Home Assistant for boats, end to end.

Why Home Assistant makes sense on a boat

Commercial boat-monitoring systems solve one problem at a time. A Siren 3 Pro watches your bilge and GPS. An ArmIt sensor alerts you if water appears under the galley. A Nautic Alert covers offshore comms. Each is $400–800, each runs on its own app, each charges a monthly subscription, and none of them talk to each other.

Home Assistant is the opposite pattern. One Raspberry Pi on your boat becomes a hub that reads dozens of different sensors — water, temperature, humidity, shore power, refrigerator state, cabin door — and exposes everything through one dashboard and one automation engine. No subscriptions. No cloud. No vendor lock-in. If you want a new sensor, plug it in. If you want a new automation, write three lines of YAML.

The setup isn't for everyone. If you want a device that you charge once, stick under the engine hatch, and never think about again, buy a Siren 3 — our cellular monitoring guide exists for exactly that person. Home Assistant is for the boater who's willing to invest a weekend in a system they control and can extend forever. In exchange you get capabilities no commercial platform matches.

The parts list

All prices verified against Amazon at time of writing. Every Amazon link routes through our affiliate redirect — we earn a small commission if you purchase, at no extra cost to you.

That gets you a running HA install with 9 wireless sensors and a shore-power monitor. Everything below is optional — stuff you can add if you want more depth.

The featured parts, in detail

Most parts in the list above are commodity items (an SD card is an SD card). But five components shape the build, and each deserves a closer look — especially since picking the wrong one can either cripple the setup or lock you into a proprietary ecosystem you'll regret.

How the pieces fit together

    RASPBERRY PI 5 (below deck, tucked away)
    ┌──────────────────────────────────┐
    │                                  │
    │   ┌──────────────────────────┐   │
    │   │  Home Assistant OS       │   │
    │   │  ├─ ZHA integration      │   │
    │   │  ├─ Shelly integration   │   │
    │   │  ├─ Signal K integration │   │
    │   │  └─ Automations (YAML)   │   │
    │   └──────────────────────────┘   │
    │                                  │
    └──────┬──────┬───────┬────────────┘
           │      │       │
           │      │       │ Wi-Fi (boat network)
           │      │       │
       USB │      │       └──── Shelly shore power plug
           │      │
           │      └──── Signal K server
           │              (on same Pi, or on separate chartplotter Pi)
           │
           ▼
    ┌──────────────────┐
    │ Sonoff Zigbee    │  - builds its own mesh -
    │ 3.0 USB Dongle   │
    └────┬─────────────┘
         │ Zigbee 2.4GHz
         │
     ┌───┴─────────────────────────────────┐
     ▼                 ▼                   ▼
  Water leak    Temp / humidity    Door / window
  (bilge x3)     (cabin, engine,      (companionway,
                  fridge, x3)          hatches, x3)

The important insight: the Raspberry Pi is the brain of everything. It runs Home Assistant, which owns the sensors, the automations, and the dashboard. The sensors talk to it via Zigbee (a mesh network, each sensor relays for its neighbors). The shore power plug talks to it via Wi-Fi. If you've built the open-source chartplotter from our other guide, that Pi already runs Signal K — and Home Assistant pulls data in from Signal K so your boat's real-time NMEA data (speed, position, wind, depth, engine) becomes available alongside the household-style sensors.

Why Zigbee sensors, not Wi-Fi

You'll see lots of Wi-Fi smart sensors on Amazon — Govee, YoLink, TP-Link. They're cheap and they "just work." For a house, they're fine. For a boat, there's a strong case against them:

• Battery life. Wi-Fi sensors burn through batteries in weeks. Zigbee sensors last 2–3 years on a coin cell. On a boat where you can't always change batteries easily, this matters.
• Network pollution. Each Wi-Fi sensor takes a slot on your boat's Wi-Fi. If you have 10 sensors plus your phone, tablet, laptop, and Starlink, you'll hit router limits on cheap marine routers (see our marine internet stack guide).
• Dependence on Wi-Fi uptime. If your marina Wi-Fi or boat AP reboots, Wi-Fi sensors drop off until they reconnect. Zigbee is independent — the Pi IS the network controller.
• Cloud round-trips. Many Wi-Fi sensors phone home to a vendor cloud before HA can see them. Useless when the boat is in a cellular dead zone.
• Mesh robustness. Zigbee sensors automatically relay for each other. A sensor at the bow can reach the Pi at the nav station by hopping through sensors in the saloon. Wi-Fi has no equivalent.

The tradeoff: you need a Zigbee coordinator (the $30 Sonoff dongle). Once you have it, every new Zigbee sensor is cheaper, better, and more reliable than its Wi-Fi equivalent. This decision compounds quickly as you add sensors.

Installing Home Assistant on a Raspberry Pi

Home Assistant offers a full OS image for Raspberry Pi that handles everything — no need to install Linux first and then HA on top. This is by far the easiest path.

Setting up Zigbee with ZHA

ZHA (Zigbee Home Automation) is Home Assistant's built-in Zigbee integration. It's the simplest way to use Zigbee, requires no separate software, and works natively with the Sonoff coordinator.

