Sustainability Series: Saving on Electricity in Your Greenhouse

Charley's Team

Charley's Team | May 19, 2022

Sustainability Series: Saving on Electricity in Your Greenhouse

Buy a greenhouse they said, harness the natural power of the sun to grow things year round they said. So why does it seem like using your greenhouse is actually a pretty sizeable drain on your household electricity usage? Your local climate may hold a piece of the blame for this. Colder climates generally require more electricity in order to heat your freestanding greenhouse. There’s less sun to naturally heat your space and the colder exterior temperatures means your greenhouse will lose heat quicker. The general densities of different temperature air can also play a big role in the heat fluctuation within your growing space. Hot/warm air is less dense than cold air so it will rise and occupy the higher spaces within your space, mainly in the ceiling and rafter area. Cold air still rises, just not as quickly, so you’ll notice the loss of heat at plant level much quicker than a drop from 55-45°F. The time of year you are using your greenhouse will also factor into your energy needs. Growing things in the winter time will require heat, generally speaking. Unless you live in a climate that doesn’t get any lower than 65° on a cold day, even then, you will probably need to pump in artificial heat at some point. While it may seem like owning a greenhouse is going to increase your energy bill in an attempt supplement your grocery bill, but does it have to be that way? In this blog, I will help you explore some cheap and effective ways to use less energy while growing in your greenhouse!

Contrary to what you may believe, there are actually quite a few cost effective ways to keep your greenhouse warm during non-summer months. Some of these methods include purchasing extra materials so you might not see any savings immediately, but you will in the coming years. Other methods can be pretty labor intensive so you will save some money, but not time. So, like with most things, being more energy efficient and cost effective don’t always go hand in hand right from the start. But, before you get started, take some time to think about your next moves. Some methods may be more effective than others, but they may also require more space, time and energy investments. Depending on your greenhouse size, sun orientation and local climate, you may need to go about cutting down on energy usage differently. Gather as much information about your chosen energy saving methods as you need and tailor your plan specifically to your greenhouse. Some methods will work better than others depending on your circumstances. It’s your greenhouse, after all, why shouldn’t you customize it to what best fits your wants and needs?

First we’ll explore a couple of the cheaper, almost “quick fix” solutions to heating your greenhouse without using electricity. Most of these methods require adding something to your greenhouse. Again you might not see immediate results, at least not in your wallet, but these solutions could end up saving you time, energy and most importantly, money throughout the rest of your greenhouses life.

-Install and upkeep infrared film on the interior of your polycarbonate walls. This is probably the cheaper and easier ways to help keep your growing space warm. A lot of heat is lost through your glazing at night due to the drastic drop in outdoor temperatures once the sun goes down. A protective film, applied on the inside of your greenhouse walls, can provide an added buffer between exterior temperatures and your plants. In addition to infrared film aimed at keeping the suns heat in, you can install an anticondensate film aimed to limit the buildup of water droplets inside your greenhouse. In doing this, you can both increase the heat stored inside your greenhouse while limiting the buildup of excess moisture due to humidity. Both of these results will be beneficial to you, but this is far from a permanent solution. Poly film, while effective, is not always incredibly durable. Generally speaking, you will need to replace these films about every three years, give or take, to maintain the integrity of the film. Over time, they can become brittle and crack which essentially renders them useless, or at least much less useful than when you purchased it.

-Install and maintain both horizontal and vertical fan systems within your greenhouse. Now you may be thinking to yourself, “I already have fans and vents in my greenhouse, why do I need more?” This is a pretty valid question, but you might need to ask yourself a few questions. First being, how old are your fan systems? Older fans are, generally speaking, less energy efficient when compared to newer models. So you might be using more energy than you want simply by running older equipment. Secondly, you want to ask yourself, how effective are the fans I’m using? Fans should be placed strategically around your greenhouse to optimize air flow. As previously mentioned, warm air tends to rise and hang out around the ceiling of your greenhouse. This air can become trapped at the ceiling if your fans are not circulating the air correctly. If all of your fans are sitting at the same height, it’s less likely that the air is being distributed around evenly and that warm air pocket will stay up near your ceiling. We here at Charley’s have come up with an elegant solution to this problem with our Heat Saver Fan. This is a fan that attaches to the rafters of your greenhouse and pushes warm air back down to plant level. These fans have been shown to reduce heating costs up to 20%. Again, there is an upfront cost involved in this method so you may not see savings immediately, but fans last quite a few years before they experience mechanical problems so you will observe savings for years to come.

-Boilers and Hot Water Heaters. Now, these options are electricity efficient, but they may not be entirely energy friendly. Many boilers use gasoline to operate so you may save on one monthly bill, but probably see an increase in another. These systems essentially heat water in your greenhouse which can both increase temperature as well as provide some necessary moisture for your plants. In addition, water is a great temperature sink. Water has a much higher specific heat energy than air which essentially means water requires a lot more energy to increase in temperature than air. This to say, large bodies of water will stay warmer than the surrounding air when cold temperatures set in. Large enough bodies of water will even emit some heat that it loses as it cools down, so even if you keep large buckets of water in your greenhouse you can help keep the temperatures stable.

-Environmental Control Systems. These are essentially systems that will do the work for you in cutting down on energy usage. They essentially only turn on your heating systems and lights only when entirely necessary. Generally speaking, they will kick on your most energy efficient heaters and lights before using the more energy intensive units, again only when totally necessary. These systems can reduce your monthly bill by staying on top of your energy usage for you. Now, you can do this for yourself, if you have the time and energy to go back and forth from your greenhouse to switch heaters, fans and lights by yourself. Essentially these systems, while requiring a sizeable monetary investment upfront, can save you time and money in the long run.

-Composting! Probably one of the most cost effective way to keep your greenhouse warm is composting. The natural process of breaking down organic matter releases heat as a byproduct. If you compost inside of your greenhouse, the heat released from that system will be added to your growing space. This method may take up some extra space within your greenhouse growing space, but there is no electricity or other energy source required to generate the heat. A compost bin may take up some extra space inside your greenhouse, but it is a triple threat by providing you some thermal mass, a helpful soil additive as well as providing you an outlet for sustainable waste management.

strong>-Update your heaters. Updating your heating systems is probably the easiest way to make a large impact on your energy usage. Older model heaters are, generally speaking, less energy efficient than their current counterparts. However, this is likely to be the most expensive option, at least in the short run. New heater systems will come with a big price tag, especially if you’re buying a higher end model. However, as mentioned earlier, this is probably the quickest and easiest way to heat your greenhouse while lowering your electricity bill. New systems even have features that can do things like shut off the heater when they reach a set temperature. This will allow you to simply set up your new heater and let it get to work without having to constantly go in and check the ambient temperature in your greenhouse.

-Under bench or root system heating. Installing systems that emit heat from below your plants will help make sure you are only heating what you need to. Many fan based heaters can be rather inefficient as they spew heat indiscriminately into your greenhouse. This can be less than optimal as your plants are really the only thing in your greenhouse that needs heat. It’s nice to keep the ambient temperature in your greenhouse high, but it can be an energy drain. So long as you are keeping the soil and roots of your plants at the proper temperature, you are doing enough. Depending on the plants you are growing, you may need to do a little more than just low level (literally and figuratively) heating, tropical plants for example require more warmth and humidity.

There are quite a few more ways you could keep your greenhouse warm outside of electric generated heat. Proper insulation during cold weather, sealing any cracks or making sure your greenhouse is in a sunny spot can be very helpful. As mentioned earlier, make sure the options you are exploring work for your specific setup. Until next week, thanks for reading!