The 8 Best Greenhouse Heaters of 2026

Before you judge this heater, go look at the outlet. It's a 3,000-watt, 240-volt unit drawing 12.5 amps, which means a dedicated circuit of the kind a dryer or a welder uses. Most hobby greenhouses have 120-volt service only, and running a new line will cost more than the heater does. If the circuit is already there, this is the most heat you can put into a house for the money.

What the power buys is radiant heat with a fan behind it, IPX4 splash protection for a building that gets hosed down and drips all winter, a claimed 600 square feet of coverage, and a heavy-gauge steel frame that won't walk across the floor in wind. We were struck by how solid it feels for the price: small enough to tuck into a corner at 10 by 10 by 13 inches, heavy enough at 13 pounds to stay put. Eight-by-sixteen houses in hard freezes are exactly what it was designed for.

The dial is the compromise. Nothing on it is numbered — low to high, plus a three-speed fan — so you tune by watching a thermometer rather than setting a figure and walking away. Longevity is uneven as well: some of these run for several winters and some quit inside two months, so keep the receipt and the one-year parts warranty where you can find them, and check the fan and cord at the start of each season.

Dollar for dollar, this is the easiest one on the page to say yes to. It's the least expensive 1,500-watt heater in this group that carries an ETL listing, and the listing is the part we care about: it means an independent lab has looked at the wiring and the overheat cutout rather than only the marketing copy. For a small hobby house, that's the difference between a bargain and a gamble.

At 3.3 pounds with a built-in handle, it moves from greenhouse to garage in one hand, and the head tilts 90 degrees so you can aim warm air down a path instead of into a bench of seedlings. Three modes cover a mild night and a hard freeze in the same week, and the ceramic element reaches temperature in about three seconds, so there's none of the slow build you get from an oil-filled radiator.

The knob is the catch, and so is the size. There's no number to set, so mark your spot with a paint pen and keep a thermometer at bench height. And the honest ceiling is the volume of the house: in a tight six-by-eight it warms quickly and holds, while a ten-by-sixteen in January will have it running all night and still losing ground.

The night the forecast drops twelve degrees is the night this heater earns its keep. Kiroto's unit pairs with the Smart Life app over Wi-Fi, so the greenhouse temperature sits on your phone instead of on a thermometer you have to walk out and squint at. You can nudge the setpoint from the kitchen, put it on a 24-hour timer, or get an alert when the house drifts toward 40°F. That's the difference between a 2 a.m. trip across wet grass and a glance at a screen.

The hardware underneath is ordinary in a good way: 1,500 watts, a 41 to 113°F range, a 70-degree oscillation that sweeps warmth across a bench rather than into one pot, and a fan-only mode for July. At 8 pounds and roughly shoebox-sized, it sits on a shelf or the floor without eating bench space, and the swing keeps a small house from ending up with one baked corner and one cold one.

What we can't promise is the connection. Greenhouses are usually the worst-covered corner of a property, and a metal frame between the router and the unit doesn't help. Set the thermostat on the unit itself first so it runs correctly with or without the app, then add the phone. It's also the priciest corded heater in this group, which is the honest trade for remote control.

A little over eight inches tall and under three pounds, this is the smallest heater here, and it's built to a price. What the price buys is real: a 1,500-watt PTC element, high and low heat plus a fan, a 40-degree manual tilt, an overheat shutoff, and a cold-rolled steel housing on a grippy base. For a well house, a cold frame, or a shed you're only trying to keep above freezing, that's most of what you need and nothing you don't.

Our favorite use for it is as a second heater. It's small enough to sit on a shelf above a germination tray, light enough to move with two fingers, and the tilt earns its keep in a way the specification doesn't convey: aim the warm air along the floor and let it rise instead of blasting a bench point-blank. We'd rather have two of these at either end of a shed than one big unit in the middle.

The savings surface in the thermostat. It's a dial with no numbers, and it doesn't hold a mark with much precision — some units cycle more or less where you set them, others run right past it. Set it low, put a thermometer where the plants are, and if it won't shut off at all, return it rather than living with it. Keep the space small, too; a ten-by-ten in a cold snap is more than this one can hold.

Seven hundred watts is less than half what most of this list puts out, and that's the first thing to understand about it. A four-by-four grow tent holds heat like a cooler; a glass greenhouse in January does not. VIVOSUN built this for the tent, and in that setting the control is genuinely good.

Five heat levels run on PWM, a high-precision sensor tracks the space in real time, and the thermostat can work to VPD — the vapor-pressure deficit that tells you whether your plants are transpiring comfortably — rather than to temperature alone. That's a more useful target than it sounds, because a heater chasing a number while ignoring humidity will dry a tent out doing it. Set it on the unit or through the app and it holds within a couple of degrees without short-cycling all night.

The housing is V0 flame-retardant with tip-over and overheat protection, the fan is quiet enough to forget about, and the footprint disappears into a corner. Where it falls short is exactly where you'd expect: put it in an unheated outbuilding on a twenty-degree night and 700 watts goes nowhere. Treat the wattage as the boundary of the product rather than a flaw in it.

A 160 cm flexible hose is the reason to look at this one. Instead of dumping warm air out of a grille in the corner, the SF lets you run the heat to the other end of the tent, and a sensor on an RJ12 cable reads temperature at the canopy rather than inside the heater's own shell. If you've ever cooked the plants nearest a heater while the far side stayed cold, that combination is the fix.

Underneath the plumbing it's a 530-watt PTC unit with ten levels of heat and ten of fan speed, a 32 to 140°F range, a 24-hour timer, and a three-degree dead zone so it isn't chasing its own setpoint every few minutes. Multiple overheat protections sit on top of that. We were also pleased by how gentle the output is — the air arriving at the plants is warm rather than harsh, which matters when it's aimed at leaves for hours.

The catch is the wattage, the lowest here by a wide margin. It's a small-tent heater, full stop: a cold snap will outrun it in a big setup or a cold-climate garage, and no amount of clever control fixes that. Setup asks more of you than the rest, too — a controller, a sensor cable, a hose, and a timer to configure before it does anything useful — so give it an evening rather than ten minutes.

Milkhouse heaters have been warming pump houses and garages for decades, and this is that shape: a 15.8-inch steel column with a handle on top and a fan inside. The metal body is what we appreciate in a greenhouse, because it doesn't mind condensation the way a plastic-housed ceramic unit does, and it stands on the floor where the cold air actually pools instead of occupying bench space.

The numbers are ordinary and adequate: 1,500 watts on high, 1,300 on low, a fan-only setting, a rotary thermostat, tip-over and overheat cutouts, and a three-prong plug — a detail we noticed because plenty of cheap utility heaters still ship with two. The 200-square-foot rating is optimistic for an unheated glass house but believable for a garage, a barn aisle, or a well-insulated shed.

Two things to weigh before you buy. The rotary dial carries no markings, so you'll set it against a thermometer and mark the spot yourself. And the record here is uneven in a way that matters for something running unattended overnight: some units quit within a few months, and the housing has smoked on others. Put it on a GFCI outlet, keep it clear of plastic pots and shade cloth, and check on it in person now and then rather than trusting it blind.