There’s nothing nicer than enjoying fresh, homegrown vegetables in winter. Whether you are a greenhouse pro or a hobby enthusiast, a good greenhouse heater allows you to grow plants all year long. The amount of greenhouse heating you need largely depends on your climate.
To decide which heating system to use, one of the most important factors is the possibilities your greenhouse and house offer you. If you have a greenhouse that is built against your house, you are probably able to extend your central heating system there. If your greenhouse is far away and your gas pipes aren’t accessible you will probably have to go for an electrical heater. And what about solar greenhouse heaters? This new type of environmentally friendly heating is currently becoming more and more popular!
You can choose a simpler model that you turn on and off depending on the outside temperature or you can choose to install a thermostat in your greenhouse to heat automatically.
Before heating your greenhouse, make sure it’s insulated well. Bubble wrap can be helpful during winter to fight off the cold. Find out more about this in our article about insulating your greenhouse.
I will walk you through the different types of greenhouse heaters and the pro’s and con’s per system. These are based mostly on heating hobby greenhouses, as heating, an industrial or commercial greenhouse needs a whole other approach.
What are BTU’s?
Before you can choose which kind of heater you want, you need to decide on how big or strong this heater should be. To know what you have to look for when purchasing one, you need to know the number of BTU’s you will need. BTU’s (or British Thermal Units) are used to determine how strong your appliance needs to be to heat up a space. The BTU is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. You can calculate the number of BTUs needed to heat your space yourself with this simple formula:
Cubic feet to be heated * 0.133 * Desired temperature rise = BTUs needed per hour
You calculate the desired temperature rise simply by subtracting the lowest outside temperature from the desired inside temperature.
When you buy a heater, the number of BTUs will tell you which one you’ll need!
Electrical greenhouse heaters
Electrical heaters are quickly and easily installed in your greenhouse. You can decide whether you want to add a thermostat or regulate the temperature yourself. They represent a very safe option for your plants and vegetables.
Electrical greenhouse heaters are mainly divided into infrared heaters and convective heaters. Convective or forced air heaters are probably the most common hobby greenhouse heaters in North-America. They work great with programmable thermostats, given the system’s short time to recover. They provide a strong and stable heat source that results in rapid plant growth. With forced-air heating, it’s very important to keep doors and windows closed as much as possible, as the hot air will escape when they are opened.
Infrared heaters are becoming more and more popular. They are usually more budget-friendly than the forced air heaters as they save more energy. The benefit of infrared heaters is that they directly heat up certain parts or objects of the room. When these objects are heated, the surrounding air will become warmer.
Electrical greenhouse heaters are definitely the most used source of heating because they have very little downsides. One of the risks of using electrical heaters is that they can on very rare occasions cause a fire. It’s something that you should be aware of, although chances are very slim this will happen.
When you’re using an electric greenhouse heater (especially one with a thermostat) you don’t need to worry about frost protection and your greenhouse should easily survive cold winters!
Gas greenhouse heaters
In general, you can make the same distinction in gas greenhouse heaters as you can in electrical heaters. You also have the option to heat with forced air or infrared, but when you consider heating your greenhouse on gas, there’s a couple of extra things you have to take into account. The biggest benefit of heating on gas is that you don’t need electricity in your greenhouse. When you heat your greenhouse with gas you can choose between natural gas or propane gas.
Propane gas versus natural gas
- Propane gas is a part of natural gas in its raw state, at gas processing facilities hydrocarbon will be separated from the other gases. Natural gas consists mainly out of methane but includes a number of other gases, such as propane, butane, ethane.
- When you consider pricing, natural gas will be less expensive than propane gas
- A big difference for me is that propane gas is not harmful to the environment whereas natural gas is considered a greenhouse gas
- Natural gas is distributed through a pipeline network, whereas propane will come in tanks
Without getting too technical, I would make the choice between natural gas and propane mostly a practical one. Do you have natural gas pipelines that can reach the greenhouse or are you already heating your house on gas right now? Then natural gas will probably be the more effective option for you. If you don’t have pipelines that can reach your greenhouse, propane gas is your way to go!
Solar greenhouse heaters
The most recent kind of greenhouse heaters is the solar greenhouse heaters. These have immediately jumped to the top of our greenhouse heating list, as they are kind to the environment and don’t need gas cans or electrical wiring.
Solar panels capture the solar energy and convert this energy into electric current. Invest in a solar greenhouse heater kit, which will consist of all the panels and wires you’ll need.
Make sure to hook up a battery to your solar panel system. You need this battery to store the energy your solar panels generate during the day, as you don’t need extra heating while the sun is shining. The heating should be working during the night or on very cold and dark days, so a battery is crucial to release the electricity when your plants and seeds most need it! Hook up a heating device (that matches the voltage your battery) and you’re good to go!
The amount of solar panels you can install, depends on the size and surface of your greenhouse. The more solar panels, the more electricity you’ll be able to generate. Make sure to research how many panels you can install and how much electricity you’ll need to heat your greenhouse. Don’t worry if you don’t live in sunny California, the solar panels don’t need direct sunlight to generate electricity. Even on a cloudy day, the panels can capture solar energy!
The best choice for you?
To wrap up this buyers guide, I would base my decision on how to heat your greenhouse on the following factors:
- What’s the climate like where you live (especially during winters)?
- How big is your greenhouse?
- How much are you willing to spend?
- Are you already heating on gas?
- Do you need a thermostat?
- What’s the number of BTUs you’ll need?
As we are big fans of being environmentally friendly and looking after our beautiful planet, it’s clear that solar heating is our favorite, but we completely understand it’s not the right option for everyone. The most important thing is that the heating device you choose will allow you to grow vegetables year-round!