On Sun, 10 Feb 2008 22:20:41 -0700, Rick Blaine wrote:
Consider the case where one heater has poor insulation and a very
efficient burner, and the other has a poor burner and better insulation. Both
have the same EF, both cost the same to operate over a year. Which one do you
buy?

Hi Rick,
I don't wish to argue ... just to understand ... so please bear with me.

I've said a lot that is wrong (e.g., I called the EF an "efficiency"
factor) and at first I was choosing by size and warranty (which is about as
opposite of the true selection process as is possible) ... so I'm learning
from all you guys and trying to truly understand how to properly select a
real water heater out of the real selections and choices truly available
today in my area.

It seems like I'm not the only one confused as some people said to buy a
water heater by CAPACITY (which seems nearly meaningless except for overall
mechanical size reasons) instead of by FHR, for example.

The web site you recommended was better for FHR than those I tried:
http://www.eere.energy.gov/consumer/.../mytopic=12990

As that web site CLEARLY said the FHR is the most important VOLUME number.
"To properly size a storage water heater ... use the water heater's first
hour rating (FHR). The first hour rating is the amount of hot water in
gallons the heater can supply per hour (starting with a tank full of hot
water). It depends on the tank capacity, source of heat (burner or
element), and the size of the burner or element."

So, I now know that the volume (e.g., 40 gallon or 50 gallon is a nearly
meaningless number when the actual FHR is known).

But, I'm still confused about the EF.

That same web site:
http://www.eere.energy.gov/consumer/.../mytopic=13000

Says "the energy factor (EF) indicates a water heater's overall energy
efficiency based on the amount of hot water produced per unit of fuel
consumed over a typical day. This includes ... how efficiently the heat
from the energy source is transferred to the water ... the percentage of
heat loss per hour from the stored water compared to the heat content of
the water ... [and] the loss of heat as the water circulates through a
water heater tank, and/or inlet and outlet pipes."

So, if I understand it correctly, all we need is the EF and the FHR and the
actual size (e.g., 40 gallons, 50 gallons, or 60 gallons) is meaningless
from the standpoint of how much hot water it delivers or how much it costs
to operate.

This seems so counterintuitive that no wonder a lot of people are confused,
even me. But then, like countersteering on a bicycle, sometimes you do turn
left to go right.

At the moment, it seems that the actual capacity of the tank is a nearly
meaningless number (except for dimensional reasons) - as is the warranty -
based on that web page (since both the FHR and ER already take into account
the tanks' size).

Donna