Best Greenhouse Heaters

The Bio Green Palma 110V is the best greenhouse heater for most hobby growers because it combines a digital thermostat, a splash-proof IPX4 housing, and a fan in a compact 1,500-watt unit, the Dr. Infrared DR-218 is the best budget electric option, and the Mr. Heater 18,000 BTU Propane Cabinet Heater is the best choice for a greenhouse with no power, as long as you ventilate it properly. The right heater depends on how much heat your structure loses, not on how big the greenhouse looks.

Most buyers choose by wattage on the box. That is the wrong starting point. A greenhouse loses heat through its covering, and the covering matters more than floor area. A twin-wall polycarbonate house can be kept at 45 degrees F with half the heat of a single-layer film house. This guide explains how to size a heater, compares electric and propane options on the specs that count, and ends with the safety rules that keep plants and people safe.

Our top picks

Top pickVEVOR Greenhouse Heater

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Also greatPasapair Greenhouse Heater with Thermostat

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Also greatVEVOR Greenhouse Heater with Thermostat

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Also greatVEVOR Greenhouse Heater

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Quick picks

How we chose

This guide is research-based. We compared manufacturer specifications and the published findings of several buying guides, and we cross-checked outputs, coverage ratings, safety features, and thermostat ranges. Where a spec was not available we say so. Nothing here describes our own use of any heater. We favored three criteria in order: safe operation in humid, dusty, damp conditions; accurate temperature control; and fit to realistic heat loss.

• Splash and moisture protection: greenhouses are damp. An IPX4 rating means the unit tolerates splashing water.
• Thermostat quality: a digital thermostat holds a tight range. A manual dial usually needs checking with a separate thermometer.
• Safety shutoffs: tip-over and overheat shutoffs are the minimum. Gas units also need an oxygen depletion sensor.
• Heat distribution: a fan moves warmed air to plant height and prevents hot and cold pockets.
• Fuel and power access: electric is clean and controllable. Propane works without a power supply.

Step one: size the heater to your heat loss

Heat loss in BTU per hour equals the covered surface area times the temperature difference times a heat-loss factor (U-value) for the covering. Typical factors people use are roughly 1.2 for single-layer polyethylene film, and roughly 0.7 for twin-wall polycarbonate or double film. Treat these as planning numbers, since actual values vary by product and installation.

Worked example: an 8 ft by 10 ft hobby greenhouse

1. Assume the walls and roof total about 260 square feet of covering.
2. Set a target: keep the inside at 50 degrees F when the outside drops to 20 degrees F. The difference is 30 degrees.
3. Single-layer film: 260 times 30 times 1.2 equals about 9,360 BTU per hour.
4. Twin-wall polycarbonate: 260 times 30 times 0.7 equals about 5,460 BTU per hour.
5. Convert to watts for electric: one watt equals about 3.412 BTU per hour. So 9,360 BTU is about 2,740 W, and 5,460 BTU is about 1,600 W.
6. Add a margin of 10 to 20 percent for wind and door openings.

The result: a single 1,500 W heater is only marginal in the twin-wall house and clearly undersized in the film-covered house at a 30-degree drop. Either run two units, step the target down to a frost-protection temperature of about 40 degrees F, or move to a larger heater. If your lows are only 10 degrees below your target, the same house needs only a third of that heat. The model says: measure your coldest expected temperature difference first, then buy.

Electric versus propane

Product reviews

Bio Green Palma 110V Greenhouse Heater

Spec line: Electric · 1,500 W (about 5,120 BTU) with a lower 750 W setting · rated for 130 sq ft · digital thermostat 0 to 90 F · IPX4 splash-proof · overheat auto-shutoff · fan-only mode · 6 ft cord

The most consistently recommended small greenhouse heater. The digital thermostat is the key advantage, since it holds a steady temperature instead of cycling by feel. The fan circulates air, and the carry handle makes it easy to move.

Best for: Hobby houses up to about 130 sq ft with good insulation.

Skip if: Your greenhouse is a single-layer film structure in a very cold zone, or the outlet is far away, since the cord is short.

• Pros: digital controls, splash-proof, strong air circulation, compact, fan-only mode for summer air movement.
• Cons: relatively short 6 ft power cord; 1,500 W limits it in large or leaky structures.

