Guide to Solar Greenhouse Heaters

Last Updated on June 15, 2023 by Kimberly Crawford

Humanity is increasingly thinking about the future, so they begin to show increased interest in environmentally friendly sources of raw materials. Solar energy has become one of such objects of general demand. It is in use to generate electricity in homes and businesses, to charge electric cars, for water and heating, as well as a pool heater and for growing plants in greenhouses.

Greenhouse solar heaters are an eco-friendly and economical way to heat your greenhouse during the colder months. Solar energy is in use to heat the air inside greenhouses, providing plants with a warmer and more comfortable environment. However, do not hurry up to purchase without learning about them as much as possible.  We offer a guide to solar heaters for greenhouses.

What Is a Solar Greenhouse Heater?

A solar heating system for greenhouses is a solar panel that converts solar energy into heat and distributes it. Solar panels can only generate electricity when sunlight hits their surface. In other words, if it is night outside or the system is installed incorrectly, and direct sunlight does not fall on its surface, there will be no heat in the greenhouse.

Solar heating systems are indispensable things for a greenhouse. They allow you to create optimal conditions for growing various crops and plants throughout the year. At the same time, their help increases the growing season of plants.

what is solar greenhouse heater

Source: ResearchGate

How to Heat a Greenhouse at Night?

The problem with cloudy days and nighttime is fixable, but if the installation was done incorrectly, nothing will help. The only option is to remove the panels and reinstall them properly, but that’s expensive. That is why, it is quite essential to do everything right from the start. If you are not experienced – entrust the installation of solar systems to professionals and forget about any problems.

To keep the greenhouse warm even at night, it is enough to buy a storage or battery that will accumulate excess energy during the day. Now at night and on a cloudy day, your solar heating will work like during the day.

Advantages of Solar Panels for Greenhouses

A solar heater for a greenhouse is not only warm for your plants in winter but also has many other advantages.

Saving energy and budgetThere is no need to waste electricity from fuel power plants, which will significantly save your budget.
Environmentally friendly power sourceSolar energy is a renewable energy source, which makes it green.
Reliability and durabilityWith proper installation, use, and care, solar heaters will last more than 20 years and will not leave your greenhouse without heat at the most inopportune moment.
Ease of careYou do not need to constantly monitor the cleanliness of the panels, the main thing is to clean them after heavy rainfall.
Ease of installationYou do not need to have a specialized education to fix the system, but it is still better to consult with professionals.

Solar panels are a really good investment for any purpose where they can be useful.

How To Choose and Maintain a Solar-powered Heater?

Making the right choice of a solar heater for a greenhouse without the slightest experience is a difficult task. We are going to give you the most comprehensive information, but if you still hesitate, consult a professional. Several nuances are worth paying attention to.

Heater Type

Distinguish active and passive solar heater types.

Active solar heating systems use pumps or fans to move a coolant (usually water) through a solar collector and a heat exchanger that transfers heat to the greenhouse heating system. They often require high power to operate the plant. But at the same time, they provide the optimal amount of warm air that circulates throughout the greenhouse.

Passive solar heating systems, in contrast, do not require an external energy source. They use the design features of the greenhouse and panel to naturally transfer the outside heat of the room. So, they collect sunlight through transparent materials, such as glass or polycarbonate sheets, and then convert them into thermal energy.

Each type of system has its advantages and possibilities, and the choice depends on many factors such as climatic conditions and structural features of the building.

Greenhouse Area

The size of the solar-powered heater will directly depend on the size of your greenhouse and the amount of required heat. A general rule of thumb is to aim for a heater that can provide at least 10% heat energy of your greenhouse’s volume. You will need a heater that can provide at least 80 square feet of heat for a greenhouse 100 square feet and 8 feet high. The most commonly used panel options are 20-40 watts per square foot.

But if you have an open greenhouse, everything will also depend on the amount of natural sunlight that hits the plants in your greenhouse.

Types of Solar Cells

According to the type of solar cells, solar heaters for greenhouses can be divided into monocrystalline and polycrystalline.

Monocrystalline solar cells are made from a single silicon crystal, which gives a uniform dark blue color. A monocrystalline solar cell converts energy more efficiently than a polycrystalline one. They are compact, cylindrical, and have a higher conversion efficiency. However, the manufacture of single-crystal chemical elements is more dispersed and laborious, which leads to an increase in the cost of the final product. The efficiency is about 15-20%.

Polycrystalline solar cells are already made from small silicon crystals that are blue with light spots. They are significantly cheaper than single crystals but have slightly lower efficiency and take up more space.

main solar panel types

 Source: Treehugger

Plant Type

The plants you plan to exhibit will also determine which solar heater to buy. Each plant has its optimum temperature. For example, tomatoes need a lot of heat in the winter.

But there is the other side of the coin. Some cultures themselves produce a large amount of heat. Learn more about this question.

Insulation Feature

The greenhouse itself must be strong enough and insulated. After all, if you install a panel, but at the same time, the heat will constantly leave through the cracks, there will be no heat for the crops. In addition, a well-insulated greenhouse will save on the purchase of panels.

Installation Features

Installing a greenhouse solar heater will depend on the type you choose. Passive heaters are best installed on the south side of the greenhouse. This is where they get the most sunlight. Active heaters must be installed close to the power source. For example, with a solar panel or a battery. They also need to be connected to a fan or pump to circulate warm air.

But most importantly, the solar panel heater should be easy to install. It is better if it can be installed by direct mounting on any surface. It is important to remember the rules regarding the terrain. The panels should be away from shade and installed in places where there are at least a few hours of sun per day. And professionals who should be involved in the installation of systems know about the technical rules and safety features.


Take care of the various controls. They will greatly simplify the operation of the heating system and provide additional security. For example, buy a mounting bracket, a reset controller, or a temperature sensor.


Solar companies offer many options for greenhouse heating systems. They can have a fairly large range in cost. Try to make the right calculations and understand what your budget is. And then start choosing the best option.

System Care

To keep your solar greenhouse heater running efficiently, it is important to keep it clean and maintain it on time. Passive heaters in particular will need to be cleaned regularly to maintain their transparency and ability to collect sunlight. Active heaters also need to be serviced, replacing any components such as fans or pumps if they become damaged or stop working. It is better to call the technical service once every six months. Then your panels will last a long time.

Helpful tips

While greenhouse solar heaters are an effective way to keep a greenhouse warm, there are other ways to keep plants comfortable during the colder months. For instance, insulating the greenhouse walls, using a thermal blanket at night, and venting the greenhouse well during the day can prevent overheating.


We have reviewed a guide that will help you when choosing a solar system for heating greenhouses. Use it on your way. Take into account as many details as possible from the choice of panel type to the calculation of the greenhouse area and the optimal cost. And then your purchase will solve all your problems with the lack of heat in the greenhouse in the winter.