Choose and set up a greenhouse space heater to protect plants from cold while maintaining a suitable growing temperature. This guide is for greenhouse owners who are new to supplemental heating. It covers heater sizing, placement, safe operation, and temperature checks. Allow 2-4 hours for setup, then monitor the greenhouse over several cold nights.
Get garden gear delivered free with Prime
- Fast, free delivery on millions of items
- Prime Video, Amazon Music and more included
- Member-only deals all year
SmterCon Greenhouse Heater with Digital Thermostat
- ✔ Heat output: 1500 watts
- ✔ Power source: AC/DC (as listed)
- ✔ Amperage: 15 A
VEVOR 1500W Greenhouse Heater with 25° Adjustable Angle
- ✔ Power output: 1500 watts
- ✔ Voltage: 120 volts
- ✔ Amperage: 12.5 A
VEVOR 1500W PTC Greenhouse Heater with Fan
- ✔ Power output: 1500 watts
- ✔ Voltage: 120 volts
- ✔ Amperage: 8.33 A (as listed)
Difficulty: Beginner | Time: 2-4 hours for setup; several nights to check performance
What You’ll Need
Tools & Materials:
- Minimum-maximum thermometer or digital thermometer with a temperature sensor
- Tape measure
- Manufacturer’s heater manual
- Suitable electrical outlet or approved fuel supply, depending on heater type
- Weatherproof extension cord only if the heater manufacturer permits one
Knowledge:
- The lowest temperature your plants can tolerate
- Basic awareness of electrical and fuel-burning appliance safety
Check the heater’s instructions and local electrical and fire-safety requirements before installation. Greenhouses are humid environments; use only equipment approved for those conditions. Keep fuel-burning heaters out of enclosed spaces unless the heater is specifically rated for that use and ventilation requirements are met.
SmterCon Greenhouse Heater with Digital Thermostat
For greenhouse owners who want the heater to respond as conditions change, the digital temperature display and automatic power control give this SmterCon the most decision-ready control setup in the group. Its thermostat is described as maintaining a chosen temperature and switching power automatically, a useful distinction from the VEVOR options, whose supplied details emphasize selectable modes and adjustable direction rather than auto temperature maintenance. That can help reduce constant manual adjustments during routine use.The tradeoff is that its versatility claims do not answer every greenhouse question. The description lists use in patios, garages, and other spaces, but it does not provide dimensions of a recommended greenhouse or a temperature range for the thermostat. Its 1500W output also matches the other two picks, so this is not a more efficient low-draw alternative. A built-in fan may be noisy, and the listed 15A draw makes it especially important to check the circuit and follow the manufacturer’s placement guidance. Choose it for automatic control; choose the lighter VEVOR PTC if frequent relocation matters more.
Pros:
- Digital temperature display makes the setpoint easier to monitor.
- Automatic power control is designed to maintain the chosen temperature.
- Independent overheat protection is specified.
- Pedestal form and adjustable speed offer some flexibility in placement and operation.
Cons:
- The built-in fan may be noisy during greenhouse use.
- At 1500W and a stated 15A draw, it is not a low-demand option.
- The supplied details do not give a thermostat temperature range or coverage area.
Best for: Growers who want a visible temperature readout and automatic on/off control to help maintain a chosen greenhouse temperature.
Not ideal for: Buyers prioritizing a light, quiet heater or those who need a clearly stated thermostat range and greenhouse coverage guidance before choosing.
Bottom line: We rank the SmterCon first for its explicit digital thermostat and automatic control, provided its power draw and fan noise suit the greenhouse.
“We rank the SmterCon first for its explicit digital thermostat and automatic control, provided its power draw and fan noise suit the greenhouse.”
VEVOR 1500W Greenhouse Heater with 25° Adjustable Angle
The standout here is not higher output: this VEVOR is also rated at 1500W. Its advantage is the stated 25° adjustable angle, which gives growers more room to aim airflow toward a working area or away from particularly sensitive plants. It also has heating and fan modes, so it can circulate air without heating when conditions call for airflow. Compared with the smaller VEVOR PTC, its adjustment range is wider, though it is almost twice as heavy according to the listed weights.This model is a practical middle ground for someone who wants a portable heater but expects to position it carefully and leave it in place. Its thermostat range is listed as 40°F to 108°F, providing more concrete setting information than the SmterCon description. However, the maximum setting may not be enough for severe cold or for a poorly insulated space; heater output does not guarantee a particular greenhouse temperature. The 7.1-pound weight also makes it less convenient than the 3.7-pound PTC for regular moves. It specifies IPX4 protection, but that does not remove the need to keep the unit properly placed and follow its instructions around water.
Pros:
- 25° angle adjustment gives more aiming flexibility than the other VEVOR.
- Heating and fan modes support both warming and air circulation.
- Thermostat setting range is specified as 40°F–108°F.
- IPX4 and overheat protection are listed.
Cons:
- Listed weight of 7.1 pounds is the heaviest in this comparison.
- The maximum temperature setting may not meet needs in very cold conditions.
- At 1500W, it still requires attention to circuit capacity and operating cost.
