In article . com,
says...

Mike Hartigan wrote:
I recently had a discussion with a friend who recently replaced his
kitchen range. He said that he didn't even consider natural gas
because the price has taken a dramatic jump in the past year, making
electric cooking much cheaper. His perception of the relative cost
may or may not be true - I don't know (although I suspect that NG is
and will continue to be more economical for the foreseeable future).

The discussion went off on a tangent regarding the efficiency of a
gas range vs a gas furnace. Given that gas burners heat the kitchen,
they obviously take some of the load off of the furnace (cooking
during the heating season is assumed here). But an intriguing
thought occurred to me - since the range is not vented to the outside
like the furnace is, all of the heat generated by the burning gas
remains in the house. This means that the more you cook, the lower
your gas bill should be, even with un ultra high efficiency furnace.
Is this true? Should I encourage my wife to bake more cookies for
the purpose of saving energy? Can it be that simple?

Granted, there's a downside to heating your home with the kitchen
range. But is my speculation valid?

Yeah, it seems to me that's correct, but you are leaving out the
question of combustion efficiency; i.e., if the furnace burned 90% of
the gas but the stove only burned 80% or something like that. I have no
idea if there is any difference, I hasten to add, just being
theoretical.

Given that there is no heat escaping through a chimney, I believe
that the stove would, in this context, be 100% efficient.

Speaking of which; given that a light bulb is inefficient because so
much of the electricity goes off into heat..... would an electric
heater be nearly 100% efficient because it gives off so little light?
Just wondering where else the energy could possibly go.

Electric heat is 100% efficient. Indeed, an incandescent light bulb
is also 100% efficient. Unfortunately, most of the energy is given
off as heat rather than light. But 100% of the energy is converted
into a useable form - heat and light. If you heat your home with
electricity, then the efficiency of your light bulbs is irrelevant.
Save your money and leave the CF bulbs for the natural gas users!