Can I save money by getting a window air conditioner and using my central air less? August 8, 2012   Subscribe Will turning up the thermostat on my central air and buying a window AC unit for the one room I use the most make a significant difference in my electric bill? This is hopefully a simple question, but I'm not confident that my assumptions are correct. I recently bought a house, it's a 2-story that's about 1750 square feet, located in Michigan USA. The house has a central air unit that looks very very old, but still functions well. The thermostat in the house is on the ground floor, and I've kept it set to about 70 degrees Fahrenheit when I'm home, since the upper floor tends to be at least 7-8 degrees warmer than the ground floor, and I spend more of my time upstairs. I am currently the only person living here. The outside temperatures during July were generally in the 90s, occasionally in the 100s. I knew that cooling a 1750 square foot house was going to cost more than cooling my old 1-bedroom apartment.

But I was surprised by just how much more. My electric bill last month was $260, twice the highest amount I ever paid while living in an apartment! I'm guessing that the AC is the main difference between the bills at these two places, since everything else I own is more or less the same, and is getting the same amount of use (same computers and TVs, comparable refrigerator, etc). I'm trying to figure out how to save money on my electric bill while at the same time cooling my upstairs bedroom/office more effectively. I'm thinking I could put a window air conditioner in my bedroom upstairs, and then turn the downstairs thermostat up to 78 or so. My question is though: Would this actually save me any money? I'd still be using the central air to cool the rest of the house, just not as much. Would the difference be enough to justify the cost of the window unit? In particular, I was looking at purchasing the Frigidaire FRA086AT7, which costs $200. To justify that expense in the short-term, I'd hope to save at least $40/month on my electric bill by using this strategy.