yes, the oven is on for a long time, but it's on at such a low heat,that it really isn't that bad on the environment(or,lets face it ,the electricity bill) To dry fruit i the oven, line the racks with cheesecloth and place fruit slices on top. The oven should be set at its lowest setting, reaching a temperature of no higher than 145 degree Fahrenheit,and the door should be left slightly open to allow any steam to escape (again,experts recommend positioning a fan close by to keep air circulating).