Greenhouse Solar Panels (Full Guide)

What’s the most efficient way of heating a greenhouse, you might be wondering? Considering that it always represents a high cost, it’s important to evaluate thoroughly the different options available. 

If your greenhouse is well designed, you might not even need to use any external heating source. But if it’s not the case, using greenhouse solar panels can be a good alternative to gas or electricity.  

We’ll talk about the following aspects of this topic, among others:

  • Heating a greenhouse using solar panels
  • How to an efficient solar-powered greenhouse
  • What is a passive solar greenhouse
  • Details about solar power costs and solar panel kits

Keep reading so that you don’t miss out on important information about heating your greenhouse.

Solar panels inside a greenhouse

Can I Use Solar Panels for Greenhouse Heating?

Heating a greenhouse in the winter, whether you choose electricity or gas-powered heating elements, can be quite expensive. Installing solar panels to power your greenhouse heating can end up saving you a lot of money on heating. 

If you plan to use your greenhouse throughout the winter, and especially if you live somewhere with a cold winter climate, ensuring proper heating is a must. 

While it is possible to maintain a temperature of 45 degrees using passive solar power, installing additional heating elements can give you peace of mind knowing that your greenhouse will always be warm enough.

How Do You Keep a Greenhouse Warm Without Electricity?

It is entirely possible to heat a greenhouse without the use of electricity. Depending on the climate where you live, this task could prove simple or more difficult.

Many aspects of the design of your greenhouse will contribute to whether it can keep warm without electricity. Any parts of the wall that do not need to let light in should be well insulated. 

The north wall (so long as you live in the northern hemisphere) in particular does not need to be transparent and should be well insulated.

You can use elements inside your greenhouse that absorb heat. For small greenhouses, you can line the northern wall with gallon jugs filled with water and painted black. 

For a larger greenhouse, you can use a black rain barrel or 55-gallon drum. A cement or pea gravel floor is an effective way to absorb heat as well.

solar panels tilting in a greenhouse

What Is the Best Way to Heat a Greenhouse?

You have several options when choosing how to heat your greenhouse. You can design a passive solar greenhouse that does not need any additional heating besides the sun.

If this doesn’t work for your greenhouse, your options are to use heaters powered by gas, electricity, or solar. While gas is a cheaper option to heat your greenhouse, electricity is more effective.

While installation of greenhouse solar panels can be pricey, its effectiveness and the money you save in the long run could make solar the best way to heat your greenhouse.

Can a Greenhouse Be Used in the Winter?

Depending on the climate where you live, using a greenhouse during the winter could seem like a far-fetched idea. 

The transparent greenhouse panels cause the temperature inside the greenhouse to be warmer than the outside temperature, allowing the greenhouse to be used outside of the typical growing season. 

If you design or retrofit your greenhouse to retain heat, either passive solar or from other heating elements, you can use your greenhouse year-round: even in the winter.

Do Greenhouses Need to Be Heated in the Winter?

If you live in a warm climate, you might not need to worry too much about heating your greenhouse in the winter.

Install a thermometer inside your greenhouse, and as long as temperatures stay above 45 degrees (or warmer depending on the plants you are growing), you will be fine.

However, those of us who live in colder climates need to give more thought to the temperature of our greenhouses. If temperatures are below freezing in the winter, the greenhouse needs to be heated.

Greenhouse and house in the distance with solar

How Are Greenhouses Heated in Winter?

There are many ways to keep your greenhouse warm all winter. The three most common ways to heat a greenhouse are using passive solar heat, gas, or electricity.

Depending on how cold your winters are and how efficient your greenhouse is, you may be able to generate and maintain enough passive solar heat to keep your greenhouse thriving all winter long. 

However, if you live somewhere that experiences very cold winters, even the most efficient greenhouses may not generate enough warmth to keep your plants happy.

Gas is an inexpensive option for heating a greenhouse, but it has its drawbacks as well. Gas heaters turn off when oxygen levels are depleted, which can happen fairly frequently in a nearly-airtight greenhouse.

Gas is only 80% efficient for heating a greenhouse, mainly due to heat lost through the necessary exhaust ports.

With 100% efficiency, electricity is the best way to heat your greenhouse during the winter. However, electricity is the most expensive option.

