that will probably not be really necessary. even without an added heater the temperature is still likely to stay about 63 f (17.5 c) in there, with the lights being on, even though it may be 0 c outside.
plan to water about once a week, maybe twice a week if the containers are not really big enough.
the plants need to sleep 8 hours a day, so turn it off with a controller. it saves your energy bill as well. 