I run some tanks in my garage as well. I find using acrylic tanks, foam insulation boards everywhere that's practical, and tight fitting lids minimize the heaters work. Right now I only have my 40 gal reef tank and a 40 gal fry growout in my garage. At times there have been a 125 gal setup as well. I find that using the aforementioned methods help dramatically in keep the pge as low as possible