| Q.1 |
How do I know if the water heater I want to buy is energy efficient?
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| A.1 |
Look for the Energy Factor (EF) number on the yellow Energy Guide label. It should be .91 or greater. The EF represents the percentage of the energy you put into a water heater that you get back in the form of useable hot water. For example, a water heater with a .91 EF gives you about 91% of the electric energy it uses back in hat water.
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| Q.2 |
Do "tankless" water heaters save a lot of energy?
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A.2 |
Tankless hot water heaters, which are also sometimes called "demand" water heaters, heat water instantly as a household needs it when they turn on a tap. As a consequence this type of water heater doesn't need a storage tank.
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| |
This kind of water heater can save energy because it doesn't have to keep 50 gallons of water hot all the time. Unfortunately, this energy saving comes at the cost of a much greater power demand. For a whole house unit the demand would be about four times that of a storage tank type water heater.
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| |
Besides companies trying to sell demand water heaters tend to overstate the energy savings potential of these units. The total annual standby loss (the energy lost from the storage tank to the environment) of an energy-efficient water heater is only about 300 kWh or about $16. This is substantially less than the thousands of kWh sellers claim.
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Q.3 |
Could my water heater explode like the one
in Burien, Washington?
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A.3
|
Very few water heaters blow up these days. That’s a big part of why the July 28, 2001 explosion in Burien made the news. Very few water heaters blow up these days because they have a virtually foolproof safety valve called the temperature and pressure relief valve (T&P). The T&P releases excess pressure from the tank should other parts of it malfunction. The T&P had been disabled on the tank that exploded in Burien thus making the explosion possible.
The lesson here is to always make sure you have a temperature and pressure relief valve properly installed on your hot water heater.
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Q.4
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Recently I heard about a timer for an electric water heater that turns it off during parts of the day and only turns it on when one expects to use hot water like in the morning when I’m showering and getting ready to leave for work. Do these timers save much energy?
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A.4 |
Adding a timer to your water heater will definitely save energy, but it won’t save very much energy. We figure the economic bottom line is as follows: you can expect to save about $6 per year for a device that will cost you about $35 to buy and about $65 to have installed by a professional.
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Q.5
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Is it really cheaper to take a shower than a bath?
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A.5
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How much does it cost to take a shower?
(assuming a 2.5 gallons-per-minute showerhead)
| |
Shower
|
Bath
|
| time (minutes) |
5 |
10 |
15 |
20 |
N/A |
| water use (gallons) |
12.5 |
25 |
37.5 |
50 |
60 |
| heat used (BTU's) |
5500 |
11000 |
16500 |
22000 |
26400 |
| heat used (kWh's) |
1.61 |
3.22 |
4.83 |
6.44 |
7.73 |
| electricity cost |
$0.14 |
$0.28 |
$0.41 |
$0.55 |
$0.66 |
| water cost |
$0.05 |
$0.11 |
$0.16 |
$0.21 |
$0.26 |
| wastewater cost |
$0.09 |
$0.18 |
$0.28 |
$0.37 |
$0.44 |
| total cost |
$0.28 |
$0.57 |
$0.85 |
$1.14 |
$1.36 |
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