Hi Janice, There are lots of different types of greenhouse heaters and the best source is www.charleysgreenhouse.com which offer propane, electric and direct-vent gas heaters for home greenhouse owners plus all the misters, structures, containers and anything else anyone would want for a greenhouse. Charley has had this business for 33 years and runs a very reliable company. I recommend the soil heating cables to place under seedling trays. Warm soil makes for quickly sprouting seeds. Keep Growing, Marianne Binetti