Products and configurations to compare
High-current greenhouse thermostat rated for 1500W+
Buy by current/watt rating before app features.
Best when: you use a standard 1,500W greenhouse heater
Watch for: verify continuous resistive-load rating and enclosure suitability
INKBIRD ITC-308
Current ITC-308 supports separate heat and cooling outlets and compressor delay.
Best when: your connected heating/cooling loads stay within 1,200W total at 120V
Watch for: not appropriate for a 1500W heater at 120V
Heater with integrated greenhouse thermostat
Best when heater placement is central and calibration is acceptable.
Best when: you prefer one appliance and minimal wiring
Watch for: sensor location may represent heater area rather than canopy
Probe location is the external controller advantage
It can measure plant-zone temperature away from the heater.
Load rating is non-negotiable
Do not use a 10A/1200W controller for a 1500W heater.
Dual-stage control is useful for seasons
One controller can heat below a threshold and exhaust above another when loads are within rating.
Built-in control has fewer failure points
Fewer plugs, cords and sensors can be valuable in humid spaces.
Use independent min/max monitoring
A second thermometer/logger helps catch a failed thermostat.
Controllers only work as well as sensor placement
A temperature probe on a sunny metal frame reads something different from plant-canopy air. Hang probes in shaded moving air near the crop zone and away from heater discharge, wet media and cold glazing. The same rule applies to humidity/VPD sensors.
Simple plug-in thermostats are excellent when the job is binary: heater on below X, fan on above Y. Multi-device controllers become useful when lights, exhaust, circulation and humidification need coordinated triggers. Complexity should buy better control, not merely a prettier app.
Electrical ratings are hard limits
A controller rated for 1,200W total should not directly switch a 1,500W heater. Use only devices within voltage/current ratings and follow code/manufacturer requirements. Greenhouses are humid environments, so GFCI protection and weather-appropriate enclosures/connectors matter.
Before checkout
- Greenhouse dimensions and approximate volume are measured
- Climate goal is frost-free, cool-season or warm-crop winter growing
- Electrical circuit capacity and GFCI protection are confirmed
- Controller output rating exceeds connected load
- Ventilation has a real intake path, not only an exhaust fan
- Irrigation pressure/filtering matches emitters and tubing
- Light footprint matches the actual bench/canopy
- Seasonal materials can be removed or adjusted
- Replacement parts and consumables are available
- Automation can be overridden manually during a failure
The right upgrade solves the limiting factor
Greenhouses tempt owners to buy equipment one category at a time, but climate is a system. A bigger heater can be wasted through unsealed glazing. A giant exhaust fan can accomplish little without intake area. Perfect drip irrigation can still fail if the filter clogs. Before ordering, identify the variable that is actually leaving the safe crop range: overnight minimum temperature, afternoon maximum, humidity, root-zone moisture or daily light.
Spend first on measurement and failure prevention. A min/max logger, independent thermometer, pressure regulator or simple flow check can reveal that the existing equipment is adequate but badly controlled.
Commissioning the system
Test every automated device before plants depend on it. Force the thermostat above and below setpoint, manually trigger irrigation zones, watch an automatic vent through a warm day, simulate a power interruption where safe, and verify that fans have real intake air. Record the first week of minimum and maximum temperature/humidity so settings can be adjusted from evidence.
Greenhouse systems should also fail manually. Know which plug, valve or vent to operate if the controller loses Wi-Fi, a sensor breaks or a timer sticks. Simpler recovery is more valuable than another dashboard.
Frequently asked questions
Can ITC-308 control a 1500W heater?
Its current 120V spec is 10A / 1200W total, so not directly.
Why is external probe better?
It can be placed where the crop is rather than beside the heater.
Do I need Wi-Fi?
No. Wi-Fi is convenience for alerts/remote visibility, not core thermostat function.
Can one controller heat and cool?
Dual-stage models such as ITC-308 can, within their electrical ratings.
Current product/source checks
Affiliate disclosure: GreenhouseGuide.co may earn from qualifying purchases through Amazon Associates and eBay Partner Network at no extra cost to you. Amazon links use scouttheory-20; eBay links use campaign 5339137014.