(Joe Doe) wrote in message >...
> I do not believe everything CR says. Their interpretation is one
> interpretation (and could be a contributing factor). In general I doubt
> their competence. For example they assume that the manufacturers quoted
> 9000 BTU is OUTPUT BTU. This is guaranteed not to be true. If it were
> true, water would boil faster than their quoted figures. So even though
> they are supposed to be semi-competent they make mistakes as laughable as
> this. So while I think they can put a pot of water on a stove and measure
> the time it takes to boil that is about all I think they can do. They
> also slam some burners because they cannot maintain a simmer. This is
> laughable to any competent cook - simply add a flame diffuser. While it
> is desirable in terms of energy efficiency to match a burner to a task, it
> is silly to create a non-existent problem (simmer function) and by the
> power of their bully pulpit cause manufacturers to make a less versatile
> burner.
>
> In support of my original point that burner efficiencies are important see:
>
> http://www.epri.com/journal/details....ctype=features
>
> This is an article by the electrical power research institute pushing an
> induction burner but it shows that commercial gas burners only have 30%
> efficiency and residential 47%. Scroll to about the bottom third of the
> article to find a bar graph showing the efficiencies. This is also
> repeated in the text of the article where they say: "The Luxine unit had
> a energy efficiency of 92%, compared to 72% for the radiant electric
> range, 47% for the residential gas range, and 30% for the commercial gas
> range".
>
> This data supports my point nicely - the 20,200 BTU commercial range would
> put out 6060 BTU of heat while the 9500 BTU residential would put out 4465
> BTU. So the difference between the commercial and residential is 35%
> instead of the naive expectation of a >100% difference. The consumer
> reports article I was thinking of, had a GE profile with a 12,500 BTU
> burner beating a DCS with a 15,000 BTU burner. To me efficiency seems the
> most likely reason why the DCS performed poorly.
>
> I have come across these kinds of figures in other searches (research done
> mainly by utility companies promoting energy efficiency) wrt to commercial
> burners so I believe it. More efficient commercial burners exist, but as
> I pointed out you actually need to know the efficiency of the burner under
> consideration to make meaningful comparisons between lines. Since this
> seems to never make it out in the specification sheets, we can only guess.
>
> Incidentally gas furnace manufacturers are more forthcoming - they
> frequently cite Input BTU, Output BTU and Efficiency
>
> Roland

Roland, thanks for the link to the very informative article. I'd just
like to point out that the EPRI article talks about "cooking
efficiency". That's a little different than "efficiency" in the sense
if input and output BTU's. Unlike, for example, a furnace where you
have so many BTU's input and so much hot air coming out and input and
output BTU's are different, every burner that completely burns gas
(i.e., doesn't leave significant unburned hydrocarbons or produce
carbon monoxide - in other words all burners, we hope) is by
definition 100% efficient. In other words, input and output BTU's are
the same for any burner. If you burn a certain volume of natural gas
or LPG, you get a certain amount of heat. Period.

The question is whether the heat makes it in the pan or not - *that's*
what the EPRI article is talking about when they use the term "cooking
efficiency. " Electric "burners" whether induction or even ordinary
ribbon elements excel at this because the close contact to the pan;
most heat ends up in the pan and little in the room. Gas burners are
obviously quite different - you need room for the flame, heated air
runs up the sides of the pan and you actually get more heat in the
room than into the pan.

Anyway, that's why you don't see numbers like input versus output BTUs
or efficiency for cooktops - the former are always the same and the
latter is always 100%. It's not that cooktop manufacturers are less
"forthcoming" than furnace manufacturers. It would be nice if what
the EPRI article calls "cooking efficiency" but of course that is
highly dependent things like on size of the pan that are some degree
out of the manufacturer's control.

- Mark W.