Buying a New Water Heater
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Sometimes the old water heater just won't do the job. Either it's too small or it's seen better days. You can take this opportunity to get a more efficient new water heater—and perhaps change to an energy-saving plumbing distribution system at the same time.
What Type to Get
Don't just get the same type of heater you had before. Look over the options discussed in the Equipment Guide at the end of this chapter to decide what would really be best for you. Also consider which type of fuel you want. In most places, electric water heaters are more expensive—often a lot more expensive—to operate than gas ones.
If you currently have an electric-resistance water heater, consider switching to gas or to a heat pump water heater. If your system is combined with your house heating boiler, you'll probably want to keep it until you decide to replace the boiler (see chapter 8: Heating).
Once you've decided what type of water heater you want, look for the one that will save you the most on your energy and water bills.
Once you know what type of system you want, it's wise to get as efficient a unit as you can afford. Use the yellow Energy Guide labels to aid your purchase, and pay attention to other measures of efficiency.
There are many different kinds of efficiency, but the most important is Energy Factor, or EF. This rates how much of the fuel's energy comes out of the tap in hot water, under average conditions. In other words, if a gas-burning heater could use all the energy in the gas for heating water, and could then get that water to the tap without losing any heat, the tank would have an EF of 1.0. The Energy Factor takes into account heat lost up the flue, heat lost from the water sitting in the tank, and how much of the fuel's energy gets captured in the first place. The most efficient gas-fired water heaters will have EFs of .63 or higher, while some units heated by electric heating elements, which produce no combustion waste to escape up a flue, have EFs above .96.
Water heater efficiency ratings don't tell you which fuel is most energy-efficient, or cheapest, to use. Decide which type of fuel you want first. Then select the unit with the highest Energy Factor among different models that use that fuel.
If the unit is gas, oil, or propane fired, get a tank with at least R-16 insulation. Get at least R-22 for an electric-resistance unit. With this much internal insulation, you won't need to wrap the tank in a blanket. Internal insulation is also more effective than an external blanket because the coverage is more complete.
There are several ways you can save money when you buy a water heater. First, check whether your utility is offering rebates or other incentives for efficient water heaters. Also, consider the cost over the life of the unit—not just the initial price tag. Systems that are cheaper to buy can cost far more to operate. It's worth looking into different fuels and higher-efficiency units to reduce operating costs. For instance, if a .8 EF unit costs you $390 per year in energy, a .9 EF will cut that to $351. The savings add up, considering that a properly maintained water heater can last more than 30 years.
Finally, make sure that the storage tank has an accessible anode. Some tanks have the hex head of the anode rod hidden under the sheet-metal top. This makes changing the anode an adventure, rather than a bit of routine maintenance.
From Tank to Tap: Distribution
A great water heater won't do you much good if the water gets cold in the pipes. Any time is a good time to insulate pipes, but it's easiest to insulate when you are changing the plumbing, since pipes affixed to, or inside, walls and ceilings are harder to wrap with insulation. Insulating foam or fiberglass pipe sheaths usually come with a lengthwise slit, so you just snap them on around the pipe.
You should insulate hot-water pipes throughout the house. In addition, wrap the first 5 feet of the cold-water inlet (or as much as is accessible) at the water heater. Hot water tends to rise into the cold-water inlet, cool off, and drop back into the tank. Thermal traps also help to reduce this effect.
If your remodel involves extensive plumbing work, you can make dramatic changes in the hot water distribution system. Conventional or branch hot-water piping has a large main line with a number of smaller branches. These pipes contains gallons of water that cool down as they sit in the pipes.
Manifold distribution systems have small-diameter pipes from the manifold disbribution point to each appliance and tap. Each line contains much less water, so less water and time is wasted before hot water arrives. Bear in mind that smaller-diameter runs may mean more time to fill bathtubs or spas, and they should not be used if water pressure is low.
In order to have hot water at the faucet faster, some people with large homes put in recirculation systems that keep hot water constantly circulating in the pipes. This gives the user almost instantaneous hot water at any fixture in the house, saving time and water. However, this sort of system wastes a lot of energy, since hot water circulating through the pipes continually loses heat. It also uses energy to pump the water through the system.
To save some of this energy, you can purchase a recirculation system that only comes on when you push a button in the bathroom, kitchen, or laundry room; or you can get one that operates on a timer or thermostat sensor. A thermostat sensor will turn on the recirculation system when the temperature in the pipes drops below a certain level. Of these options, the manual control (pushing the button when you'll need the hot water) uses the least energy.
Another option is a device installed under the sink that circulates standing water from the hot pipe into the cold pipe and back to the water heater. When hot water arrives, the device automatically switches off, and hot water is ready at the tap. This doesn't require the extra pipe runs used by other recirculation systems.
Excerpted with permission from No-Regrets Remodeling by Home Energy (1997)