LIGHTING AND APPLIANCES: Water Heating

Questions:

• What should I look for when buying a new water heater?
  
• How do you select the proper size for a water heater?
  
• How can I reduce my water heating costs?
  
• What can you tell me about tankless water heaters?
  
• What should I do to keep my water heater operating at maximum efficiency?
  
• Should I use a water heater insulation blanket with my new water heater?
  
• Can you vent a water heater to an old masonry chimney?

What should I look for when buying a new water heater?
In general, about 20 percent of the energy consumed by an average home is for water heating. Water heaters have improved significantly in the last 12 years and are much more energy efficient, primarily due to more efficient combustion for gas models and added insulation.

Because the average life expectancy of a water heater is about 13 years, it is important to consider purchasing one that is energy efficient since energy-efficient models mean reduced energy consumption, which results in lower energy costs.

Most water heaters and other home appliances come with a large yellow sticker called the ENERGYGUIDE. This sticker compares average yearly energy operating costs for different models, telling consumers which ones are expected to cost the least during their lifetimes.

Also, most water heaters come with an Energy Factor (EF) value, which is listed on a separate tag beside the ENERGYGUIDE. The EF is a decimal value between 0.4 and 1.0 and is the amount of energy supplied to the heated water, divided by the water heater's total energy consumption. Gas water heaters have EF values between 0.5 and 0.7, while electric ones range from 0.75 to 0.95. Minimum EF values range from 0.51 to 0.56 for gas units, depending upon the size of storage tank, to an average of 0.89 for electric ones. Recommended EF values are 0.61 for gas units and 0.92 for electric water heaters.

All type of water heating units with higher EF values generally cost more initially, but because of the higher EF value, will more than makeup for this higher initial cost in yearly energy savings throughout the lifetime of the water heater.

How do you select the proper size for a water heater?
The size or capacity of water heater needed is based on the maximum amount of hot water consumed during any one-hour period. This is called the peak-hour demand.

To determine the peak usage hour for a family, list all the water consuming activities during that period.

Typical hot water consumption in gallons per usage for various activities is as follows: shower, 20; bath, 20; shaving, 2; hands and face washing, 4; hair shampooing, 4; hand dishwashing, 4; automatic dishwasher, 14; food preparation, 5; automatic clothes washer, 32.

The peak for one family might occur in the morning and consist of three showers (20 gallons each, 60 gallons total), hands and face washing (5 gallons), shaving (2 gallons), and food preparation (5 gallons), for a total of 72 gallons.

A water heater can provide more than its storage capacity during the first hour of operation, because it can also heat the water during this period. This capacity, the total gallons of hot water the heater provides during this first hour, is referred to as the first-hour rating.

In the sample above, a water heater with a first-hour rating of at least 72 gallons would be required.

Residential water heaters are most commonly available in 20, 30, 40, and 50-gallon capacities with first hour-ratings ranging from 22 to 100 gallons. Gas and propane water heaters typically have higher first-hour ratings than electric heaters of the same storage capacity.

How can I reduce my water heating costs?
Several simple things can be done to decrease the amount of energy used to heat water in a home. Water heaters consume about 20 percent of the energy an average home uses, with more than one-third used in showering and 25 percent to wash clothes.

Implementing certain energy-efficient measures, even small ones, can make a noticeable difference in the heating bill.

For example, water heater temperatures should be set to about 120 degrees and definitely no more than 130 degrees. In general, a 10-degree reduction in water temperature has been shown to provide an eight percent water-heating energy savings.

Another important and effective energy-saving measure is to wrap the water storage tank with an R-12 insulation blanket, especially if the water heater is an older model. Consult the manufacturer's equipment guide to make sure an insulation wrap is recommended; it may not be on some newer models. Also, insulate all exposed hot water pipes with either foam or fiberglass wrap.

Installing low-flow showerheads has been shown to save not only money in reduced water usage, but also to save energy as well.

Finally, when the time comes to purchase a new clothes washer, selecting one that is energy efficient will also save on water heating costs.

These energy-saving tips cost very little and have the potential to not only lower the amount of energy used to heat water in a home, but also save money as well.

What can you tell me about tankless water heaters?
Tankless, or demand, water heaters don't have storage tanks, so they heat water as it is used, on a demand basis.

Because there isn't a storage tank, this type of water heater can save from 10 to 20 percent on the cost of heating water.

A family of four uses about 100 gallons of hot water a day. During the course of a year, the cost to heat this amount of water will vary from $90 to $700, depending on the price of energy. If fuel prices are high, the savings gained from a tankless water heater will be significant. Tankless heaters are available in either point-of-use or central styles.

Point-of-use heaters are installed near each area that requires hot water. This minimizes plumbing for new construction. The other type, a central tankless heater, supplies water for the entire house. Tankless water heaters generally cost $200 to $500 more than conventional water heaters. While this may seem like a large premium to pay, the fuel savings may justify the additional cost during the course of just a few years.

What should I do to keep my water heater operating at maximum efficiency?
As with any heating or cooling device, regular maintenance of water heaters goes hand-in-hand with efficiency and safety. Follow these three steps to assure the water heater is giving maximum efficiency for minimum dollars.

1. Every two months, connect a hose to the bottom drain. Open the valve all the way, letting the water flush through. Be careful: this is hot water! This removes sediment, which reduces heating efficiency.

2. Place a bucket under the temperature and pressure (T-P) relief valve discharge, located on the top or side of the heater. Carefully lift the lever -- again, the water surging out will be hot. The T-P valve is a safety valve designed to prevent the tank from exceeding safe temperature and pressure levels. This test assures that sediment is not blocking the T-P valve.

3. If the unit is gas or electricity, annually inspect the heater's burner area, checking for dirt or water. If the area is dirty, shut off the pilot and clean the burner with a shop vacuum. Remember to light the pilot again. If there are signs of leaks, the water heater will probably have to be replaced, soon

If the water heater is more than and the bottom drain and T-P valve have never been checked, they may not seal properly once opened. Replace either valve if they do not seal tight after operation.

Should I use a water heater insulation blanket with my new water heater?
Residential water heaters must all meet minimum efficiency standards. For example, a 40-gallon, gas water heater must have an energy factor (EF) of at least 0.54, while an electric water heater must have an EF of at least 0.89.

While this is a considerable improvement compared to heaters marketed just a few years ago, there are water heaters on the market with EF ratings in the mid-60s or higher for gas and the mid-90s for electric.

If the existing water heater is on the low end of the efficiency rating, then it is still possible to reduce fuel cost effectively by adding an insulation blanket. However, if the water heater is on the high end of the efficiency range, then additional insulation will probably not be of much benefit.

Can you vent a water heater toan old masonry chimney?
The National Fire Code does not specifically prohibit the use of masonry chimneys with modern gas appliances. However, it requires the chimney to be lined with an approved material.

Many old masonry chimneys are not lined. Venting gas appliances into unlined chimneys could cause drafting problems for the appliance, as well as deterioration of the masonry.

It is recommended that gas appliances are vented with a properly sized and designed chimney. Check with local building code officials for their specific requirements.