Best for: Growers who want a defined thermostat range, a fan-only mode, and more freedom to angle the heater toward a specific greenhouse zone.
Not ideal for: Anyone who needs a lightweight unit for frequent repositioning or expects one portable heater to overcome severe cold in an uninsulated greenhouse.
Bottom line: We recommend this VEVOR when adjustable heat direction and a stated thermostat range matter more than minimizing weight.
“We recommend this VEVOR when adjustable heat direction and a stated thermostat range matter more than minimizing weight.”
VEVOR 1500W PTC Greenhouse Heater with Fan
When a heater needs to move between a grow tent, flower room, or small greenhouse, this VEVOR is the easiest pick to carry: it is listed at 3.7 pounds and measures 8.27 x 6.3 x 8.66 inches. Its PTC forced-air heating and two power levels are designed to deliver warmth with fan circulation, while the adjustable 15° angle lets us direct output without repositioning the whole unit. Compared with the 25° VEVOR, it gives up some aiming range but is substantially lighter and smaller.We place it third because the supplied specifications are less complete for temperature management. The listing gives a maximum temperature setting of 75°C but does not state a thermostat range or automatic temperature-hold behavior like the SmterCon. A high maximum figure does not tell us how accurately the heater regulates greenhouse temperature, nor does it establish coverage. The fan can also be noticeable in a quiet space. This is best for growers who value portability and straightforward directional heat; buyers relying on automatic setpoint control should favor the SmterCon, while those needing a wider aiming angle should compare the other VEVOR.
Pros:
- At 3.7 pounds, it is the lightest of the three listed heaters.
- Compact dimensions suit smaller grow spaces and storage.
- Two heat levels and fan operation provide basic operating flexibility.
- 15° adjustment and a stable base help direct heat while keeping the unit positioned.
Cons:
- The supplied specs do not describe automatic thermostat control or a setting range.
- Its 15° angle adjustment is narrower than the other VEVOR’s 25° range.
- Fan noise may be noticeable in quiet rooms or enclosed work areas.
Best for: Growers with a compact greenhouse or grow tent who expect to move the heater and value lower weight and smaller dimensions.
Not ideal for: Buyers who need a specified thermostat range, automatic temperature maintenance, or the widest angle adjustment in this lineup.
Bottom line: We choose the compact VEVOR PTC for growers who prioritize easy carrying and small-space placement over automatic thermostat detail.
“We choose the compact VEVOR PTC for growers who prioritize easy carrying and small-space placement over automatic thermostat detail.”
As an Amazon Associate we earn from qualifying purchases.
Before You Start
Decide the temperature you need to maintain overnight. Different plants have different cold limits, so use the needs of the most sensitive plants in the heated area. Heating the entire greenhouse may cost more than protecting a smaller, enclosed section.
Inspect the greenhouse for drafts, gaps, and damaged glazing. Close gaps that can be safely sealed, but do not block required ventilation. A heater cannot reliably compensate for major heat loss, and poor airflow can create uneven temperatures or unsafe conditions.
Step-by-Step Instructions
Step 1: Set a minimum temperature target
Check reliable growing guidance for each plant group and record the lowest temperature they can tolerate. Set the heater thermostat above that limit to allow for sensor variation and cold spots. If you keep plants with different needs, group the most sensitive plants in a smaller protected area.
Tip: Do not use daytime temperature preferences as the overnight minimum. Plants may need different conditions at night.
Check: You have a specific overnight temperature target for the plants in the heated area.
Step 2: Measure the greenhouse
Measure the greenhouse’s length, width, and height, and note the glazing type, insulation, and major gaps. Estimate the volume by multiplying length by width by average height. Use these details with the heater manufacturer’s sizing guidance or a heat-loss calculator to choose a heater rated for the space and your local winter conditions.
Tip: A heater’s wattage or fuel rating alone does not show whether it can keep your greenhouse warm. Heat loss depends on outdoor temperatures, glazing, drafts, and the temperature you need inside.
Check: You have compared your greenhouse conditions with the heater’s stated capacity and selected a model suited to the coldest conditions you expect.
Step 3: Choose a suitable heater
Select an electric, propane, natural-gas, or other heater only if its instructions approve it for greenhouse use. Confirm its capacity, thermostat range, safety shutoffs, and required clearance. For an electric heater, check that the circuit can handle its load; ask a qualified electrician if you are unsure. For a fuel-burning model, follow the manual’s rules for ventilation, exhaust, fuel storage, and carbon-monoxide protection.
Tip: Do not use an indoor household heater, open-flame heater, or improvised fuel appliance in a greenhouse unless its manufacturer specifically approves that setting.
Check: The heater is approved for the environment and fuel or electrical supply, and you can meet all clearance and ventilation instructions.
Step 4: Prepare a safe location
Choose a stable, dry, level position that follows the manufacturer’s clearance distances. Keep the heater away from leaves, potting materials, plastic film, water sources, walkways, and stored fuel. Place it where plants will not touch it and where air can circulate around its intake and outlet. Secure it against tipping if the manual calls for it.
