On 30-Mar-2004, wrote:

| So regardless of the voltage, amps, wattage, size or shape of the heating
| element, as long as the heater is able to supply enough energy to match the
| loss (76 watts in my case), the total energy used over a long period will
be
| the same; but the duty cycle will change. You could put a 76 watt heater
| inside the tank, and it would use the same long-term energy as a 4500 watt
| heater. It would just have a longer duty cycle -- 100% rather than 1.6%.

But you're still losing 76 watts of energy. The question is, is there a
way to recover that cheaply. In cold weather, if you could recover 100%
thay would be 76 watts less (or equivalent) energy used for other purposes.

Yes, that is correct. I suggest extra insulating blankets around the heater.
That might cut the heat loss in half and reduce the average energy usage to 37
watts which would save about $2/month.

Also, how much would these figures change if you put the water heater on a
timer to ensure that it only heated during night?

Timers that turn off the water heater for a few hours are virtually useless
because nearly all of that energy is put back in to reheat the water when the
timer turns back on. Now, if you're going to be away for a week or month, you
might save a little money because the tank will have time to cool down and stop
losing energy through the insulation. But the temperature drop over a 6 hour
period is only a few degrees, so the reduction in heat transfer through the
tank due to that small drop is practically insignificant. When the timer turns
on, the heating element runs continuously for many minutes to bring the entire
mass of water back up to the set temperature, and that energy will nearly equal
the energy "saved" during the time that the heater was turned off.

If you are going to try to increase the efficiency of a hot water heater, it is
better to use an insulating jacket than a timer. But regardless of what you
do, you won't save more than $4/month unless you either (1) reduce your hot
water usage or (2) change to a cheaper source of energy (gas, heat pump, solar,
etc.).