> ## Content Index > Fetch the complete content index at: https://www.goodkit.io/llms.txt > Use this file to discover other available public pages before exploring further. # Shelly on a Boat: Cheap Smart Automation for 12V Marine Systems - URL: https://www.goodkit.io/shelly-on-a-boat-cheap-smart-automation-for-12v-marine-systems/ - Published: 2026-04-08T14:15:35.000Z - Updated: 2026-09-06T01:59:10.000Z - Description: Shelly smart relays cost and run on DC. We use them to automate lights, fans, and monitoring on our sailboat with Home Assistant. - Author: goodkit crew - Tags: Marine, RV, AI, Reviews, #approved At a glance Choose the exact model—not just “a Shelly.” The full-size 1 Gen4 and the AC-powered Mini are different products. Check stabilized power, DC contact ratings and environmental protection before buying. [Shelly 1 Gen4 · manufacturer](https://us.shelly.com/products/shelly-1-gen4?ref=goodkit.io) ## Why Shelly on a Boat? Shelly makes compact smart relays and sensors that can work locally with Home Assistant. Some models can be useful aboard, but their power supplies and switching ratings differ. A DC-capable relay contact does not mean the device itself can be powered by a boat battery. We run multiple Shelly devices aboard our sailboat. They control lights, monitor temperatures, and automate systems that used to require manual switches or expensive marine-specific controllers. ## The Key Models for Marine Use ### Choose a DC-powered model—not the Mini The full-size Shelly 1 Gen4 accepts stabilized 12V DC or 24–48V DC power. Its DC switching limit is 10A at up to 30V. Those are different ratings: a 48V supply rating does not make it suitable for switching a 48V load. Potential uses for a correctly selected, installed and protected relay include cabin lighting and non-critical controls. Our experience is with Shelly automation aboard; it is not a claim that we tested every current model. - Control cabin lighting from a dashboard - Retain local physical operation with the correct switch configuration - Monitor activity without depending on a cloud service Keep independent manual control for safety-critical equipment. A physical switch input is not a bypass around failed relay hardware. ### Shelly H&T Gen3 Temperature and humidity sensor with an e-ink display. Battery powered, reports over Wi-Fi. We have these in the engine room, the lazarette, and the main cabin. The engine room sensor triggers a Home Assistant alert if temperature exceeds a threshold — critical for catching overheating before it becomes an emergency. ### Shelly Plus Plug S For plug-in shore-power monitoring, choose a smart plug rated for your country’s voltage, socket and load. Do not assume a European Plug S suits a US outlet, or that a plug-in relay can safely handle a water heater, air conditioner or charger. ## The 12V DC Question Correction: Shelly 1 Mini Gen3 and Gen4 are AC-powered devices, not native 12V relays. The full-size Shelly 1 Gen4 is a different product. Its 12V input requires stabilized power; a nominal 12V boat circuit changes voltage while charging. Check the exact [Shelly 1 Gen4 manual](https://us.shelly.com/blogs/documentation/shelly-1-gen4?ref=goodkit.io) for power, terminals, contact ratings and installation conditions. Use appropriate supply regulation, circuit protection and enclosure; do not copy a wiring diagram from another Shelly generation. ## Connecting to Home Assistant Shelly devices connect to Home Assistant via the native Shelly integration — no MQTT configuration needed. Once they are on your boat's Wi-Fi network, Home Assistant auto-discovers them. From there, you can: - Build dashboards showing all your boat systems in one place - Create automations (lights on at sunset, fans on above 80°F, bilge pump alerts) - Log historical data — temperature trends, power consumption, switch activity - Set up notifications via phone, email, or Telegram when something goes wrong We run Home Assistant on a Raspberry Pi 4 with a Zigbee coordinator for additional sensors. The Pi draws about 3W — negligible on a boat power budget. ## Reliability at Sea The biggest concern with smart home devices on a boat is reliability. If your Wi-Fi router reboots, will your lights stop working? A properly configured physical switch can still command a powered relay without Wi-Fi. That does not protect against loss of power or a failed relay. We have had good service from our Shelly devices aboard, but they are not a substitute for independent controls on essential equipment. ## What It Costs Price the complete installation: relay, any required stabilized power supply, protection and enclosure. Comparing the bare price of an AC Mini relay with a marine controller is not a like-for-like comparison. ## The Bottom Line Shelly plus Home Assistant can be useful and economical aboard when the exact hardware fits the circuit. Start with a non-critical application, verify the ratings and retain local control. Buy for compatibility first, not the smallest case or lowest price. ## Related Articles - [Home Assistant + Shelly on 12V DC](https://www.goodkit.io/home-assistant-shelly-on-12v-dc-smart-automation-for-rvs-and-boats/) - [Best Marine Battery Monitor: Victron SmartShunt 500A](https://www.goodkit.io/best-marine-battery-monitor-victron-smartshunt-500a-review/) - [AI Tools for Marine Navigation](https://www.goodkit.io/ai-tools-for-marine-navigation-and-boat-monitoring/) The Shellys are the muscle; Home Assistant is the brain. If you haven't set that up yet, our [Home Assistant setup guide for boats and RVs](https://www.goodkit.io/home-assistant-boat-rv-setup-guide/) takes you from blank SD card to your first useful automation. ## Choose compatible hardware - [Shelly 1 Gen4 — full-size model and specifications](https://us.shelly.com/products/shelly-1-gen4?ref=goodkit.io) - [Home Assistant Green — hardware and retailers](https://www.home-assistant.io/green/?ref=goodkit.io) Confirm the power supply and load ratings before ordering. These are current hardware options, not a claim that every model was tested aboard. The verdict Useful—with the right model. value10 / 10 versatility9 / 10 ease8 / 10