Avoid incandescent bulbs.

Philips Medium LED 100-Watt Equivalent Daylight Bulb $15 at acehardware.com

“Without knowing it, your lightbulbs might be causing more heat in your apartment than you think,” designer Alison Petty advises. Adds smart-home consultant Eugene Fiks, “If someone is using your average incandescent bulbs, they’re disseminating heat.” Instead, he says, use climatefriendly LED bulbs to keep your space far cooler

without having to turn off any lights. “You’ll also notice energy savings on your bill,” says Fiks.