Heat Pack. is the thermal engine behind the Seed Starter system — a USB-C powered heater that holds any temperature between 20°C and 35°C, adjustable in 1°C steps, for as long as you leave it running. Unlike a traditional heat mat, which warms a wide area at whatever fixed output it was built for, Heat Pack. concentrates warmth into a small controlled zone and holds it to a number you choose. It's sold on its own here for growers who already own a Sprout. skin, need a second unit to run germinations in parallel, or are buying into the system via GermiPad. Starting from scratch? The Sprout. + Heat Pack. Kit gets you this unit plus the silicone chamber for $159.95 — $9.95 less than buying the two separately.
20–35°C
adjustable in 1°C steps
6 W / 1 W
warm-up / holding temperature
USB-C
runs off a standard phone charger
AU/NZ stock
official distributor, local warranty
Precise warmth instead of approximate warmth
A conventional propagation mat has one setting: on. It puts out a fixed amount of heat across its whole surface, and what your seeds actually experience depends on the room, the tray, and what else is stacked on it. Heat Pack. inverts that. You set a target temperature, and it holds that target in a small, insulated zone.
That precision matters most in Australian conditions. Ambient temperatures rarely sit still inside germination range — overnight lows drop out of it in most of the country for much of the year, and a spare room in winter never gets near it. Seeds that would otherwise take weeks longer, germinate patchily, or fail outright get a stable environment instead of a fluctuating one.
Set it once and it remembers. Power the unit off and back on and it returns to your last saved temperature automatically, so a knocked cable or a power cut doesn't reset your germination run.
One engine, several germination formats
Heat Pack. is designed to be used interchangeably across Seed Starter's silicone skins. Buy it once and you own the powered part of the system permanently — adding a new germination format later means buying a skin, not a whole new device.
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Sprout. — silicone germination chamber, one pod holding as many seeds as you care to fit. Available now, or as a matched kit with Heat Pack.
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GermiPad. — a propagation platform for the stage after sprouting, with an aluminium heat-distribution plate and adjustable humidity dome. Landing in Australia shortly, and sold standalone because it's built to run on the Heat Pack. you already own. Buy a Heat Pack. now and it will drive both Sprout. for germination and GermiPad. for the seedling stage — one heater, the whole early life of the plant.
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Germinator Mini. — coming to Australia.
It also runs at a genuinely trivial power draw: about 6 W while warming up, roughly 1 W to maintain temperature. That's one of the lowest-consumption germination heaters on the Australian market, and low enough that leaving it on for a full multi-week cycle costs next to nothing.
Sold on its own. This listing is the Heat Pack. only — no silicone skin is included. If you're starting from scratch and want single-seed germination, the
Sprout. + Heat Pack. Kit is better value. Buy this on its own if you already have a skin, want a second unit for parallel runs, or are pairing it with GermiPad.
You'll also need: a USB-C wall adapter — 5 V, minimum 1.5 A, 20 W or higher recommended. Not included; most modern phone chargers work.
Setting the temperature
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Connect. Plug Heat Pack. into a USB-C adapter (5 V, minimum 1.5 A; 20 W or higher recommended).
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Adjust. Use the + and − buttons via the rear control ports, pressed with the small key included in the box. Each press moves the target by 1°C, anywhere from 20°C to 35°C.
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Confirm. The indicator light flashes with each adjustment and confirms when the new setting is saved.
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Fit a skin. Sit Sprout. — or another compatible Seed Starter skin — on top.
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Leave it. Heat Pack. holds the set temperature for the entire germination cycle and resumes it after any power interruption.
FAQ
Should I buy this on its own or get the kit?
If you don't already own a Sprout. skin, get the kit — it's $159.95 against $169.90 for the two bought separately, and you get a matched pair. Buy the Heat Pack. alone if you already have a skin, need a second unit to run germinations in parallel, or are pairing it with GermiPad, which is sold without a heater on purpose.
How is this different from a normal heat mat?
A heat mat warms a broad area at a fixed output you can't set. Heat Pack. holds a specific temperature you choose, in 1°C increments, inside a small insulated zone. It also draws around 1 W to maintain that temperature, against tens of watts for a typical mat. Different tool for a different job — a mat is fine for warming a whole tray of seedlings, but it can't give a single seed a precise, stable number.
How much difference does the warmth actually make?
More than most people expect. Paired with a silicone skin, growers commonly see a taproot within 24–36 hours on a suitable seed — against 7–21 days for a chilli in ambient conditions, or 5–10 for a tomato. Those conventional timelines are largely a symptom of unstable temperature: a seed sitting below its ideal range overnight isn't growing, it's waiting. Holding it in range continuously is the entire job this unit does. Results vary with species and seed freshness, and warmth alone won't revive a dead seed.
Can one Heat Pack. run two skins at once?
No. It's designed to power one skin at a time. Running germinations in parallel means adding Heat Pack. units — which is part of why it's sold separately.
Can I leave it running 24/7?
Yes. It's built for continuous operation throughout a germination cycle, and at roughly 1 W holding draw there's no reason to switch it off between checks.
Does it come with a power adapter?
No. You'll need a USB-C wall adapter rated 5 V at a minimum of 1.5 A, with 20 W or higher recommended for consistent output. Most modern phone chargers meet that.
We want this for a classroom — is the Heat Pack. what we need?
Not on its own — it's a heater with no chamber, so it won't germinate anything by itself. For teaching, either the Sprout. + Heat Pack. Kit (plugs into a phone charger, seed visible throughout) or FlexiGerm. (six pods, no power at all) is the better buy. For classroom sets or bulk quantities, get in touch.
Will it work with GermiPad?
Yes — that's the intended pairing. GermiPad ships without a heater because it's designed to run on a Heat Pack. you already own. If you're starting fresh and heading straight for GermiPad, buying this unit on its own is the right route; you don't need the Sprout. skin unless you also want single-seed germination.
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