Dr. Infrared Heater DR-218

Spec line: Electric · 1,500 W (about 5,200 BTU) · rated for 150 sq ft · manual dial thermostat · IPX4 splash-proof · cool-touch housing · overheat shutoff · built-in fan

A budget-friendly alternative with similar output. The trade is control: a manual dial must be calibrated against an external thermometer, so place a min-max thermometer at plant height and adjust the dial until it matches.

Best for: Budget-minded growers who are willing to calibrate.

Skip if: You want to set a temperature and forget it.

• Pros: low cost, simple operation, fan, several safety features.
• Cons: thermostat needs calibration.

Vornado Whole-Room Heater with Auto Climate

Spec line: Electric · 1,500 W (about 5,118 BTU) · rated for 250 sq ft · digital display · remote · timer · tip-over and overheat shutoff · not splash-proof

A strong indoor heater with good air movement and a remote. It is not designed for greenhouse humidity, so only consider it for a dry, enclosed space such as an attached sunroom, a potting shed, or a well-sealed structure. In a damp greenhouse, choose a splash-rated unit.

Best for: Dry, sheltered spaces such as potting sheds.

Skip if: Water can splash or mist reaches the heater.

• Pros: vortex air circulation, remote, timer, digital control.
• Cons: not splash-proof, not purpose-built for greenhouses.

Dr. Infrared Heater DR-975 7,500-Watt

Spec line: Electric hardwired · 7,500 W (about 25,597 BTU) · remote-controlled thermostat 50 to 90 F · low and high modes · timer · wall or ceiling mount · adjustable louvers

A heavy-duty unit for larger or leakier structures. It needs professional hardwiring and mounting, and a dedicated circuit that suits its draw. A heater this size also needs an electrician to confirm wiring and breaker capacity.

Best for: Larger greenhouses where a plug-in unit is too small.

Skip if: You rent, or you cannot bring in a dedicated circuit.

• Pros: high output, remote thermostat, mount options, timer.
• Cons: requires professional installation and hardwiring.

Comfort Zone Ceiling-Mounted 5,000-Watt Heater

Spec line: Electric hardwired · 5,000 W (about 17,065 BTU) · fan-forced · ceiling mount · no thermostat on the unit · heavy-duty construction

A rugged ceiling-mounted fan heater that keeps floor space clear. It has no onboard thermostat, so pair it with an external controller that matches its rating. Like the DR-975 it requires professional hardwiring.

Best for: Workshop-style greenhouses with an existing controller.

Skip if: You want built-in temperature control.

• Pros: strong output, clears the floor, rugged.
• Cons: no remote thermostat, professional installation required.

Mr. Heater 18,000 BTU Propane Cabinet Heater

Spec line: Propane · 6,000 to 18,000 BTU adjustable · rated for 450 sq ft · three heat settings · tip-over shutoff · low-oxygen shutoff · piezo igniter · casters · no thermostat · no fan

An off-grid option with directed radiant heat. Without a fan, warmth radiates in front of the unit rather than circulating, so position it carefully. Because it burns fuel inside the structure, ventilation is not optional. See the safety section.

Best for: Greenhouses without electricity, or as a backup during outages.

Skip if: You cannot ventilate the structure or want thermostat control.

• Pros: no electricity required, portable, three heat levels, safety shutoffs.
• Cons: no thermostat, needs propane refills, no fan.

Mr. Heater Buddy (MH9BX)

Spec line: Propane · 4,000 to 9,000 BTU · runs on a 1 lb cylinder, or a larger tank with a hose · oxygen depletion sensor · tip-over shutoff

A small, portable propane heater that can take the edge off a frost in a compact structure. Output is modest, so it suits a small, well-insulated house or a short cold snap, not a whole winter of use.

Best for: Emergency frost protection in a small house.

Skip if: You need steady, thermostat-controlled heat.

• Pros: portable, small, low output suits a small space, safety sensors.
• Cons: no thermostat, small cylinders run out quickly, moisture and combustion gases.

