Good Question - Can lowering your thermostat at night really save you money? How much?

by | Dec 16, 2010 01:08 PM ET

Right now in the United States we are in the grip of a very cold winter. Heating the house is going to be expensive with this kind of weather going on. What if you want to save money? One option, especially if you have an older home, is to do things like adding insulation:

I have an old house with bad insulation. Will new insulation really save money?

But that is not a small project. Is there anything you could do, immediately, at low cost, to cut the heating bill?

The easiest thing to do would be to turn down the thermostat. It will definitely save you money, but how much?

If you read How Insulation works, you can see that the goal of insulation is to slow down the flow of heat through walls, ceilings and floors. The amount of heat that makes it through the insulation depends on the temperature difference. So if the difference between indoor and outdoor temperatures is 40 degrees F, some amount of heat will leave your house. if the difference is only 20 degrees F, the amount of heat loss is cut in half. That means your energy cost gets cut in half too.

Let's say that you typically set your thermostat at 70 degrees F, and the outside temperature is 30 degrees F. You decide to take the radical step of turning your thermostat down to 50 degrees F at night and piling on a couple more blankets while you are in bed. Let's say you keep the thermostat at that low setting for 8 hours every night. How much money could you save?

On this page we calculated the heat loss for a well-insulated 2,000 square foot home with a 40 degree F temperature difference to be 16,400 BTUs. By setting the thermostat to 50 degrees F, it saves 8,200 BTUs, or 2,410 watts. Over 8 hours, assuming you heat with electricity, that works out to about 19 kilowatt-hours, or $1.90 per day if electricity is a dime per kilowatt-hour. Over the course of 100 days, you save close to $200. That is a tangible amount of money. If you are able to do the same thing while you are at work, you save even more. If you have a poorly insulated old house you could save a lot more.

You can use a programmable thermostat to do the changes, or simply turn it down yourself if you don't want to blow the money:

There is one thing to keep in mind if you try this, especially in an old house. You have to think about the pipes. Let's say you turn the furnace completely off at night. If the house gets cold enough, the pipes will freeze. Pipes in exterior walls (for example, the kitchen sink) are especially vulnerable. If you lower the thermostat a lot, it may be a good idea to open the cabinet doors under the sink to keep the pipes warm.

See also:

- I have an old house with bad insulation. Will new insulation really save money?

- How Insulation works

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