Running a greenhouse during the colder winter months can be challenging, but the reward of having fresh produce or flowers year-round is well worth the extra work. Heating is a main component of having a successful greenhouse from fall to winter, and you will most likely have to install a heating system to regulate the temperature. For smaller or beginner greenhouses, the best options are electric heaters and soil warming trays. Soil warming trays in particular cut down on heating costs because they keep the plant temperature constant but allow the rest of the greenhouse to stay cooler.
Choose an electric heater fan that has an easy-to-control thermostat, specific for greenhouse use (other heaters will be a fire hazard). Although this is one of the most popular options, it is also one of the most expensive. Also check with the manufacturer to choose one that is appropriate for the size of your greenhouse so you know it will heat properly.
Plug in the electric heater right before the first frost to provide well-circulated heat. Follow the manufacturer's directions on how to run the heater since this will depend on the type, size and brand that you choose. This also depends on the materials use in your greenhouse. For example, a greenhouse made with poly sheeting will probably require a lower heat setting than polycarbonate or glass.
Monitor your electric heater based upon what your specific plant needs are, keeping a constant temperature.
Soil Warming Cables and Trays
Purchase plastic propagating trays that have soil warming cables in the base that are connected to a standard electricity supply (available online or at gardening supply stores). Try to find ones with a built-in thermostat so you can control the temperature.
Set your planter trays of vegetation into the soil warming trays. If this is not possible because of size, transplant your plants to the soil warming trays in their properly prepared soil.
Plug the warming trays into an electric outlet in the greenhouse.
Set the thermostat to the desired temperature. Monitor to ensure it is working correctly.