Vivosun Seedling Heat Mat and Digital Thermostat

Spec line: Electric · covers about 6.9 sq ft · digital thermostat · waterproof · double PVC insulation · flame-retardant surface

Not a space heater. A heat mat warms the root zone of seedlings, which often raises soil temperature by 10 to 20 degrees F. It will not protect foliage from frost, so use it as a complement to a space heater, not a replacement.

Best for: Starting seedlings and cuttings in a cool greenhouse.

Skip if: You need to protect established plants from freezing air.

• Pros: low power use, precise bottom heat, waterproof.
• Cons: does not heat the air, ineffective in deep cold.

Spec comparison

Decision matrix

Safety rules that matter

Electric heaters

• Plug into a ground-fault protected outlet. Damp spaces and electricity are a shock hazard.
• Avoid daisy-chained or undersized extension cords. A 1,500 W heater draws about 12.5 amps at 120 volts, so use a heavy-duty outdoor-rated cord only if you must, keep it short, and never coil it while in use.
• Keep the heater clear of plants, plastic sheeting, and cardboard. Leave the clearances in the manual.
• Mount or place it where watering cannot reach it.

Propane and other fuel-fired heaters

• Burning fuel produces carbon monoxide, water vapor, and other combustion gases. Provide fresh-air ventilation for as long as the heater runs, and do not seal the greenhouse.
• An oxygen depletion sensor is a safeguard, not a carbon monoxide alarm. Add a battery-powered carbon monoxide alarm that is rated for the space.
• Combustion gases and excess humidity can also harm plants and promote mold, so ventilation helps both people and crops.
• Look for tip-over shutoff, a flame-failure or low-oxygen shutoff, and follow the manufacturer on indoor-safe use.
• Store cylinders upright, outdoors, and away from heat. Never leave a fuel-fired heater running unattended overnight in a closed space.
• Keep a fire extinguisher nearby.

Reduce the heat you need

• Seal gaps around doors and vents with weatherstripping.
• Add a second layer of bubble film or twin-wall panels to the north side.
• Place water barrels inside. Water stores heat during the day and releases it at night.
• Use thermal curtains over plants at night in extreme cold.
• Grow plants appropriate to your goal. Frost protection at about 35 to 40 degrees F needs far less energy than a tropical 60 degrees F.

FAQ

What size heater do I need for a small greenhouse?

Calculate heat loss: covered surface area times temperature rise times the covering factor. For an 8 ft by 10 ft house with twin-wall panels and a 30-degree rise, expect roughly 5,500 BTU per hour.

That is about 1,600 watts. Add a margin, or lower your target temperature to reduce the demand.

Are electric or propane greenhouse heaters better?

Electric heaters add no fumes or moisture and usually offer better thermostat control. Propane works without power and suits off-grid sites.

For most hobby growers with power, electric is the safer, simpler choice. Use propane as a backup or where electricity is unavailable.

Can I use a propane heater in a closed greenhouse?

Only with ventilation. Propane combustion releases carbon monoxide and water vapor that can build up in a sealed space.

Provide a fresh-air opening, use a carbon monoxide alarm, and follow the manufacturer’s instructions for the specific heater.

What temperature should I keep a greenhouse at in winter?

It depends on the plants. Frost protection for hardy crops needs about 35 to 40 degrees F, while tender plants need higher temperatures.

Pick the lowest safe target for your plants, because every extra degree raises energy use.

Is a heater with a built-in fan better?

Usually yes. A fan moves warm air to plant height and evens out temperature, which reduces cold spots and condensation.

A fan also supports summer use, since many greenhouse heaters offer a fan-only mode for air movement.

Is it safe to use a regular indoor heater in a greenhouse?

Only if it is dry and protected. Many indoor heaters are not splash-rated, and greenhouse humidity and watering can damage them.

Choose an IPX4-rated unit made for damp spaces, and keep it well away from water and plants.

How can I cut greenhouse heating needs?

Reduce heat loss first. Seal gaps, add insulation, use thermal mass, and lower the target temperature.

Water barrels, a second glazing layer, and night curtains can cut the heater runtime and spread the load.

Do I need a thermostat on a greenhouse heater?

Yes, for most uses. Without one, a heater runs continuously and can overheat plants or waste energy.

If your heater has no thermostat, add an external plug-in thermostat rated for the heater load, or keep a thermometer inside and check it often.