A/C: Leave it on or turn it off?
Is it more energy efficient when leaving the house when outside temps are between 80-85 to turn the AC off or to leave it on if I’m gone for varying lengths of time (1 hr, 2 hrs, 3-4 hrs). In other words, is it worth it to turn it off to save energy if it has to work hard to cool the house back down when I return?
Giving your A/C a rest, whether for an hour or 4, will have net energy savings. Energy use is calculated in terms of the power (watts) being used by your A/C over a certain period of time, typically measured in kilowatt hours (kWh). For example, using a 60 watt light bulb for one hour consumes 0.06 kilowatt hours of electricity.
When you turn your A/C back on, it will not use more watts to bring your home back to the proper temperature, but it may run a bit longer (kWh). So, say you turned your A/C off for four hours while you went out and grabbed dinner and a movie with your spouse, then came home and turned it back on. It may run for an extra half an hour longer to get your temperature back to where you want it – but it was still off for four hours, leaving 3.5 hours of net energy savings.