Click on a thumbnail picture below to see the full size version. 1 Entries. Saturday, March 16 View Page Planted 250' of heating cables today. If anyone can tell me about my upcoming power bill, how much and when to start them, how many degrees I can expect the soil temp to rise, if I need a green house over them, or basically any information about them that would be excellent. I put them about 4" deep and they cover around a 7' x 11' area. I'm hoping they can help with a little earlier season.