I'm in the same climate zone as you (San Diego) and it's downright chilly...I think it got up to 58 today...but last week it was near 70, yeah we're spoiled.
Ok, back on topic.
So my fermentation chamber is a 6' tall wine cooler in which I can fit two 6.5 gallon carboys. I brewed a Black IPA a few weeks ago and after the usual aeration/yeast starter/shake I noticed after two days that fermentation wasn't as vigorous as it has been/usually is with a style like that. So I take a temp reading and the interior of the cooler is 59 with the fermetometer on the carboy reading 61. That was a little too low for me. So I purchased the Fermwrap Carboy Warmer and attached that to a $8 lamp timer (something like this
). Since the Wrap is supposed to warm the cooler anywhere from 5 to 20 degrees above ambient, I set the timer to come on for four hour periods with three hour rests. I also try to keep the temp in the wine cooler stable by filling it with thermal mass (1 gallon RO water bottle bottles that I use for brewday work well).
So far, the wrap has worked great. It popped the fermenting temp from 60 to 68 and kept it there for the length of the primary (about 10 days before racking to secondary). I feel that it's been a good investment for myself, cheaper than some other options out there, and better than a temperature belt I've seen at some of the other shops.
Best of luck,