Turning off some household items before you leave on vacation can be a smart way to save money. That’s the advice of a United Kingdom company specializing in solar Energy installations and a North Carolina-based supplier of electricity and natural gas.

Water heaters that are left on while traveling can be the biggest money drain, according to London-based MakeMyHouseGreen. Refrigerators, freezers and other devices also add to absent homeowners’ electric bills.

“Many families like to leave their heating on for a few hours a day while they are away to keep the house warm and water ready to be used,” MakeMyHouseGreen advises. “However, they might not realize the cost they’re adding to their holiday. If nobody is going to be using hot water for a few days or weeks, turn the heater off, or set it to vacation mode to save energy.”

Duke Energy, based in Charlotte, North Carolina, also advises turning off an electric water heater at the breaker panel if a homeowner is away for a few days. Most water heaters will reheat the water to a set temperature in about 60 minutes, the company says.

Duke Energy also encourages homeowners to use the “vacation” mode if they have a programmable thermostat—or make a manual thermostat a few degrees cooler before heading out on vacation.

“A change of just three degrees for 24 hours a day can save 30% on your heating costs,” Duke Energy says. “Also, set the fan to ‘auto,’ not ‘on.’ Leaving the fan on all the time costs up to $25 a month. If the forecast is for mild weather, consider turning the system off completely.”

Fridges and freezers might not seem like obvious candidates to save energy, but MakeMyHouseGreen suggests that they might.

“If you’re going on an extended holiday, consider emptying your fridge and freezer and turning them off,” the UK company says. “For shorter trips, set them to a higher but still safe temperature.”

If you don’t turn off your refrigerator, keep the fridge and freezer full and tightly packed, Duke Energy says, because a fully stocked refrigerator keeps cold better than an empty one. You can fill the fridge with water containers and ice trays instead of food. Conserve even more energy, the company says, by adjusting the thermostats on your refrigerator and freezer to higher settings—38 degrees for the refrigerator and 5 degrees for the freezer.

When travelers are away from home, many electronics and appliances continue to draw “phantom” power.

“On their own, they don’t account for much, but many devices can add up over a period of time,” MakeMyHouseGreen says. “Unplug devices like TVs, computers, microwaves and chargers.

Coffee makers, cable boxes, game consoles and rechargeable toothbrushes also are phantom power users, Duke Energy says.

Many people who travel leave a light or two on at home for security reasons.

“While it’s a common practice to leave a light on for security reasons, it’s often unnecessary and wasteful,” MakeMyHouse Green says. “Instead, consider investing in a timer that can turn your lights on and off at set times, giving the appearance that someone is home without wasting electricity.”

To maximize savings while away from home, homeowners could turn everything off at the fuse panel.

“However, just make sure you don’t accidentally turn off a freezer that is still full or an alarm system you’re relying on,” the UK company warns.