Tip: Do not aim hot airflow directly at foliage or seed trays. Localized heat can dry or scorch plants while other parts of the greenhouse remain cold.
Check: The heater stands securely, its required clearances are open, and its airflow will not blow directly onto plants.
Step 5: Connect power or fuel as directed
Follow the heater manual to connect the appliance. Use a properly rated, grounded, weather-protected outlet for electric models, and keep plugs and connections away from wet floors and condensation. Avoid daisy-chained power strips and undersized cords. For fuel-burning heaters, connect only approved fuel lines and fittings, check for leaks using the method specified by the manufacturer, and keep cylinders or fuel storage at the required distance.
Tip: If a circuit breaker trips, a plug becomes hot, you smell fuel, or a connection appears damaged, stop and address the fault before operating the heater.
Check: Connections match the manual, remain dry and undamaged, and show no signs of overheating or fuel leakage.
Step 6: Position and check the thermostat sensor
Place the thermostat sensor at plant height in the part of the greenhouse you need to protect. Keep it away from the heater’s direct airflow, cold glazing, direct sunlight, and damp surfaces. If the sensor is built into the heater, position the appliance according to its manual and use a separate thermometer to check temperatures elsewhere.
Tip: A sensor beside the heater can read warmer than the plants at the far end, causing the heater to switch off too soon.
Check: The sensor measures the plants’ surroundings rather than a concentrated hot or cold spot.
Step 7: Set the thermostat and safety controls
Set the thermostat to the target temperature you recorded, then confirm that any built-in overheat, tip-over, and flame-failure protections are enabled. Follow the manual for first-use startup and keep access to the shutoff control clear. Do not disable a safety feature to prevent nuisance shutdowns.
Tip: Avoid repeatedly adjusting the setting during the first heating cycle; give the greenhouse time to respond before changing it.
Check: The heater starts and stops according to its controls, and its safety features remain active.
Step 8: Monitor a full heating cycle
Run the heater while you can observe it, then check thermometer readings at plant height in several locations. Record the lowest overnight temperature and compare it with your target. Check again on a colder night, since a mild evening does not show whether the heater can handle winter conditions.
Tip: Keep required vents open for fuel-burning appliances even if that means using a heater with more capacity. Never trade required ventilation for warmth.
Check: Temperatures remain within the plants’ safe range across the protected area, with no overheating, unusual smell, smoke, or repeated shutdowns.
Step 9: Adjust the setup if readings vary
If readings are too low, check for drafts, blocked airflow, poor sensor placement, or a heater that is undersized for the conditions. Make safe adjustments allowed by the manual, such as improving greenhouse insulation or moving plants into a smaller protected zone. If temperatures are uneven, improve air circulation with equipment suitable for the greenhouse and keep its airflow from directly striking plants.
Tip: Do not place a heater closer to plants or materials than its stated clearance to solve a cold spot.
Check: Repeat overnight readings show temperatures within the target range at the coldest plant locations.
Common Mistakes to Avoid
- Running a fuel-burning heater without the ventilation or exhaust required by its manual. — Follow the approved installation and ventilation instructions, and use suitable carbon-monoxide protection where required.
Troubleshooting
Problem: There is a fuel smell, smoke, unusual noise, or a carbon-monoxide alarm sounds.
Solution:
Leave the greenhouse and follow the appliance’s emergency instructions. Shut off the fuel only if you can do so safely. Do not restart the heater until a qualified professional has inspected it and identified the cause.
What Success Looks Like
Your heater is approved for greenhouse use, installed with the required clearances and connections, and controlled by a sensor that reflects conditions at plant height. Thermometer readings across the protected area stay within the target range on cold nights. The heater runs without repeated shutdowns, overheating, fuel odors, smoke, or other signs of a fault.
Next Steps
Check the thermometer each morning during cold weather and record the overnight low. Inspect the heater, plugs, cords, fuel fittings, and surrounding clearances regularly, following the maintenance schedule in its manual. Recheck the setup when you add plants, change the protected area, or experience colder weather. Arrange professional service if the heater behaves inconsistently or shows signs of damage.
Frequently Asked Questions
What temperature should I set a greenhouse heater to?
Use the lowest safe overnight temperature for the most sensitive plants in the heated area, based on reliable growing guidance. Place a separate thermometer at plant height to check whether the setting matches conditions where the plants are.
Can I use a regular space heater in a greenhouse?
Use a regular space heater only if its manufacturer approves it for a humid greenhouse environment. Check its electrical requirements, clearances, and safety features. Do not assume an indoor-rated heater is suitable around condensation and water.
Is an electric or gas greenhouse heater better?
The right option depends on greenhouse size, available power or fuel, local costs, ventilation needs, and heater capacity. Compare models using their approved use, operating requirements, safety features, and performance in your expected winter conditions.
How can I tell whether my greenhouse heater is large enough?
Monitor temperatures at plant height in several locations during cold nights, including nights near your area’s winter lows. If the coldest locations fall below the plant target despite correct setup and reduced heat loss, consult the manufacturer’s sizing guidance for a higher-capacity model.
