Is Rinnai 1004 really 84% AFUE...does it matter?

[pcampbell]

I am trying to find a realistic approach to more a more efficient (and more fun) way of heating our home and I feel like I'm going in circles between a pellet stove, a gas stove and a Rinnai 1004 running on natural gas where I am paying $1.45 per therm (100k btu).

Of the three the Rinnai "seems" to be the most efficient. Rinnai says it's 84% efficient, but I can't find it anywhere on their website where it actually says 84% AFUE (while on other products it does claim AFUE, for the 1004 it just claims "efficient"), even in the installation manual PDF doesn't have steady state efficiency numbers or AFUE numbers that I can find. Based on input BTU vs output BTU is 80%... assuming that would be a steady state number.

With something like that you better hope it is 84% efficient because it's not getting off on it's good looks

Now if I look at a Harman Clarity gas stove I see 71.6% AFUE and 80% stead ystate. Assuming the Rinnai truly is 84% AFUE is it safe to compare that apples to apples for how much heat you will get per therm of natural gas?

Should I forget about AFUE? Is this just some bogus figure anyway?

Obviously I like the looks of a STOVE better than the Rinnai and that counts for something. I am just boggled over here!

 

[pcampbell]

I was surprised to not see any replies to this. It was a tough choice but we ended up going with this unit over a few very beautiful looking stoves due to price and efficiency...It should be installed within a week or so in time for cold season assuming it doesn't stay 65 F the rest of the winter. Does anyone else have one of these and how do you like it?

 

[begreen]

Mostly wood burners here pcampbell. The Rinnai looks like a nice unit. I saw a similar Monitor unit in action. It did the job of space heating pretty well.

AFUE is an important standard. It tells you how efficient the unit will be. Fuel costs will likely go only one direction, so any efficiency investments made now, will accelerate in their return on investment.

"Annual Fuel Utilization Efficiency, a rating that reflects the efficiency of a gas furnace in converting fuel to energy. A rating of 90 means that approximately 90% of the fuel is utilized to provide warmth to your home, while the remaining 10% escapes as exhaust."
(broken link removed to http://www.ahservice.com/glossary.html)