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Sentinel Stick. Plug, scan, done.

A pre-flashed Pi Zero W in a small case. Plug it into a USB charger and your home Wi-Fi, scan a QR code, and you've got always-on Sentinel monitoring for £25. Bundled at cost — we don't make money on the hardware.

Skip the SD-card-flashing dance. Skip the "which Pi do I buy" decision. Skip the install guide. The Stick exists for customers who want the £1/mo Trend tier without becoming a part-time sysadmin.

Why bother with a stick?

The free Sentinel app on your phone is great. But your phone leaves the house.

The Sentinel Live tier works beautifully on your phone — open it at home, see your system, change settings. But when you leave for work or the school run, monitoring pauses. And history requires something running 24/7.

Phone app (Live, free)

  • Real-time monitoring when you’re at home
  • Settings changes when you’re at home
  • Pairing a 6-char code with an engineer

No history. No overnight fault catching. No alerts when you’re away.

Sentinel Stick (£25 one-off)

  • 24/7 monitoring, even at 3am
  • Fault alerts by email while you’re out
  • 12 months of history (with the £1/mo Trend tier)
  • Cell-level battery diagnostics (with £2/mo Engineer tier)

Needs a Trend or Engineer subscription to record the data the Stick collects. The hardware on its own isn’t useful — it’s the “always-on host” for the paid features.

Three steps

Out of the box to fully connected in under two minutes.

  1. Plug in. USB power on one side (any 5V phone charger), it’s on. Status LED blinks twice while it joins your Wi-Fi using the credentials baked into the SD image during a one-time setup on first boot.
  2. Scan the QR code on the back. Opens sentinelapp.solar pre-loaded with your Stick’s unique pairing token. Choose Live (free), Trend (£1/mo), or Engineer (£2/mo).
  3. Walk away. Stick discovers your inverter on the LAN, starts the Modbus connection, begins streaming. From this point on it just sits there, drawing about 1.5 W of power (12 kWh a year — about £4 of electricity).
Common questions

Honest answers about the Stick.

Why £25 — Pi Zero Ws are like a fiver?

The bare Pi Zero W board is ~£12. Add a case, an SD card big enough to hold the OS + agent, a power supply that doesn’t under-volt the Pi (a real failure mode in cheap chargers), shipping, packaging, our time to flash and test each unit, and Amazon’s FBA fees — £25 is roughly break-even. We’d rather price it honestly than mark it up.

Can I just buy my own Pi and skip the Stick?

Yes — that’s the existing install path on install. Flash our SD image to your own Pi or PC. The Stick exists because not everyone wants to think about hardware.

What about a Pi 4 / Pi 5 — is the Zero W enough?

For Sentinel, easily. The agent uses about 30 MB of RAM and almost no CPU. The Zero W is plenty. We picked it because it’s the cheapest Pi that meets the spec, runs cool enough not to need a fan, and uses tiny amounts of power.

What if the Stick breaks?

12-month replacement warranty included. We’ll send a new one and a freepost return label for the broken one. Beyond that, the Stick is just a Pi — any electronics shop can sort it.

Will my data still be private?

Same as the rest of Sentinel — local-first, your inverter data goes to our UK cloud only if you’ve subscribed to Trend (history) or Engineer (cell data). On the free Live tier the Stick monitors but doesn’t persist. See privacy policy.

Want one?

Join the Sentinel Stick waiting list.

We'll email you the moment the first batch is live on Amazon. No card details, no commitment — just a single email when stock is ready.

  • No card on file
  • One email when we ship — that's it
  • Unsubscribe in one click