Since I teach this subject, it seemed appropriate to have a page (or ten) on the subject:
The hyper-linked terms below are quick links to the Terminology page. If you're unsure of a term, and it's hyper linked...just click on it for an explanation. If there's a term used, and I haven't hyperlinked it and/or detailed it in the Terminology page, please e-mail me, I'll link it or create a definition.
Heating and cooling your home uses more energy and drains more energy dollars than any other system in your home. Typically, 44% of your utility bill goes for heating and cooling. What's more, heating and cooling systems in the United States together emit over a half billion tons of carbon dioxide into the atmosphere each year, adding to global warming. They also generate about 24% of the nation's sulfur dioxide and 12% of the nitrogen oxides, the chief ingredients in acid rain.
No
matter what kind of heating, ventilation, and air-conditioning system you have
in your house, you can save money and increase comfort by properly maintaining
and upgrading your equipment. But remember, an energy-efficient furnace alone
will not have as great an impact on your energy bills as using the whole-house
approach. By combining proper equipment maintenance and upgrades with
appropriate insulation, weatherization, and thermostat settings, you can cut
your energy bills and your pollution output in half.
Room Air
Conditioners Narration
by Bill Richardson, Secretary of Energy 
It might surprise you to know that buying a bigger room air-conditioning unit won't necessarily make you feel more comfortable during the hot summer months. In fact, a room air conditioner that's too big for the area it is supposed to cool will perform less efficiently and less effectively than a smaller, properly sized unit. This is because room units work better if they run for relatively long periods of time than if they are continually, switching off and on. Longer run times allow air conditioners to maintain a more constant room temperature.
Sizing
is equally important for central air-conditioning systems, which need to be
sized by professionals.
If you have a central air system in your home, set the fan to shut off at the
same time as the cooling unit (compressor). In other words, don't use the
system's central fan to provide circulation, but instead use circulating fans in
individual rooms.
The shopping guide in the back of this booklet will help you find the right size unit for your needs. Look for the ENERGY STARŪ and EnergyGuide labels.
Gas and Oil Heating Systems
If you plan to buy a new heating system, ask your local utility or state energy office for information about the latest technologies available to consumers. They can advise you about more efficient systems on the market today. For example, many newer models incorporate designs for burners and heat exchangers that result in higher efficiencies during operation and reduce heat loss when the equipment is off. Check the Shopping Guide under Major Appliances for additional information on how to understand heating system ratings.
Look for the ENERGY STARŪ and EnergyGuide labels.
If you're having trouble seeing the animation below...get the free Shockwave player...here.
Although
there are several different types of fuels available to heat
our homes, well over 1/2 of us use natural gas.