Racks can save electricity if you have a stable room temp. If the room dont fluctuate a lot then a rack can save money over time. I dont know how much as i never used heat lamps or tanks for snakes. Only time i used tanks was when i was building my racks.

If you add the wattages up you can go from there on the savings and work in the room temp. Which will play a roll as in how much the heat turns on and off with the thermostat.