Adding your first sensors

Where to actually put them. Based on what failure modes a boat actually has:

• Water leak sensor #1 — bilge. Taped to the side of the bilge, above the normal water line but below where water would pool if the pump failed. This is the most important single sensor you'll install.
• Water leak sensor #2 — under galley sink. Behind the plumbing. Catches slow leaks from the P-trap or water filter lines, which otherwise ruin a cabinet before you notice.
• Water leak sensor #3 — under head floor. Holding tank seeps, macerator hose failures, toilet seal leaks. Worst smell on a boat starts here.
• Temp/humidity #1 — cabin saloon. Watches interior conditions when you're off the boat. Spike in temp + humidity is often a sign of a leak or AC failure.
• Temp/humidity #2 — engine bay. Normal is ambient. Unusual high temperatures suggest a running engine (you're away, no one should be running it) or an overheating battery.
• Temp/humidity #3 — refrigerator interior. Fridge failure is common on boats. If the fridge climbs above 45°F when you're not aboard, your food's gone. This sensor catches it immediately.
• Door/window #1 — companionway. Primary security alert. If someone opens it when you're not aboard, you get notified.
• Door/window #2 — engine hatch. Mechanical access. Unusual opens mean someone's tampering, or a fisherman's boarding to "borrow a part."
• Door/window #3 — cockpit locker (or head door). Depends on boat. Anything you want to know has been opened.

The shore-power monitor

The Shelly Plus Plug US is the single most useful $20 you'll spend on this build. Here's why:

Your boat is plugged into the dock. You're at home 50 miles away. The marina has a power outage, or your breaker trips. Your batteries start discharging. Your refrigerator compressor runs until they die. Your bilge pump won't start when needed. You have no idea any of this is happening until you come down for the weekend and everything's dead.

The Shelly is an in-wall-style plug that goes between your shore-power inlet extension and whatever you have plugged in next. It measures real-time current draw. Home Assistant reads this. If the current drops to zero — shore power lost — HA sends you a push notification. If it stays at zero for more than 5 minutes, you know it's not just a brief blip.

Pulling boat data in from Signal K

If you've already built the open-source chartplotter with Signal K, you have a goldmine of boat data — GPS, speed, wind, depth, battery voltage, engine data, AIS targets — already streaming into a Signal K server. Home Assistant can read all of it.

Add the Signal K HA integration via HACS (Home Assistant Community Store). This gives you automations like:

• Geofencing — "when the boat's GPS moves more than 100m from its mooring, alert me"
• Battery trend logging — three months of voltage history, visible as a Grafana graph
• Engine run hours — tracked as a persistent counter
• Wind alerts at anchor — "when apparent wind exceeds 25 knots while anchored, alert me"
• AIS proximity — "when any AIS target gets within 0.25nm, play an alarm"

This is where Home Assistant genuinely outshines every commercial boat monitor. A Siren 3 will tell you the current battery voltage. Home Assistant will graph it over 6 months and show you a slow decline that means your bank is aging.

Automations that actually matter

The automation engine is the whole point of Home Assistant. Here are six automations that have real-world value on a boat — every one of these has been built and tested by actual boat owners:

Building a useful dashboard

HA dashboards are flexible. Start simple: one dashboard, 4 cards arranged vertically on your phone.

Card 1 — status at a glance: big green/red indicator showing "ALL CLEAR" or listing any triggered sensors. One quick look tells you if you need to worry.

Card 2 — environmental: cabin temp/humidity, engine bay temp, fridge temp, current ambient conditions. Numbers with trend arrows.

Card 3 — power: shore power state (on/off), current draw in watts, battery voltage (from Signal K), percentage of bank capacity. The core "how's my boat powered" view.

Card 4 — access: three door sensors showing open/closed state. If anything's unexpectedly open, it's red.

Once you have this base, add things as you need them. Graphs for long-term trends. Maps with GPS (if Signal K is wired up). Weather forecasts. The temptation is to build a complex Wirecutter-style dashboard with 40 tiles. Resist it. The best HA dashboards tell you what's wrong in under 2 seconds.

Remote alerts when you're off the boat

HA can send push notifications two ways:

Via the Home Assistant Companion app (iOS and Android, free). Install it on your phone, point it at your HA instance's URL, log in. Any automation that uses notify.mobile_app_yourname hits your phone as a push notification. Works when the boat has internet access. Requires you to expose HA to the internet via Nabu Casa Cloud ($6.50/month) or a self-hosted VPN (free, but more setup).

Via SMS through Twilio ($20 to set up a phone number, then ~$0.01/message). More reliable — SMS gets through when data doesn't, and doesn't require a specific app. The Twilio HA integration is one-click; you just need an account.

For cruising boats where you might be in cellular dead zones, you need either a Starlink or a marine cellular router to give the Pi any internet at all. If you have no onboard internet, HA still logs everything locally — you just won't get alerts until you're back in range.

The honest limitations

Things this build genuinely doesn't do well, compared to commercial alternatives:

It depends on the Pi running

A Pi on a boat is more failure-prone than you'd think. SD card corruption, condensation on connectors, brownouts during engine start. If the Pi crashes, your entire monitoring stack goes dark. A commercial system like Siren 3 has engineered redundancy you don't get from a DIY build.

Battery backup needs planning

If shore power fails AND your boat batteries die, the Pi stops alerting you about the shore power failure. The optional UPS hat partially solves this (the Pi gets its own backup), but the sensors that were relaying mesh traffic lose power too. For sizing a small house bank that keeps the Pi alive between charge cycles, see our solar power for smart boats guide.

Marine environment is harsh on consumer electronics

Zigbee sensors designed for a living room don't love salt air. Aqara sensors in a dry cabin usually last years. In an engine room with fuel fumes and heat cycling, 12 months might be optimistic. Plan for replacement as part of the maintenance cycle.

First-time setup is genuinely 4–6 hours

The parts list is straightforward, but wrangling everything through first-pair can be painful. Allow a full afternoon for the base install, another weekend for automations and dashboard refinement. This isn't "plug it in and walk away."