Using greenhouse solar panels to generate electricity can offset this cost, possibly even eliminating the cost if you can generate enough electricity.

How Can I Heat My Greenhouse for Free in the Winter?

Heating a greenhouse, especially in the winter, can be very expensive depending on the size of your greenhouse and how low the temperatures dip in your region. However, it is possible to find ways to heat your greenhouse effectively for very little cost, or even for free eventually.

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The first way to do this is through the use of passive solar power. In many cases, however, the design features of a passive solar greenhouse may not be sufficient to maintain the minimum temperature needed. 

If you want to use your greenhouse year-round but passive solar isn’t going to cut it for your greenhouse, solar power can offer a cost-effective alternative.

Although depending on the size of your greenhouse, the initial cost of installing solar panels may be quite expensive, you will end up saving money in the long run. Greenhouse solar panels can even completely replace any other heating sources, meaning you would have no ongoing costs to heat your greenhouse.

Passive Solar Greenhouse

A passive solar greenhouse is designed to optimize the heat retained and minimize the heat lost so that your greenhouse can be heated without any additional heat source. Many aspects of your greenhouse’s design will contribute to the amount of heat it can retain.

For optimal sunlight, your greenhouse should face somewhere between the south and southeast (if you are in the northern hemisphere). Any interior walls that are not transparent should be painted white; this will reflect more light. Black jugs or barrels of water can be used as a “heat sink” to absorb heat.

Greenhouse and solar panels on a roof house

What Is Passive Solar Greenhouse?

Technically, all greenhouses are solar-powered. The purpose of a greenhouse is to harness energy from the sun to help maintain the ideal temperature for plants to grow. 

However, with all the modern advances in solar power, we often think of “solar-powered” as only referring to energy produced using some sort of solar panels.

Passive Solar Greenhouses do not rely on any additional source of heating. They optimize the heat retained by the sun and minimize heat loss so that the greenhouse can stay properly heated without any gas, electrical, or solar heating.

With proper insulation, you may be able to have a passive solar greenhouse even if you live in a very cold climate.

What Is the Best Direction to Build a Greenhouse?

When building a greenhouse, you will want to ensure that you choose a location and orientation that will give your greenhouse optimal sun exposure. Your greenhouse should receive at least six hours of sun a day. 

In the United States or anywhere in the northern hemisphere, a greenhouse should ideally be oriented facing south or southeast. This will provide the most sun exposure and, therefore, heat for your plants.

How Many Solar Panels Do You Need to Heat a Greenhouse?

So for a small greenhouse, one solar panel could be sufficient to heat the entire space. Larger greenhouses will require additional solar panels to ensure enough electricity to keep the greenhouse at an ideal temperature.

The number of solar panels needed to heat your greenhouse will vary widely depending on the size of your greenhouse and your winter climate. 

A solar panel produces between 10 and 35-kilowatt hours of electricity per square foot per year. The standard size for a solar panel is slightly larger than three by five feet, so the kilowatt-hours produced by a single solar panel will be somewhere between 150 and 525-kilowatt hours per year. 

Transparent Solar Panels for Greenhouses

One problem that the use of solar power creates is figuring out where to put your greenhouse solar panels. At 3 by 5 feet, a typical solar panel is rather large. 

While the roof is an ideal place for solar panels to receive optimal sunlight, this poses a problem for greenhouses. You don’t want to cover your greenhouse with solar panels that block the sunlight.

One solution is transparent solar panels. The technology for these innovative greenhouse solar panels is still being developed, so transparent solar panels are very expensive and are not yet as efficient as regular solar panels. 

However, as this technology advances, transparent solar panels could become the future of solar greenhouses.

Is There a Solar Heater?

Many solar greenhouse heaters are available at a range of price points. If you have a smaller greenhouse, an inexpensive solar heater (many are in the $100-$200 range) could be sufficient to heat your greenhouse garden year-round. 

However, if you have a large greenhouse, a solar greenhouse heating kit that heats your entire greenhouse can end up being very pricey.

Solar panels as a garden shade

How Do You Build a Solar Powered Greenhouse?

