Re: Are electric WH timers worth it
- From: Tony <none@xxxxxxxxxxx>
- Date: Wed, 06 Aug 2008 19:22:48 -0700
Jordan wrote:
I just started thinking about getting an electric water heater timer for my 3 year old 30 gallon water heater. I checked some of the reviews for the Intermatic timers and it looks like everybody loves them and they say they practically get their $40 bucks back each month.
Are timers all they seem to be cracked up to be and will turning off the water heater from 10 PM to 8 AM really save a family of 4 a big chunk of change each month?
I believe it is extremely unlikely these folks are really getting their $40 back in savings each month. Firstly, it is nearly impossible to make any sense of one's real energy savings by comparing last month's, or last year's power bill with the current one -- it is just not that accurate, and there are far too many extraneous factors affecting one's energy consumption.
On the other hand, a timer would just about have to save some energy. Let us look at a very short explanation of what happens to energy with regard to a water heater. It is evident that energy goes in and energy goes out, as it does with all things. Since it remains at about the same temperature all the time (as maintained by its thermostat), we know that the energy that goes in must equal the energy that comes out.
The simpler side of the equation is the energy that goes in: Energy is supplied in exactly enough quantity to maintain the water heater at a constant temperature or, in other words, to exactly balance energy that escapes. This energy is purchased from the energy supplier. If one really wanted to measure that energy, one could buy a small watt-hour meter and connect it to the electrical feeder, although the price of doing this may not be worthwhile just for the sake of curiosity.
The other side of the equation is about where the energy goes when it leaves the water heater. There are two place this energy goes: consumption of hot water, and loss through the insulation.
Consumption is ordinarily by far the largest expenditure of heat energy, and the most variable. The energy used is proportional to the amount of water used times the difference in temperature between the hot water and the incoming cold water. Devices such as solar preheaters and graywater heat recovery systems do save energy by increasing the temperature of the incoming water using "free" energy. However these systems have an initial cost and a maintenance cost, which must be subtracted from energy savings. It may take a surprising number of years to make these systems pay for themselves, unless, maybe, you can make and maintain them yourself.
Leaking faucets can wast a surprising amount of water and, if it is hot water, a surprising amount of energy. Fixing leaks should be the first priority.
Loss through the insulation is simpler. The loss is continuous, without regard to how much hot water is used. It is proportional to the difference between the tank water temperature and the surrounding air, or "ambient" temperature, and inversely proportional to the R-value of the insulation around the tank.
By far the simplest way to reduce ambient loss and save energy at the hot water tank is to surround it with a thermal blanket, which is available as a kit at most hardware stores. The claims of savings will be, of course, exaggerated, but these kits don't cost too terribly much, are easy to install, and really do save energy. If your water doesn't have one, it should get one.
Another very effective way to reduce ambient loss is to reduce the temperature of the water heater, thereby reducing the difference between the water temperature and ambient temperature. Generally, anything above about 120F is getting wasteful. 140F will make the hot water last longer at shower time (because it takes less hot mixed with the cold to make a comfortable shower temperature), but if one really wants to save energy and money, one could get by with a shorter shower.
The timer, of course, turns off the electricity supply to the water heater at certain times of the day. While the power is off, the water temperature will gradually decrease toward ambient temperature. When the timer turns on again, the heating element will add energy to bring the temperature back to its normal setpoint. In the time that the timer is off, the tank temperature will be somewhat cooler, and so the difference between tank temperature and ambient will be somewhat less. How much will the tank cool off? That depends upon the insulation, which an energy-conscious owner will have already maximized, and how long the heater is off. In fact the savings, with good insulation and no consumption, will be rather small. Will the timer pay for itself? Yes, eventually. To determine how long that will take, will require looking up the formulas for heat loss and doing an analysis for each individual case. Absolutely do not rely on the claims on the box.
So? Do things in this order to save energy:
1. Take shorter showers, wash full loads of laundry and dishes.
2. Fix leaky faucets, if there are any.
3. Put a blanket around the water heater, including the top.
4. Reduce the temperature setpoint to no higher than 120F
5. Mess with the timer business if you must.
Oh, the answer to your question is: No, not really.
Anthony Straight
tonyelectric.com
** Posted from http://www.teranews.com **
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