Greenhouse Heating Options: Electric, Propane & Solar Compared (2026)

Greenhouse Heating Guide: Find the Perfect Warmth for Your Plants

Keeping your greenhouse warm through winter doesn't have to be complicated—or expensive. Let's break down your options so you can choose what works for your space, budget, and growing goals.

Why Greenhouse Heating Matters

Plants need consistent temperatures to thrive. Even cold-hardy greens struggle below 40°F, and tender seedlings need 65-75°F. A properly heated greenhouse:

• Extends your growing season year-round
• Protects plants from frost damage
• Enables seed starting earlier in spring
• Expands what you can grow (tomatoes, peppers, tropicals)

Your Heating Options, Ranked

1. Passive Solar Heating

Best for: Mild climates, budget-conscious growers

• Uses sunlight + thermal mass to trap heat
• Paint containers black, use water jugs, lay stone flooring
• Works naturally during the day; releases heat slowly at night
• Cost: Free (after initial setup)

Our take: Great starter option, but relies on sunshine

2. Electric Space Heaters

Best for: Small to medium greenhouses, convenience seekers

• Plug into standard outlets (for smaller units)
• Look for models with thermostats for automatic control
• Safety tip: Keep away from water, use GFCI outlets
• Cost: $30-150 + electricity

Our take: Easiest to set up and control

3. Propane/Gas Heaters

Best for: Remote greenhouses, no electricity

• Portable, powerful heat output
• Requires proper ventilation (CO2 risk)
• Tank refills needed
• Cost: $100-400 + fuel

Our take: Good for off-grid situations, but monitor air flow

4. Hot Water Heating Systems

Best for: Large greenhouses, long-term installations

• Uses boiler + pipes or solar thermal collectors
• Even, consistent heat distribution
• Higher upfront cost, lower operating costs
• Cost: $500-2000+

Our take: Most efficient for serious year-round growing

5. Compost Heating

Best for: DIY enthusiasts, organic gardeners

• Heat generated by decomposing materials
• Layer straw, manure, kitchen scraps
• Can add significant heat naturally
• Cost: Cheap or free

Our take: Fun experiment, unpredictable results

Sizing It Right

Rule of thumb: You need roughly 1 watt per cubic foot for a 30°F rise above outdoor temp.

Example: 8×12 greenhouse (8ft tall) = 768 cu ft × 1 watt = ~800 watt heater minimum

Add 20% buffer for cold snaps!

Pro Tips

• Insulation first — Bubble wrap walls before adding heat
• Zone heating — Heat just one area for seed starting
• Thermostat control — Saves energy, prevents overheating
• Monitor actual temps — Get a min/max thermometer

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Need proper ventilation too? See our Greenhouse Ventilation Guide.