You might have success if you had a dimmer switch to attach to your light... but ONLY if your household temperature NEVER varies by more than 2 degrees. Otherwise, your best bet is to spend the $17 to buy a bimetal thermostat. Or you can do it cheaper with a modified water heater thermostat, but you won't have the same amount of control. If you spend the money up front now for the thermostat, you'll have a serviceable incubator that you can use every year. The broody hen turns her eggs many times every day while she is incubating.