View Full Version : Water heater efficiency?

09-12-2005, 07:29 PM
Hi Everybody,

Well, price for all energy sources is going up.
What would be the more efficient way to run water heater?
1. Decrease hot water temperature to acceptable minimum.
Assuming recovery time is also acceptable and heater will
be able to provide enough hot enough water.
This way heat loss will be minimal during the time when
there is no water use at all (most of the day time, except for
weekends and holidays and night time) but heater will be
running all the time when water is actually used.
2. Increase hot water temperature to the allowed limit.
In this case temperature control mixing valve must be installed.
This approach will minimize hot water usage and heater run time
should be less (I am not sure about this?) but heat loss will
be higher due to the grater temperature difference.

Theoretically (in ideal world without losses) there will not be any
difference at all. But in our real life it must be a difference.

What do you think?

Thank you,

- Vitaliy

Dunbar Plumbing
09-12-2005, 08:01 PM
Take shorter showers, less baths, use a water heater blanket to minimize heat loss and insulate the first 8 feet of the incoming cold, the entire hot side water lines. Wash hands with cold water instead of warm. You lose a great deal of temperature loss running water till it gets comfortable.

09-13-2005, 09:29 AM
... and check out tankless/instantaneous water heaters... you only heat what you are actually using rather than storing and maintaining your heated water every hour of every day, year after year.

09-13-2005, 10:56 AM
Hi Guys,

Well, you missed my point.
I am very happy with my current indirect water heater
and I am not going to replace it. Heater itself and all
related pipes are very well insulated.
My question was:
What is more efficient way to run this heater:
i.e. temperature setting should be as low as possible
or as high as possible?

Thank you,

- Vitaliy

master plumber mark
09-13-2005, 03:48 PM
probably the best setting for one is
low to med whichever you find comfortable...

another suggestion is to install shower restrictors
to slow the flow down....

everything else sounds like it has
been covered already by others.

09-13-2005, 05:07 PM
Hi Mark,

Thank you for the answer.
This is actually my current setting and this is what I expected too.

- Vitaliy

09-13-2005, 05:16 PM
Besides efficiency you should consider functionality. If the heater is set at 110, for example, you would use only hot water for a shower, which would give you about 15 gallons of water before it started cooling off, and there would be no way to increase the temperature back to a comfortable setting. Set at 130 degrees, you would mix a considerable amount of cold water with it to attain 110 degrees, so that same shower with the same flow from the shower head will now give you 25 or more gallons of showering water, and when it starts to cool down, you can reduce the cold water to maintain the temperature for a longer period. If you feel the exterior of a water heater you will realize that it is relatively cool, so it is not losing temperature at a "wholesale" rate.

09-13-2005, 05:28 PM
One indirect tank I looked at was speced at 1 degree per hour standby loss at "normal" ambient room temperatures. If it held 40 gallons, that's about 320 pounds or about 320 btu/hour standby loss. Say your boiler is 75% efficient (low by today's standards), you'd need 400 btu to reheat that water to the set point (probably wouldn't happen until it got much lower, though). Not much at all.

09-13-2005, 06:28 PM
Hi Guys,

My heating system consist of Burnhum V73 oil fired boiler
(1.05GPH, 121MBH, 82.2%AFUE) and 40 gallons indirect
Superstore water heater with 1/2F/H temperature drop.
Thermostat is located in the middle (by height) and set to 150F.
At the hot water outlet temperature must be higher but I donít
know by how much. System is running very well. Boiler fires
once a day (occasionally twice) and runs about 20min. We are
very comfortable to use two showers simultaneously.
Each shower has pressure balanced faucet so flushing toilets
does not create temperature discomfort.
Looks like my system is very well tuned.
Should I try to lower temperature to 130F as HJ suggested
or it is better not to touch things at all and leave it ďas isĒ?

Thank you,

- Vitaliy

master plumber mark
09-14-2005, 05:58 AM
if it is working good and everything is
well tuned,

especially with the "more special system" you got

I would say leave it alone unless you are

really into abuseing yourself...