So today I was talking to mom on AIM, and she said that we won't be keeping the house any warmer than 64° F this year because she can't afford it. I immidiately thought, "HOW STUPID!". If you've ever taken a physics class, you know exactly WHY it is stupid.

Everything in the world has what's called a "specific heat", which Google defines as "The quantity of heat required to raise the temperature of a unit weight of a substance by one degree". As you can probably guess, this quantity of heat is a lot higher for some substances as it is for others. For example, water has the highest specific heat of anything on Earth. You can see this by boiling a pan of water. It takes a certain amount of time to heat the pan of water to 212°F (100°C), and the water holds its heat for a certain amount of time thereafter. If you've ever had to simmer something, you know that you have to heat the water up with a high flame, then lower the flame so you can keep the water at the temperature you desire without getting hotter or colder.

Think of your house this same way. While a house doesn't have the same specific heat as a pan of water, it is very similar in how it behaves. If it is 20°F outside and you want to heat your house to 64°F, you will have to let your furnace run for a certain amount of time to get the temperature to 64°. After that, you will keep your thermostat on 64°F and the furnace will run only once in a while to maintain the temperature. Raising the temperature doesn't change how much the furnace will run to maintain the temperature; it just changes how long it will initially run to raise the temperature to that point.

So what am I saying? It isn't any different to keep the thermostat on 64°F than it is to keep it on 70°F when it comes to the amount of fuel used to hold the temperature.