Quote:
Originally Posted by RainyRainyDay
I'm no expert, but I think most gas furnaces don't work when the electricity is out, because some parts of the system are electrically driven.
Historically, natural gas has been much cheaper than electricity for home heating, hot water and clothes drying. Maybe that's changed lately, but I'm really surprised at the claim that electricity is apt to be waaay cheaper in the long run. Really?
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In a word, no. With a major caveat.
First off, a gas furnace is cheaper to run than an electric furnace. In fact, I would personally install a bottled propane system before an electric burner system.
The simplified theoretical underpinning is easy to see. Say the electric plant burns gas. (It might burn coal or even fuel oil, but in practice this doesn't matter.) If you burn gas in your furnace, you get 100% of the heat. If you change the heat into electricity, transmit it 30 miles, then reconvert it to heat, you lose a lot of the energy in the process.
Here's the big caveat: Since we (Atlantans) are in an area of high air-conditioning use, a more expensive "heat pump" becomes a consideration. The technology is extremely different for heating with a heat pump and using a furnace. A heat pump basically air conditions the air outside and heats the house with what would be considered the "exhaust" (but don't worry, it is perfectly clean -- there is no relationship to, say, car exhaust).
A heat pump is
extremely efficient when the difference between the air outside and the desired temperature inside (called the "lift") is comparatively small. This can get very complicated. If you are using a heat pump, electricity is cheaper is when the outside temperature is above what is called the "balance point", about 45-55 degrees, or even less with a great (i.e. expensive) heat pump. The number depends on several factors, such as how warm you want your house to be and how good the heat pump is.
IMHO, the "best" system considering fuel cost and performance (with a nod to the environment) is a dual system including a good heat pump and a multi-speed gas furnace The heat pump provides air conditioning and also provides heat when the outside temperature is above something like 45 degrees F, at which point the gas furnace cuts on.
The amount of furnace and heat pump usage is extremely complex and is run by a computer chip. (The gas furnace should have more than one "stage"; like a two-stage furnace might turn on the main burner at 45 and have an auxiliary burner setting when the house is very cold, to speed up the warming process, or when the outside temperature is very cold.)
That said, you
could use a heat pump without any furnace at all to heat your home in Atlanta, but I wouldn't advise it. I don't know if fuel would be more or less expensive in an average year using only a heat pump for heat, but I do know that the house would not be acceptably heated on cold days. Not to mention, it would have to run all the time but at low outside temperatures it would be prone to icing up and have to be turned off for a while; it would then take a very long time to reheat the house.
(A heat pump will warm a house, with steadily decreasing fuel efficiency, to the point where the outside temperature is about 20 degrees. You could theoretically go even colder depending on insulation and the heat pump quality.)
As long as I am getting long-winded, I'll add that it is possible to have a
geothermal heat pump. Cost-wise, you'd have to be a big environmental supporter to get one, but they are commercially available. (I don't think it would pay for itself unless you lived in an interior desert with major daily heat fluctuation.) Anyway, instead of exchanging heat into the air, these rely on buried pipes to exchange heat with the deep earth. Because the ground stays much warmer in winter and much cooler in the summer compared to the air, a geothermal heat pump is incredibly efficient all year, if you live in an area of seasonal (and/or daily) temperature fluctuation. I'd ballpark energy savings of 75% over a furnace/air-conditioner combo.
Note also that gas burns cleaner than oil and has a better environmental footprint than electricity (unless you get clean electricity, e.g. 100% hydro or nuclear, which you don't in Atlanta).
All the other gas appliances, at least those I can think of, run fine during a power outage. Including, notably, hot water, gas fireplace, and stove, all of which will provide some comfort during a power outage.
A gas furnace will not operate without electricity, which is needed for several fans, the gas valve, and the thermostat. However, the amount of electricity involved is fairly small. So you have two possible backups if it's important to you.
First, an electric generator. This involves some one-time expense for hookup, but you don't need a very large generator to power a furnace. I wouldn't bother in Atlanta, and if you are renting an apartment, this isn't an option anyway.
The other option is to put a gas space heater in one room.
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