Set 45°F. It Holds 45°F All Night.
Five reasons growers who've watched a "MIN to MAX" heater run blind all winter are switching to the one that reads the temperature beside their plants — and shuts off the moment it gets there.
The Knob Says MIN to MAX. That's a Power Setting, Not a Temperature.
Look at the knob on the heater you own right now. There's no 40, no 45, no 50 on it. There's MIN, there's MAX, and a guess in between. That knob tells the heater how hard to run. It never tells it when to stop.
So you turn it to the middle at 9pm and hope. If the night is mild, it cooks the greenhouse and runs up the bill. If the cold comes harder than the forecast said, "medium" isn't enough and the tray goes black by morning. One verified buyer summed up those dial heaters in five words: "On or off, no in between."
FrostGuard swaps the guess for a number. The digital thermostat comes in the box. You press SET, pick 45°F, and that's the instruction the heater follows all night.
Here's Exactly What Happens When You Set 45.
No magic, just a loop that runs all night without you. The probe reads the air beside your plants every few seconds. The thermostat compares that reading to your number and flips the heater on or off.
| Probe reads | Heater does | You do |
|---|---|---|
| Below 45°F | Fires. Full heat in about 3 seconds, fan pushes it across the bench. | Sleep. |
| Hits 45°F | Shuts off and waits. No power drawn. | Sleep. |
| Drops again | Fires again, automatically, as many times as the night needs. | Sleep. |
| Sunrise | Greenhouse warms on its own, heater stays off. | Check the display over coffee. |
That's the whole difference. A knob heater runs one setting for eight hours. FrostGuard runs only when the reading says it has to. Set 45 tonight. It holds 45 until morning.
It Reads 45 Where Your Plants Are. Not at the Roof.
Warm air rises. In a small greenhouse on a cold night, the peak runs several degrees warmer than the bench, and the bench is where your seedlings are. A thermometer hanging from the roof frame tells you the greenhouse is fine while the trays are freezing.
Built-in heater thermostats have the same blind spot, only worse. Their sensor sits inches from their own hot element, so it reads warm air the heater just made and shuts off early.
FrostGuard's probe sits on a cable, away from the heater. Push it into the soil beside the seedlings, clip it to the bench, or hang it by the roost. Whatever it reads is what the heater answers to. So when the display says 45, it means 45 where it counts.
Why 45? And What to Set Instead.
45°F is where most growers land because it keeps frost well away from the leaves without paying to heat a greenhouse like a living room. But it's your number, and the controller takes anything from 40 to 108. Common starting points:
| What you're protecting | Starting setting |
|---|---|
| Overwintering figs, citrus, geraniums, tender perennials | 40–45°F |
| Cool-season seedlings lettuce, brassicas, onions | 45–50°F |
| Warm-season starts tomatoes, peppers | 55°F+ |
| Coop keeping waterers from freezing | 40°F |
| Garage or shed tools, paint, a workbench | 50°F |
Starting points, not rules. Every degree you add is more run time, so start low and nudge it up if the plants ask for it. The point is that you're choosing a number at all. The knob never let you.
It Only Costs Money While It's Below Your Number. $79.95, Thermostat Included.
A knob heater draws power from the minute you turn it on to the minute you walk out and turn it off. FrostGuard draws power only while the probe reads below your setting. On a typical frost night that's a few hours of actual run time, not eight.
The numbers: 1500W / 5100 BTU on high, 800W for milder nights, fan-only for summer. On 800W at the US average of about 17¢ per kWh, that's roughly 14¢ an hour, and only for the hours it's actually firing. Compare that to one lost tray of February starts, and the whole season they were supposed to become.
$79.95 during the Fall Sale, down from $159.90, with free shipping. Straight answer on size: it's a frost-protection heater for a small greenhouse, a coop, a sunroom, a grow tent or a one-car garage. Bigger or draftier space? Two units, two probes, two numbers.
A 1500W PTC ceramic greenhouse heater that ships with a digital thermostat and probe. You pick the number. It holds the number. All night, without the knob, without the guess, without the 2am walk.
Why 50% off? It's our Fall Sale, priced for growers who want the thermostat set and the probe placed before the first hard frost, not the night of it.
$79.95 during the Fall Sale, half off with free shipping and 30 nights to change your mind. A thermostat in the box, a probe that reads beside your plants, and a heater that fires below your number and stops at it.
Get FrostGuard — 50% Off →