Water Heater Product Comparison

There are various types of water heaters that vary by size and fuel source.

Conventional (Storage tank)

A water tank is used to store, heat and distribute hot water. Gas and electric models typically hold 40 to 80 gallons of water.

Demand or Tankless (Instantaneous)

Demand water heaters heat water as it is distributed and do not require a water tank for storage. Demand tanks are 8% to 14% more efficient than conventional water heaters for households with high water usage (86 gallons per day) and 24% to 34% more efficient for households with low water usage (41 gallons per day). They may also be 27% to 50% more efficient when used with dishwashers, washing machines, and fixtures as dedicated point-of-use units.

Heat Pump

Heat pump water heaters distribute heat from the air to water rather than directly heating water. They are 33% to 50% more efficient than conventional electric water heaters.

Solar

Solar water heaters use heat from the sun to provide heat to stored water.

Tankless Coil (Indirect)

Tankless coil water heaters use heat from the home to heat water.

What Makes a Water Heater ‘Green’?

A green water heater uses less energy to heat water in the tank and then conserves the temperature of water stored in the tank. Federal standards for energy efficiency are established for all water heaters manufactured as of 2004, outlined below.

Standard	EF Rating

Electric Water Heaters	0.90 – 0.93

Gas Water Heaters	0.56 – 0.61

Energy Factor (EF) is the ratio of useful energy output from a water heater to the total amount of energy delivered to a water heater. The higher the EF rating, the more efficient the water heater. Gas water heaters equipped with electronic pilot lights are more efficient than those without.

Some water heaters are designed to heat water to 140°F. However, 120 °F is sufficient for most household needs. All conventional water heaters have a thermostat, which allows the temperature of contained water to be set.

Gas water heaters usually have a thermostat located near the bottom of the tank while electric water heaters may have two thermostats, one for each heating element, positioned behind a plate. The owner’s manual will provide the location and instruction on how to set the thermostat. You may get a rough estimate of the temperature of water output from a water heater by using a thermometer to measure the water temperature at the tap that is located furthest from the water heater.

Turn your water heater off or turn the thermostat down when the water heater is not going to be used for long periods of time, such as during a vacation away from home. Electric water heaters typically have a circuit breaker that may be simply switched to the off position. Gas water heaters have a pilot that must be put out. Be sure you know how to turn off the gas to the pilot and also know how to relight the pilot for continued use. Otherwise, hire a plumbing professional.

Water Heater Tank Insulation

The insulation used to insulate water heaters is measured in terms of its resistance to heat flow, otherwise known as its R-value. Insulation is recommended for water tanks with an existing insulation R-value that is less than R24. An insulation value of R8 should be used for additional insulation.

If R8 is not available, two layers of R5 insulation are sufficient. You should never insulate the top of a gas water heater because insulation is combustible. When insulating an electric water heater, the thermostat should never be set above 130°F because it could cause the wiring to overheat. It is also a good idea to install insulation underneath the tank of electric water heaters to prevent heat loss into flooring. However, this is best for new installations. Insulation should never obstruct a drain, flue or airflow.

Water Pipe Insulation

In addition to insulating the water heater itself, insulating all accessible hot water pipes throughout your home increases the water temperature in pipes and reduces heat loss from pipes. Piping within three feet of the water heater is of particular importance. Both hot and cold water pipes in this area should be insulated.

One of the following methods should be used for water pipe insulation:

Wrap specially designed pipe insulation around pipes
Tape, wire or clamp polyethylene or neoprene pipe sleeves around pipes
Tape fiberglass insulation around pipes

Acrylic tape is preferred over duct tape for securing pipe sleeves and insulation. Duct tape won’t hold over time.

Insulation should be at least six inches from the flue of a gas water heater. Piping within eight inches of the flue should consist of at least one-inch thick fiberglass pipe wrap, without facing. Wire or aluminum foil tape is recommended for this area.

Heat Traps

Heat traps, also known as anti-convection valves, are designed to prevent heat loss through inlet and outlet pipes attached to a water heater. Heat traps are valves (loops of pipe) that prevent unwanted flows of hot or cold water from the tank. Balls placed inside of the valves prevent convection. Convection is a process where heated water rises. Some newer water heaters have factory installed heat traps or they are provided as an option. Older model water heaters may be upgraded and equipped with heat traps. The installation of heat traps requires the ability to solder pipe joints and is best accomplished with the assistance of a certified plumbing professional.

Timing Mechanisms

Cost savings may be realized by installing a timer to switch a water heater’s thermostat off during times when hot water is not being used or during peak demand times specified by utility companies. Timers are most cost effective when a water heater is not equipped with a heat trap or the water tank and pipes are not insulated. Note that timers are not effective for gas water heaters since timers cannot affect the operation of pilot lights.

Utility companies also offer to install control devices that allow the utility to cut off high consuming electric appliances, such as electric water heaters and central air conditioners, during peak demand times. Some utility companies offer monetary incentives for allowing them to perform this service.

Drain-Water Heat Recovery

Drain-water heat recovery systems are designed to capture heat from used hot water and use that heat to preheat cold water that goes to the water heater or a hot water fixture. Systems are designed with and without storage tanks to hold the used water. A storage tank is required for use with a drain-water heat recovery system that supplies hot water to dishwashers and washing machines. Without storage tanks, heat recovery systems will only be capable to work during simultaneous water flows, such as at faucets and showers.

