I put my bps in a rack in my house. The hot spot temp is set to be 92, and the room temp is always 74

Now I am buying more bps, so I need to move the rack to my garage. There is not heat there. I live in CA, so the room temp there will be around 60s. What can I do?

Is there any heat thing I can buy and heat up the room temp in my garage which won't cost too much power.

Thanks