Most residential mowers are powered; there's an engine and usually some sort of traction device to make the machine easy to push around for an extended period of time. According to caloriesperhour.com, a site that calculates calorie burning for thousands of activities, a 150-pound person will burn 306 calories an hour by pushing a power mower.
Some homeowners have small lawns or use non-powered motors for ecological reasons. While old hand mowers were difficult to use, modern designs move (and cut) much more smoothly. According to caloriesperhour.com, a 150-pound person will burn about 408 calories an hour by pushing a hand mower.
Even sitting on a riding mower can burn a few calories; your body needs energy to perform its basic functions, and there is a bit of turning, steering and balance involved. According to caloriesperhour.com, a 150-pound person will burn about 170 calories riding a power mower for an hour.
How Your Body Burns Calories
Your body needs calories to do everything it does; breathing, organ function, everything. It needs more calories the more active you are. This is why exercise is key to weight loss; while consuming fewer calories will help you balance your energy intake with your energy consumed, exercise will help your body burn more calories than it takes in---this is what causes you to burn fat and lose weight.
The larger you are, the more energy you require to move. Calorie burning also depends on your body's metabolism, or the rate at which it consumes calories. People with higher metabolisms burn more calories and require more energy to get through the day.