Only you can say...
Try it on max and see what happens
Then turn it down a notch each day
Until it's no longer warm enough for you
Then crank it up a notch
And make allowances for the outside temperature - if you know it's going to be very cold outside turn it up a bit.
In the Summer you may even to be able to turn it off completely
You are the World Expert on the combination of your room and your heater and how warm you like it to be.
Peccavi, December 2009