No matter how mild your winter may have been so far, at some point, it will get cold. And when it does, instead of reaching for the thermostat to flick it up a degree or two, consider cleaning your house instead. Getting active by picking up, mopping up, or sweeping up may increase your heart rate a tad and make you feel just as warm as spending more money on your energy bill. Best of all, your house will be spic-n-span. This also works by doing some light calisthenics. Your utility bill and waistline thank you.