Many big breeders heat the room and offer warm side heat too generally 80/90 or so. Some run no gradients at all but the control needed is fairly precise to insure every snake gets even and equal heat. The idea is to provide the exact correct core temps air for the snakes. My understanding is it is a fairly narrow window. Racks often need something to stabilize the cool end and ambient temps. This is why most have a heated room. (a rack in a room 68ºF with only hot side heating is likely to be 90/71 maybe up to 73 max but this is often felt to be too cool.) If you have normal room temps 66-69ºF it is likely some additional heating will be needed. Unless your room is very poorly insulated a oil filled heater or other convection heater will likely be the most efficient. If the room is poorly insulated rack systems can be made to work but it is not easy and the start up cost can be quite high.

My personal situation is this 350$ rack + Flexwatt 4 inch 45$ + 17 low watt flexwatt 60$ + herpstat pro 400$ insulation and additional materials 150$ machining additional parts 200$ mine is a bit of the edge as the room is often 60º winter and drops to 55º sometimes I hold 90º/80º in the rack and 77º-83º ambient under all these conditions. It is a very painstaking operation. I spend 110$ a month on power (rack plus 8 enclosures) The oil heaters were 5 times this in power bills (I needed two to heat the room to 80º very poorly insulated. In my case one winter paid the total cost of all the additional materials.