The Battle for Efficiency: Constant vs. Changing Temps

Constant vs. Changing Temperatures Air Conditioner


The day-to-day maintenance of a home can be costly. Whether you are in a freestanding home, a condo, or an apartment, maintenance and repair costs can bring down your budget. Most people try their best to maintain reasonable household maintenance budgets, and to cut back where they can.

When it comes to HVAC savings, we get a common question from our customers: is it more efficient to leave my air conditioner set to a constant temperature, or to change the temperature over the course of the day? Well, the answer is: it’s not that straightforward. If you leave your air conditioner set to a constant temperature, your air conditioner will have to work to keep that temperature steady even when you’re not at home. But if you change the temperature during the day or night by more than a few degrees, then you lose some energy savings, because your air conditioner will have to work harder to bring the temperature back to the lower temperature you want when you get home.

So what’s the solution? A programmable thermostat.

A programmable thermostat is one of the best ways you can save money on your cooling bills, but only if you use the thermostat properly. These types of thermostats allow you to program a cycle that works for your home and stays consistent. For example, you can program a smart thermostat to keep your home a little warmer during the daytime hours when you’re away from home, and a little cooler during the hours that you are typically at home. Allowing a cycle to stay consistent helps to keep your system a little more efficient, which can lead to a small savings in your energy bill.

In order for a programmable thermostat to end up saving you money, however, the temperature changes between day and night must be no more than one or two degrees. Each programmable thermostat has slightly different guidelines, so make sure you read and adhere to manufacturer suggestions for your particular thermostat, but in general larger temperature changes will lead to greater energy use as your HVAC system tries to keep up with the changes. This means any cost savings associated with a programmable thermostat will disappear as well.

Another thing to consider when selecting a programmable thermostat is the schedule your family usually runs on during the week. If your schedule is pretty regular, you might want to invest in a 5-2 or 5-1-1 programming. This allows you to set one schedule for five days a week (think Monday-Friday), and a different schedule for weekends. If your family doesn’t have a set schedule, you can spend slightly more and purchase a 7-day thermostat that will allow you to program a schedule for each individual day of the week. And if you really want to make the most of your HVAC system, you can invest in a smart thermostat, such as Nest. For a few hundred dollars, the smart thermostat will automatically determine the best energy saving schedule for your home, and allow household members to control the HVAC unit via a wi-fi connection.

If you cannot (or don’t want to) switch to a programmable thermostat, you can lower or raise your thermostat temperature during the day or at night and see some savings if you remember to only change the temperature by one or two degrees, and try to be as consistent as possible in the timing of your changes. But if you’re opting to make larger changes in temperature over the course of the day, you are likely better off picking a median comfortable temperature that you enjoy, and having your AC hold that temperature during the day.