How to run your AC efficiently and other ways to stay cool at home

We're not yet into the dog days of summer and already we've had our fair share of heat waves and record temperatures.

We need to cool — and stay safe — during a heat wave because of the health hazards that extreme heat can present.

But running an air conditioner has environmental consequences. According to the Department of Energy (DOE), air conditioners consume about 6% of all the electricity produced in the United States. And the more electricity we use, the more we heat our surroundings and release greenhouse gases.

It is possible to stay cool and be green? We posted that question to indoor quality and energy-efficiency expert Pat Huelman of the University of Minnesota.

For Huelman, it comes down to managing three key components in your home so that your air conditioner doesn't run overtime.

"It takes a lot more energy to cool down humid air than it does dry air. Insulation plays a role, as does airtightness," he said. "Managing and reducing solar gain is a big factor. Another factor is reducing internal heat sources in your home."

Huelman's tips:

The Department of Energy suggests setting your home's thermostat to 78 degrees when it's hot out. However, Huelman said it's fine to set your air conditioner to run cooler, such as in the low 70s, depending on personal comfort, in which metabolism, a person's size and their age can all play a role.

The main culprit behind why air conditioners work so hard is humidity, so do whatever you can to keep it at bay. That means making sure your home is sealed, insulated and free of drafts.

"If you have a leaky house that brings in humid air, you're going to be chasing and chasing it," he said. "And you're going to be turning the thermostat down because it's clammy and hot."

It's also best to leave windows closed and let the air conditioner run when you're away during the day and at night. Outside temperatures may drop in the evenings, but the air tends to be more humid at night.

"Even if it feels cool, you're loading your house with humidity and it takes a lot of energy to get rid of it," Huelman said. "The good news is, the air conditioner works very efficiently when the outdoor air is cool, using less energy than when [you open the windows and then] try to bring down the humidity the next day."

So when is it efficient to open your windows? When the heat index is at least 10 degrees lower than your preferred indoor temperature, said Huelman.

However, make sure the temperature and dew point — a more telltale measurement of how muggy the air is than relative humidity is — are both meeting that 10-degree or cooler threshold. For example, if you like to set the temperature in your home to 72 degrees, make sure the temperature and the dew point are 62 degrees or lower before opening windows.

"It comes back to humidity management," Huelman said.

In addition to sealing your home from humidity, keep the sun's radiant heat from seeping in by drawing window blinds during the heat of the day. Reduce the use of lights and appliances.

"A huge part of staying cool is to not allow heat into the home in the first place," Huelman said.

Avoid turning on the oven and running the dishwasher. If you must cook, grill outdoors and run the dishwasher at night.

If your house doesn't have air conditioning, it's best to turn on fans and keep windows closed to efficiently cool your home.

"Many times keeping the house closed and having the fan on is a much better strategy than opening a window," Huelman said. "You may get a natural breeze by opening a window, but it will gradually heat the house up and bring in more humidity."

However, Huelman warned that if air is still not circulating efficiently in your home, you should open windows to avoid the dangers of heat stress.

Also, if it's too hot in your home, check for cooling centers in your community. The Salvation Army and local governments, including Hennepin and Ramsey counties, have opened cooling centers amid this wave of heat warnings.

And what to do during an air quality alert? Turn off the outside air selection on your air conditioner. This mostly applies to window units that pull some air from outside, whereas central air systems recirculate indoor air to cool a house.

"Most air conditioners will have a switch," Huelman said.