In this case, a heat exchange mechanism replaces a portion of the waste drain. Hot water going out of the drain is then used to heat incoming coldwater. With a storage system, hot water from the drain is run through a tube at the bottom of the storage tank. Since heat rises, the hot water will rise to the top of the storage tank. Incoming cold water is then circulated through tubing at the top of tank where the heated water is. Heat recovery systems provide for increased water heating. They assist with heating water when an undersized water heater is in place and they allow you to reduce the temperature setting at your water heater without affecting its performance.

Water Fixtures

Properly designed and installed water fixtures provide great costs savings for hot water use. Federal regulations govern the flow rate for newly installed showerheads and faucet fixtures as shown below.

FIXTURE	FEDERAL REQUIREMENT*

	Flow Rate**

Showerheads	2.5 gpm. @ 80 psi.

Bathroom faucets	2.5 gpm. @ 80 psi

Kitchen faucets	2.2 gpm. @ 60 psi

* New installations only **gpm = gallons per minute psi = pounds per square inch

These regulations govern plumbing systems installed as of 1992. However, older plumbing systems may be modified to achieve the same cost saving flow rates by installing new showerheads and faucets. Federal requirements specify the upper limit of flow rates. Consumers may actually purchase fixtures with lower rates than indicated.

Note that standards are established for specific water flow rates. Fixtures will not work properly if your water pressure is too low or too high. A water pressure gauge that allows you to regulate the water may need to be installed in order to achieve the desired water pressure. Consumers must first make sure that low pressure is not the result of a leak in the plumbing system.

Faucets

Most faucets have an aerator, a device that typically screws onto the tip of the faucet. Some faucets have aerators built into them while others are detachable. An aerator determines the flow of water from the faucet. Maximum water efficiency can be achieved with faucet aerators rated at less than 1.0 gpm.

Showerheads

There are two types of low-flow showerheads: aerating and laminar-flow. Aerating showerheads are designed to mix water with air to form a misty type of spray. Laminar-flow showerheads are designed to divide a single input water stream into individual streams of water. Under humid climate conditions, an aerating showerhead may produce more steam and moisture than is wanted. It is recommended that consumers who live in environments with high humidity purchase laminar-flow showerheads.

Plumbing systems installed prior to 1992 may have showerhead flow rates as high as 5.5 gpm. An easy method of testing your existing showerhead flow rate involves using a bucket and timer as follows:

Identify the one-gallon mark on a bucket
Place the bucket under your running shower
Turn your shower on to the pressure you normally use

2.5 gallons per minute
= 2.5 gallons per 60 seconds
= 1 gallon per 24 seconds.

Use the timer to time how many seconds it takes to fill the bucket to the one-gallon mark

If it takes less than 24 seconds to reach the one-gallon mark, you could benefit from a low-flow showerhead

Water Leaks

Leaks in water lines, connections, fixtures and appliances should be repaired or replaced immediately. Besides causing a loss of water, leaks may cause damage to your property and adversely affect the structural integrity of floors, walls, ceilings and other structures that come in contact with the leaking water. Leaks in your water heater’s tank are usually not repairable. As such, you will need to replace your water heater if the tank leaks water.

Other Appliances

Water heaters alone will not help consumers to realize great cost savings unless they also purchase energy efficient washing machines and dishwashers. The real benefit comes from the installation of these appliances when they are able to reduce the amount of energy necessary to heat the water they use. All ENERGY STAR compliant appliances are energy efficient. They may require a higher purchase price, but they cost less to operate and will pay for themselves in the long run. Energy efficient washing machines and dishwashers include an Energy Guide label that indicates their energy use. Though compact appliances always indicate lower energy usage, the lower use can only be achieved if appliances are used properly.

Washing Machines

Washing machines that allow for a range (cold-warm-hot) of temperatures and varying load sizes provide the most energy efficiency. About 80% of the energy consumed by a washing machine is used to heat water. Most detergent manufactures produce detergents that provide optimal cleaning with cold water. Cold water is always sufficient for rinsing clothes and cold-water washing allows clothes to last longer. Energy efficient washing machines will also spin clothes dryer thereby reducing the amount of energy used for drying. Consumers should seek front-loading washing machines since they use less water than top loading machines to achieve the same result. Washing machines come in a variety of sizes and those compact machines with the lowest energy rating will not be of benefit if you are forced to wash more loads. It is important to consider your typical load size when choosing a washing machine.

Dishwashers

There are two categories of dishwashers- compact and standard. Compact dishwashers hold smaller loads of dishes. Standards dishwashers hold larger loads and thus, require more water and energy for use. However, consumers who use compact dishwashers multiple times throughout the day and without full loads may actually be paying more than if they were using a standard sized dishwasher.

Some of the most energy efficient dishwashers include a booster heater. A booster heater is a device that raises the water temperature input to a dishwasher to 140 °F, the recommended temperature for washing dishes. Dishwashers that also allow short cycles reduce hot water and energy consumption when such a cycle is sufficient for the load.

Summary

An energy efficient hot water heater is most effective if connections, fixtures, washing machines and dishwashers are also energy efficient. Water heaters are the only major houehold applicance that are not addressed by the ENERGY STAR program. However, the Department of Energy (DOE) is in the process of implementing such a program. Other federal regulations govern water heaters and dictate their EF rating as shown at in this guide. Consumers should seek the ENERGY STAR label for all other appliances referenced in this guide.