I've heard some pretty outrageous claims from window replacement companies. The most common 'hook' for selling replacement windows is that you'll get a Return On Investment (ROI) because of all the money you'll save on your heating bills. In the real world, the idea that you could ever come close to breaking even on your investment for new windows is impossible at best, and borders on downright dishonesty. Unfortunately, a lot of consumers believe the window company's claims - I hear this myth repeated many times while doing home inspections throughout Minnesota.
To prove this, I decided to figure out how much money I would need to save every year if I just wanted to break even on the investment of new windows at my house, assuming the windows could last thirty years... although the average life expectancy for replacement windows is actually twenty years. I've already replaced nine of the twenty-two windows in my house with newer energy-efficient windows. If I replaced the remaining thirteen windows with incredibly energy efficient windows and I only paid $500 each, I would have to save 46% on my heating bills every year for the next 30 years just to break even!
I arrived at this number by pouring over my gas bills for the last six years, and figured out how much gas I use to heat my house on average every year.
- I use an average of 520 therms per year to heat my house.
- The average cost of gas is $0.90 / therm, which makes the average cost to heat my house every year $468.
A few details about my house:
- Built in 1939, 1500 finished sf, 1 1/2 story.
- 2x4 construction, most walls have about 2" of rock wool insulation. This means the walls are very poorly insulated, so a lot of my heat loss is happening through the walls.
- Basement is completely unfinished and uninsulated.
- Attic / 2nd floor is insulated with about 3" of closed-cell spray foam.
- Thirteen original single pane windows with removable storm windows installed during the winter.
- Nine newer Low-E windows (the kind that are supposed to save energy)
- I keep my house at 72 degrees during the winter, and I use a setback thermostat.
Assuming each new window costs $500, replacing thirteen windows would cost $6500. To save $6500 over a period of 30 years, I would need to save $216 per year on my heating costs, or 46% or my average annual cost, which is $468. In reality, I might end up saving somewhere around 5%. I've already replaced almost half the windows on my house, and I haven't noticed any significant savings on my heating bills.
I'm not writing this to discourage anyone from replacing their windows - I love new windows, and I dislike my old windows with a passion. They're a huge pane to maintain, and I'm slowly replacing them... but every time I replace a window, I do it because I like having new windows, not because I think I'm going to save any real money on my heating bill. A $1500 tax credit still wouldn't even get me close.
ps - when it comes time to sell your home, a house with new windows will sell for more money than a house with old windows. Home sellers in the Minneapolis area can expect to recoup about 70% of the cost of new windows.
Reuben Saltzman, Structure Tech Home Inspections