In southern Arizona, summer is air conditioning season. June, July, and August bring our highest electric bills that burden budget-minded families, including myself. Last August was my highest bill of the year, totaling about $240. After a few household modifications, this year’s bill was only $140, with zero decrease in comfort. Here’s what I did:
1) Installed more attic insulation. Insulation not only keeps warm air in the house in the winter, but also keeps the hot outside temperatures from migrating inside during the summer, just like the insulated cooler you take on a picnic. My attic gets hot. Really hot. And the air conditioning ductwork runs through the attic. The insulation prevents the hot attic air from heating up the ductwork, and from conducting through the ceiling of the house. My house used to have only about 3 inches of loose cellulose insulation. Now it has 14 inches of fiberglass roll insulation, installed over the ceiling, and over the ductwork.
2) Speaking of a hot attic, reducing the air temperature in the attic also reduces how much heat transfers through the ceiling. Think of that picnic cooler. The ice inside lasts longer on a cool day than a hot day. My attic formerly had only two vents, with an area of about two square feet each, under the eaves on each end of the house. Last winter, I added a turbine vent at the peak of the roof. Turbine vents spin in the wind, and draw air out of the attic.
3) I installed a programmable thermostat, and switched to a time-of-use rate plan This item cost me about 30 bucks, and saves me at least that much every month since I installed it. The thermostat has different programs that set the thermostat at different temperatures depending on the day of the week and the time of day. Thus, I set my thermostat higher when I am out of the house at work, and lower when I am at home. Setting the thermostat to a higher temperature while I am not home means the air conditioning runs less and I save money.
A time-of-use plan means my electric provider charges different rates during the day and nighttime hours. From their standpoint, they want to reduce electric demand during peak hours so that they do not have to increase their capacity by building new power plants. They encourage this by charging more for electricity during the day, and less during the night. I’ve programmed my thermostat to keep the house cool from 9pm until 10am the next morning when the rate is lower and the air conditioning is more efficient do to the cooler nighttime air. Air conditioning works most efficiently when the difference in temperature between the inside and outside is the smallest.