I have been brewing for a year and a half and have not needed to heat at all. It does sometimes get a bit cool in the winter, but the temp in my garage has stayed up pretty well. Freezer/Fermentation temps have held well.
If I ever find I need to heat, I plan to put a covered light bulb in the freezer to keep the ambient temp in there a bit higher. But I have not had to do that to date.
Tap 1 - DanDan the Elder DIPA (Sorta Pliny Clone)
Tap 2 - Rye Rhapsody Bohemian Pilsner
Tap 3 - Irish Red (Fermenting)
Tap 4 - Raisin Brown Ale
On Deck - Some other DIPA
In Bottles: Maple Barleywine, Peanut Butter Porter, Strawberry Ginger Cream Ale, Sweet Ruination IPA