Standard wisdom says that comfortable "room temperature" is 72 degrees, but the U.S. Department of Energy estimates that you can save as much as 10 percent on overall heating/cooling costs by deviating 7 to 10 degrees from this setting for just eight hours per day. If your home is equipped with a gas HVAC system and spends the U.S. average of $875 per year on energy to run it, this means you can save almost $90 by this one simple measure. And for some people, knowing that they are helping to reduce greenhouse gas emissions is equally important.
The savings can be even greater if you learn to tolerate constant room temperatures that vary in a meaningful way from the 72-degree norm. It's not hard, for example, to become accustomed to 68 degrees as a perfectly comfortable winter temperature, and 78 degrees as a summer temperature.
This reduction is accomplished by setting your thermostat in a way that minimizes the time the furnace or air conditioning unit spends heating or cooling the indoor air. This means different things at different times of the year, and the best way to maximize energy savings will also depend somewhat on the type of system you have. Temperature setback is less effective with a hot water or steam boiler system, for example, than with a forced-air heating/cooling system.
Thermostat Settings in Winter
In the winter, saving energy with your thermostat generally means shifting it to a lower setting for any period when you won't be home or at night when you are sleeping. This will reduce the time the furnace runs to heat the house. There is a limit, however, to how low you should allow the room temperature to fall. If you allow the temperature to fall into the low 50s when you are at work, for example, the furnace will need to work long and hard to bring the temperature back up to your designated at-home temperature for your return in the evening. A more modest setback is generally better for overall energy savings.
The current energy-saving strategy says that a "normal" room temperature of 68 degrees is ideal for winter, with a nighttime temperature of about 64 degrees for sleeping and an adjustment down to no lower than 55 degrees when you are at work or on vacation.
Some experts advise that during bitterly cold weather—the type of below-zero cold that forces a furnace to run almost constantly—the best efficiency is achieved if you avoid all setbacks at night or when you are at work. In this way, the furnace will run for a short time for many intervals, rather than struggling to return the temperature to your chosen at-home room setting.
Thermostat Settings in Summer
Summer energy savings are accomplished by setting your thermostat higher than the supposed 72-degree ideal—so that the air conditioning doesn't run as often. For the time you are at work, for example, you can allow indoor temperatures to rise above 80 degrees, then adjust it back to a more comfortable temperature when you return in the evening.
It can be tempting when returning home to set the temperature very low, imagining that this will quicken the speed at which the temperature will drop. This is not true, however. Your best energy savings will be achieved with a temperature setting of about 78 degrees, and you won't reach it any faster if you set the thermostat to 65 degrees. And 76 or 78 degrees will feel comfortably cool—even cold—if outdoor temperatures are in the 90s.
Programmable or "Smart" Thermostats
All these energy savings can be acheived if you manually set your thermostat to change the temperature for the nighttime hours or while you are at work, but it becomes much easier if you install a programmable thermostat that does the work automatically. These digital thermostats can be programmed with as many as 28 different settings, allowing you to set four different temperature settings for each of the seven days of the week.
On a typical workday, for example, you can set the thermostat to raise the temperature for the early morning when you are breakfasting and preparing for work, drop it for the time when you normally leave for work, raise it again to be ready for when you get home, then drop a final time for the nighttime sleeping period. For the weekends, you can adjust the timing to accommodate a longer sleep-in period and more time spent at home. By automating the system, you can save significantly on your energy bills; a programmable thermostat is a useful investment year-round and can pay for itself in just a few months.
Another form of programmable thermostat is the so-called "learning" thermostat. With these, you spend a couple of weeks setting the thermostat manually, during which your patterns are stored by the thermostat's memory. Then when you shift to auto mode, the thermostat begins to automatically duplicate the patterns it's learned.
There are also "smart" thermostats that allow you to monitor and set your home's temperature via your smartphone or tablet. Such a thermostat will allow you, for example, to continue a temperature adjustment when you decide to extend your vacation by an extra day or if you are working late at the office on a particular day.
Acclimating to Thermostat Setbacks
Getting used to a warmer or cooler indoor temperature can take some time, but it can be very beneficial to your budget. One way to get used to a different thermostat setting is to raise or lower the temperature very gradually. For instance, if you're used to keeping it set at 70 degrees and want to work up to 78, increase the temperature by one degree each day. You'll be amazed at how quickly your body adjusts to the difference. Your system will adapt so that even the higher temperatures will feel comfortable to you.
The same is true as you are acclimating to colder room temperatures for the winter heating season. Over several days, adjust the temperature by a degree or so. You'll quickly come to feel that 68 degrees is a perfectly comfortable setting.
Other Energy-Saving Tips
The real energy-saving is accomplished if you combine thermostat setbacks with other tips for conservation and comfort:
- Manage the sun. The sun's rays can dramatically heat up your home quickly, particularly in the afternoon. In the summer, use blinds and blackout curtains to keep out the light and keep the inside cool. The strategy in the winter is the opposite: Open blinds and curtains when the sun strikes windows to capture as much solar energy as you can.
- Use outdoor air. During the summer, take advantage if nighttime temperatures fall. In many areas, temperatures can drop by as much as 20 degrees at night. In the evenings, turn off the air conditioning unit, and open the windows to let in the cooler air. When you wake up, close the windows, and pull the shades and blinds to trap the cool air inside.
- Use fans. Ceiling fans can generate a faint breeze that makes a room feel up to 4 degrees cooler, so you can set the thermostat higher and reduce your bill. Portable room fans can also give you spot cooling where you need it. While most people think of fans as being a summer cooling technique, a ceiling fan set to spin in reverse can also force room heat away from the ceiling and back toward the floor level in the winter, making the room feel warmer.
- Dress for the season. While a 68-degree indoor temperature might sound like it's quite chilly, wearing a simple light sweater through the winter months will make it feel quite comfortable. And 78 degrees won't feel at all hot in the summer if you make a point of wearing lightweight clothing. A slight adjustment to your wardrobe can keep you quite comfortable as you save money through thermostat setbacks.
- Improve insulation. Adding insulation is a more involved operation, but for long-term energy savings, make sure your walls and ceilings carry the R-value (heat transfer resistance) recommended for your region. Adding attic insulation, in particular, is usually a good idea in any region.
- Block air leaks. Along with insulation, adding the proper weatherstripping around windows and doors and blocking the gaps where air can flow around pipe openings, foundation sill plates, and other openings through walls and roofs will significantly stop warm indoor air from escaping in winter and hot outdoor air from penetrating in summer.