For years, my answer to “which presence sensor should I buy?” came with an asterisk the size of a power brick. mmWave radar — the technology that can tell a sleeping human from an empty couch — was simply too hungry to run on batteries. If you wanted real presence detection instead of PIR motion blips, you accepted a USB cable snaking down your wall. In my house that meant exactly two rooms got proper presence detection, because those were the two rooms where I could hide the wire.
That constraint quietly died over the past year, and I don’t think enough people noticed. So today: a look at where presence sensing stands in mid-2026, what I’d actually put on my own walls, and the category of devices I’d still avoid even though they’re a third of the price.
The trick that made batteries viable
Quick recap for anyone who hasn’t fallen down this rabbit hole. PIR sensors detect changes in heat, which means they need actual movement. Sit still reading a book and your lights go out — the classic smart home embarrassment. mmWave radar detects micro-movements like breathing, so it knows you’re still there. The catch: radar transmits constantly, and constant transmission eats coin cells for breakfast.
The solution that finally shipped in current-generation hardware is almost annoyingly obvious: use both. A PIR sensor sips microamps and acts as the doorbell — the moment it sees motion, it wakes the mmWave radar, which takes over and holds presence until the room is genuinely empty. Then the radar goes back to sleep. The 60 GHz radar chip both Aqara and SwitchBot use in their latest battery sensors is built around exactly this duty-cycling idea, and it’s the reason we’re suddenly seeing multi-year battery claims on devices that would have lasted weeks before.
What I’d buy for battery-only spots
The Aqara FP300 is the one that’s been going in and out of stock since launch, and having read the teardowns and long-term reviews, I understand why. It packs the 60 GHz radar, a PIR trigger, plus light, temperature and humidity sensors into one puck running on two CR2450 cells, with a claimed battery life of up to three years. It speaks either Zigbee or Thread — you pick the firmware — and pairs with Zigbee2MQTT without any Aqara hub in sight, which is exactly how I like my devices: local, hub-free, and talking to the coordinator I already own.
One detail that matters if you’re deciding between the two radio modes: reviewers consistently report that the full set of configuration parameters is only exposed in Zigbee mode. The Thread/Matter firmware is far more limited. That tracks with my broader experience — Matter keeps promising the world and keeps shipping the lowest common denominator. For a Home Assistant household, Zigbee mode is the obvious choice, and it’s not close.
The SwitchBot Presence Sensor is the budget sibling worth knowing about: same radar chip, same PIR-wakes-radar principle, but powered by standard AAA batteries rated for up to two years. No environmental sensors, so it does one job — but AAAs are cheaper and easier to source than coin cells, and with fewer extras on board it may well outlast the FP300 in practice. If I were covering a hallway or a guest room where temperature data is irrelevant, this is where I’d save the money.
Where wires still win
Battery sensors answer “is someone in this room?” Wired sensors can answer “where exactly, and how many?” — and if you have power available, that’s still a meaningful upgrade.
The Aqara FP2 remains the zone-mapping king: up to 30 detection zones in a single room, each exposed as its own occupancy entity in Home Assistant. Desk occupied, couch occupied, dining table empty — three different automations from one device. The honest caveat: zone setup happens in the Aqara app. It’s a one-time thing and you can uninstall the app afterwards, but for a no-cloud purist it’s a compromise, and I’d rather tell you that up front than have you discover it during onboarding.
For the ESPHome crowd, Apollo Automation’s R PRO-1 is the interesting one — dual mmWave radars (an LD2412 and an LD2450) with Power-over-Ethernet, natively ESPHome so it’s fully local and endlessly tweakable. PoE on a presence sensor sounds like overkill until you remember that anyone running cameras already has a switch with spare ports. And if your budget says otherwise, the Sonoff SNZB-06P has quietly become the default cheap wired Zigbee option — nothing fancy, but it holds presence reliably.
The DIY corner
An ESP32 plus a Hi-Link LD2410B/C module is still the cheapest way into mmWave, and the ESPHome integration is mature to the point of boring — which is the highest compliment I can pay infrastructure. The newer LD2412 and LD2450 modules now have official ESPHome support too, with the LD2450 adding multi-target tracking for those who want FP2-style capability without the app. My own bare-metal Home Assistant box already runs the ESPHome add-on for other projects, so the marginal cost of one more DIY sensor is a few francs of hardware and an evening of fiddling. That evening is the fun part, if we’re honest.
What I’d still avoid
The flood of cheap Tuya-based Zigbee presence sensors on AliExpress and Amazon is still going strong, and my advice hasn’t changed: skip them. It’s not that they can’t detect presence — many do it fine. The problem is how they behave as network citizens. Several of the popular models spam the Zigbee network with constant status updates, and testers have found this essentially unfixable. A single chatty sensor can degrade a mesh that dozens of well-behaved devices depend on. Saving twenty francs on a sensor isn’t worth destabilizing the network your whole house runs on.
The bottom line
For the first time, my recommendation doesn’t depend on where your power outlets are. Battery mmWave is no longer a compromise — the FP300 in Zigbee mode is a genuinely complete presence sensor you can stick anywhere. Wires still buy you zones and multi-person tracking, and DIY still buys you the most capability per franc. The only losing move in 2026 is the bargain-bin Tuya puck that turns your Zigbee mesh into a shouting match.
Next on my list: replacing the PIR sensor in the office — the room where I sit stillest, longest, and get plunged into darkness most often. If the FP300 survives a Swiss winter of radiator-adjacent mounting, you’ll read about it here.
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