bpnjensen wrote:

In the winter, this is probably true - what you lose on light
efficiency you save on heating. Then, the question becomes - per unit
of tangible heat energy, what costs less - the electricity to light
the bulb or the "other" source?

The most efficent way to heat is by moving heat, not creating it.
A refrigerator works by moving heat out of the cooling compartment into
the room. This is a specific case of a heat pump.

An air conditioner is a similar case. Some air conditioners can be run
backwards, i.e. used to suck heat out of the air and deliver to a room.
These are called in the US "heat pumps", which is silly as an air conditoner
of any kind is a heat pump.

Here they have hit the market big, with a large reduction (almost to
nothing, VAT only) on airconditioners, there is a big influx of models
and lots of competition. They are called "inverters" here.

The next most efficent way of heating is fire. Either radiated heat from a
fire, or transfered heat via pumped air or water. My son just moved into a
new apartment and it has a Junkers (German) gas heater. The heat transfer is
so efficent, the case and exhaust pipe are plastic. It's smaller than a
a microwave oven, interior wall mounted and heats a 150 square meter apartment.

A neighbor has a 20 year old Junkers, and it is a huge metal box the size
of a medium sized refrigerator, mounted on an outside wall with a metal
vent pipe. My guess is that most of the heat gets radiated by the box and
vent pipe and goes up the chimney as it were.

The technology has improved immensely.

A fireplace is the exception to the rule because since it is in a room
with people it needs to be properly ventilated and more heat goes up the
chimney than into the room. Add into it the fact that the room requires
a constant flow of fresh (outside) air, which is cold and you get very
close to a net loss.

A stove is better as you can control the amount of air in (and therefore out),
but not a lot.

Electric resistance heating is really poor, not only does it give you
so little heat per kWh, electricity is expensive. The average kilowatt
hour in the US at your home starts out as 3kWh at the generating plant.
Since more than half of the electricity in the US comes from coal,
and most of the rest from oil, think about it.

I always laugh because people here buy these sauna heating panels. They
are about a foot square and consume/output 400 watts of heat. This means
if they are on full they reach over 120F, which makes them impossible to
put anywhere near people. If you turn them down to a safe and comfortable
temperature, they consume less electricity, but put out less heat. They
also are less efficent at the lower temperatures.

So the answer is if you live in a climate that does not drop below
freezing an electric heat pump (backwards air conditioner) is probably
your best "bang for the buck". Probably you could get away with
electric auxilary heating for the few days it becomes so cold that
the heat pump can't suck enough heat out of the air.

If you live in a colder environment, then you probably would need an
auxilary heater such as a Junkers or the US equivalent.

Then there is the whole notion of solar heat collectors. There are special
ones designed to keep GPS satellites warm and can reach 250F from "earthshine".
A former co-worker was going to install them in the UK, I never did hear if
he did and if so, how they worked out.

Note that heat and electricity storage systems are expensive and not always
practical, so any solar heating system needs a backup.

With that said, we have a solar hot water heater and it does enough heat
for 3-4 showers at night May through September. It does not see the sun
until 11am, so if you want a hot shower in the morning you have to use
an electric heater.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.
i.e possessing less facts or information than can be found in the Wikipedia.