Home Page link

What does BTUH rating mean on water heaters?

Home| Search | About
Login Password
Register Now! Lost Password?

Home Repair - - If it ain't broken, don't fix it. Otherwise look here. 

Bookmark this page:  YahooMyWeb Yahoo!  Google Google  Windows Live Favorites Windows Live  del.icio.us del.icio.us  digg digg  Add to Netscape Netscape
Subject Author Date
What does BTUH rating mean on water heaters? DesignGuy 07-11-2006
If you were  Registered and logged in, you could reply and use other advanced thread options
Posted by DesignGuy on July 11, 2006, 1:47 pm
I'm getting ready to replace my Rheem 75 gallon gas water heater with a
Kenmore Power Miser of the same size.

However I noticed that the Rheem has a rating of 75500 input BTUH, and the
Kenmore has rating of 55000. I'm not clear if a loer or higher number is
better, as some explanations I've read seem to indicate that the Rheem would
use more BTU's to heat the water than the Kenmore (thereby making the
Kenmore more efficient).

Is my reasoning correct or is the reverse actually true?

Thanks in advance.




Posted by dpb on July 11, 2006, 2:10 pm

DesignGuy wrote:
> I'm getting ready to replace my Rheem 75 gallon gas water heater with a
> Kenmore Power Miser of the same size.
>
> However I noticed that the Rheem has a rating of 75500 input BTUH, and the
> Kenmore has rating of 55000. I'm not clear if a loer or higher number is
> better, as some explanations I've read seem to indicate that the Rheem would
> use more BTU's to heat the water than the Kenmore (thereby making the
> Kenmore more efficient).
>
> Is my reasoning correct or is the reverse actually true?
...

No and no...that rating is related to the "first hour rating" and
correlates to how fast it will heat cold water initially. The higher
the input, the faster the water will get hot (and reheat when
recharged).

The overall energy efficiency is the energy factor (EF) and comprises
recovery efficiency and standby and cycling losses.

See (watch wrap)
http://www.eere.energy.gov/consumer/your_home/water_heating/index.cfm/mytopic=12980

for an overview. There's a rating on each unit that compares operaing
costs that correlates (roughly) to efficiency but that's not the only
criterion in making a selection.

for


Posted by Wayne Whitney on July 11, 2006, 2:11 pm

> However I noticed that the Rheem has a rating of 75500 input BTUH, and the
> Kenmore has rating of 55000. I'm not clear if a lower or higher number is
> better, as some explanations I've read seem to indicate that the Rheem would
> use more BTU's to heat the water than the Kenmore (thereby making the
> Kenmore more efficient).
>
> Is my reasoning correct or is the reverse actually true?

The reverse is probably true. The BTUH rating doesn't tell you
anthing about efficiency, it just tells you the rate at which the unit
can draw and burn gas. If the units are of comparable construction,
they likely have comparable efficiencies. In this case, the higher
BTUH unit will simply reheat its hot water tank faster after hot water
is drawn out of it.

For efficiency, look at the water heater's "ER" rating. This will be
a number between 0 and 1 that basically tells you how much of the
theoretical energy available in the gas the water heater burns
actually makes it into heating the water. It reflects inefficiences
in the burner itself as well as standby losses from the storage tank.

Cheers, Wayne


Posted by Keith Williams on July 11, 2006, 2:20 pm
dontbother@nowhere.com says...
> I'm getting ready to replace my Rheem 75 gallon gas water heater with a
> Kenmore Power Miser of the same size.
>
> However I noticed that the Rheem has a rating of 75500 input BTUH, and the
> Kenmore has rating of 55000. I'm not clear if a loer or higher number is
> better, as some explanations I've read seem to indicate that the Rheem would
> use more BTU's to heat the water than the Kenmore (thereby making the
> Kenmore more efficient).
>
> Is my reasoning correct or is the reverse actually true?
>
BTUH == BTU per Hour. A BTU (British Thermal Unit) is the heat
needed to raise a pound (pint) of water from 39.1F to 40.1F (love
them English units! ;). A BTUH is then the total number of
pints*degrees it'll raise the temperature of the water per hour.

The Kenmore unit will take about 40% longer to raise the water to
temperature than the Rheem. During that time they'll take exactly
the same energy (ignoring insulation losses). If they had the same
insulation (unknown) the cost to run would be very nearly the same
but the Rheem would have a 40% faster recovery.

--
Keith

Posted by DesignGuy on July 12, 2006, 11:19 am

> I'm getting ready to replace my Rheem 75 gallon gas water heater with a
> Kenmore Power Miser of the same size.
>
> However I noticed that the Rheem has a rating of 75500 input BTUH, and the
> Kenmore has rating of 55000. I'm not clear if a loer or higher number is
> better, as some explanations I've read seem to indicate that the Rheem
would
> use more BTU's to heat the water than the Kenmore (thereby making the
> Kenmore more efficient).
>
> Is my reasoning correct or is the reverse actually true?
>
> Thanks in advance.

Thanks guys, that makes it clear.




Similar ThreadsPosted
Hard water & Indirect Water Heaters June 8, 2007, 11:29 pm
Water Heaters... November 6, 2005, 10:48 am
two water heaters December 14, 2005, 3:13 pm
GAS HOT WATER HEATERS February 18, 2006, 1:16 pm
Gas water heaters May 26, 2006, 10:04 am
gas water heaters June 15, 2006, 1:15 pm
Water heaters September 7, 2007, 4:17 pm
Thin Water Heaters July 18, 2005, 9:23 am
Tankless water heaters September 8, 2005, 1:47 pm
Recommendations for gas water heaters? January 12, 2006, 9:56 pm

Contact Us | Privacy Policy

XML SitemapXML Sitemap