Before you begin building your solar-powered greenhouse, there are many things you will need to consider. First of all, a location that receives adequate sunlight is important. Next, you will need to figure out the power needs of your greenhouse. 

The size and location of your greenhouse as well as the equipment you will need will determine how many solar panels you will need to power your greenhouse.

Using the best building materials and proper insulation will ensure that you retain as much heat as possible, minimizing your power needs.

Final considerations before building include ventilation and utilizing thermal energy by using concrete, gravel, or a heat sink.

How to Build a Solar Powered Greenhouse

Greenhouses need to be in a location that receives ample sunlight. This is especially important for a solar-powered greenhouse. Choose a location facing south or southeast for optimal sunlight.

Choose building materials and insulation that will retain the most heat. Paint any non-transparent interior walls white to reflect sunlight, and use concrete or gravel floors to absorb heat. Jugs or barrels of water painted black can be used as a “heat sink” to absorb heat.

Find a location for your greenhouse solar panels where they can be south-facing without blocking too much necessary sunlight from your greenhouse.

How Do You Figure Out How Many Solar Panels I Need to Run My Hydroponic Garden?

Hydroponic gardening consumes a lot of energy due to the lighting needs. If you want to convert your hydroponic garden to solar power, you can save a lot of money on energy costs in the long run.

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To figure out how many solar panels you will need to run your hydroponic garden, you first need to calculate your energy consumption. 

Look at your daily wattage consumed to estimate your yearly energy needs. Convert the watts to kilowatts by dividing by 1000. You can then calculate how many solar panels you need based on the kilowatts produced by a standard solar panel (between 150 and 525-kilowatt hours per year).

greenhouse Solar FAQs

If you still have some questions unanswered, see below answers to the most frequent ones.

Can you power a greenhouse with solar panels?

Solar panels can be a perfect solution for powering a greenhouse for use year-round. If you manage to generate enough electricity using your solar panels, you can even completely offset the electricity used by heaters, fans, and other equipment in your greenhouse.

How much is a solar greenhouse?

A solar greenhouse is the most expensive type of greenhouse to install. The average cost to build a solar greenhouse is between $35 and $45 per square foot. So for a small 50-square-foot greenhouse, the price would likely be around $2000, while a larger greenhouse can easily cost $10,000 or more.

Can a solar panel run a heat lamp?

You can use solar panels to run a heat lamp, and several solar heat lamp kits are available for purchase. Solar heat lamps are commonly used for chicken coops or to keep other animals warm, but they are also ideal for using solar power to heat your greenhouse.

Are there solar-powered greenhouse lights?

If you plan on growing year-round, your plants will benefit from grow lights. You can purchase solar-powered greenhouse light kits. Alternatively, you can buy less expensive LED grow lights and power them using your existing greenhouse solar panels.

How many watts does a greenhouse use?

The amount of electricity required to heat your greenhouse will depend on several factors. Take into account the size of your greenhouse and the climate (the winter temperatures in particular). The typical greenhouse uses an average of one kilowatt-hour (or 1000 watts) of electricity per square foot per year.

Can I buy a greenhouse solar panel kit?

Many different greenhouse solar panel kits are available for purchase for various wattage needs. You can find a 100-watt solar panel kit for just over $150; a 400-watt kit will cost closer to $500.

For a small greenhouse, these kits are an easy and cost-effective way to begin converting your greenhouse to solar power.

Are there greenhouses with solar panels for sale?

If you want to save yourself a lot of the planning and work involved in building a solar-powered greenhouse, you can buy a fully-equipped greenhouse with solar panels. For about $6000, you can buy an 8-foot by 12-foot greenhouse equipped with solar panels, a ventilation system, a watering system, and more.

Are there solar heaters for greenhouses?

You have several options for heating a greenhouse using solar power. You can purchase and install a solar heater kit. Depending on the size of your greenhouse, it may be more cost-effective to buy electric heaters and solar panels to power them separately.

Can I build a greenhouse with a solar panel roof?

Use common sense when installing solar panels for your greenhouse. While the roof is an ideal placement for solar panels, take care not to block too much sunlight from entering your greenhouse.

Depending on the style of greenhouse you have and the number of solar panels you install, roof installation can still be the best option in many cases.

Sources:

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