For example, changing windows is expensive and costs $133.88 per ton of carbon saved; changing to a programmable thermostat is cheap and comes in at $ 9.34 per ton of carbon saved. So before the vinyl window salesman tells you to fix your windows, do all of the cheap and effective stuff first. second- do all the free and effective stuff first:

Free Stuff:

1. Lower water heater temperature to 120°F
2. Lower AC thermostat by 3°F- greendailygrind comment: by lowering your thermostat by just 1 degree, you will save 3% in home energy costs. 2 degrees saves 2,000 pounds of CO2 emissions over the course of a year!
3. Wash clothes in cold water
4. Air dry clothes during summer
5. Turn off unneeded lights

Just doing that will save 1600 tons of carbon and $250 per year.

6. Get a Programmable Thermostat: $9.34 per ton CO2 saved

a setback, or programmable thermostat has the biggest bang for the buck of any single thing you can do; it costs only $9.34 per ton of carbon saved, and is getting better all the time as the price of the electronics drop. A setback thermostat can save up to 15 percent on your heating bill.

For houses with radiant floors or old hot water radiator systems, there is a really slow response time because of the thermal inertia in the systems. I used to say that setbacks wouldn’t work for these, but new thermostats track the performance of your heating system, figure out when to turn it on, and basically plan ahead. After all, nothing makes you want to jump under the covers than a cool house before you go to bed!::More

7. Stop the Air Leaks: $10.77 per ton CO2 saved

Next up on the RMI Guide is to seal large air leaks, cheap to do (mostly labor, minimal materials), costing a mere $ 10.77 per ton of carbon saved. In an old, pre-1945 house, the air leaks can add up to the equivalent of a hole in your wall 21 inches in diameter! Natural Resources Canada (NRC) says that in a house vintage 1946-80 the hole is 16 inches, and in a modern conventional home, 14 inches. When you think about it that way it becomes obvious that there is a lot of heat loss, it is like leaving a window open all winter. ::More

8. Insulate Your Water Heater: $12.66 per ton CO2 Saved

Here we have a really easy one, that costs only $ 12.66 for every ton of carbon saved. You can buy kits at hardware stores or the big boxes like Home Depot or Lowes, that come with straightforward instructions. ::More

9. Add Attic Insulation: $ 15.56 per ton CO2 Saved

Many houses have attics that are accessible via a hatch in the hall or a cupboard; if you have this, insulating your attic is not that hard, and delivers a good bang for the buck; RMI estimates it will save you 2,142 pounds of CO2 per year, at a cost of $15.56 per ton. We think R-50, or about 16″ of glass fiber insulation is a good target. Glass fibre is cheap, relatively easy to install, and noncombustible, so we will look at that first but it is not your only option. ::More

10. Install Efficient Showerheads: $18.02 per ton of CO2 Saved

Almost as easy as wrapping your water heater, changing your shower head costs only $18.02 for every ton of carbon dioxide saved, and saves you $21 per year. The U.S. Environmental Protection Agency (EPA) notes that showers use about 17 percent of residential water use, totaling 1.2 trillion gallons per year. ::More

11. Weatherize Your Windows: $25.02 per ton of CO2 Saved

If you live in the north in a drafty old house, this is an important one. The window salesman may tell you that you have to replace those old wood windows, but they are often part of the character and charm of the house, the replacements are usually vinyl, and it costs a lot of money.

RMI suggests that weatherizing your old windows will save 621 pounds of carbon at a cost per ton saved of $25.02; I suspect it is much more money saved than that. These instructions are for double-hung windows, but they work for most kinds. The products I use are a seal and peel caulk (wonderful stuff; no matter how bad you are at caulking it just peels off in the spring) and heat-shrinking film. I lust after magnetic interior storms but that is more expensive. ::More

12. Install Faucet Aerators: $27.27 per ton of CO2 Saved

After spending the weekend winterizing our windows, next up on the RMI list is dead easy by comparison and cheap too; saving $6.22 and 110 pounds of carbon, at a cost per ton saved of $27.27. I am frankly surprised that such a little step does this much at all, but by mixing air with water you use less water and that means less water heating.::More

On a bang-for-your buck basis, it all goes up from there.

It doesn’t mean you shouldn’t do them; some are cheap (like cutting phantom power loads in half, costing $128 per ton but cheap to do) and some are really expensive and not that effective (like adding low-e films to existing windows, topping the list at $241 per ton of CO2 saved). It is not always intuitive, but it is useful if you are trying to live a frugal green life.