Node-RED vs Home Assistant Automations — When to Use Which

One of the most common questions from intermediate HA users is: when do I use Node-RED instead of HA's built-in automations? The short answer is that HA automations are excellent for 80% of use cases, and Node-RED is invaluable for the other 20% — but it's important to know which is which before you start building.

What HA Automations Do Well

• Simple trigger → condition → action flows
• Time-based scheduling (turn on at 07:00)
• State change reactions (door opened → light on)
• Notification sending
• Scene activation
• Entity state changes with conditions

For a home with 10–20 automations doing sensible things like "turn off lights when no motion" or "arm alarm when everyone leaves" — HA automations are perfect. The UI editor is good, the YAML is readable, and there's no extra addon to manage.

Where Node-RED Wins

1. CSV File Logging

HA has no native file-writing capability. If you want to log sensor data to CSV for later analysis — solar production, biltong box humidity, energy consumption by circuit — you need Node-RED. The fs node in Node-RED handles file reads and writes cleanly.

A real example: a 78-column solar diagnostic logger running on a SolaX X1-Hybrid system captures PV power per string, battery SOC, charge rate, grid power, inverter mode, outdoor temperature, and a dozen calculated values — every 60 seconds — to two files (master permanent log + session buffer for API calls).

2. External API Calls with Logic

Making an API call in HA automation is possible but awkward. In Node-RED, the HTTP request node handles it cleanly, and you can wire the response directly into decision logic. A production flow uses the Claude API to evaluate current solar conditions and recommend an AC mode — the API response feeds directly into climate service calls with fallback logic if the API is unavailable.

3. Complex Multi-Step Sequences with Delays

Sequential irrigation is a good example. Zone 1 runs for 12 minutes, then Zone 2 for 15 minutes, then Zone 3 for 8 minutes. In HA automations, this requires a script with nested delays and is hard to modify. In Node-RED, it's a linear flow with delay nodes between zone on/off service calls — visually obvious, trivially editable.

4. Stateful Flows with Running Counters

Node-RED has persistent flow context (flow.set/flow.get) that survives between messages. This is ideal for drying phase detection: tracking peak absolute humidity delta, elapsed hours, batch ID, and phase transitions across dozens of sensor readings per hour.

5. Error Handling and Retry Logic

HA automations fail silently when a service call errors. Node-RED lets you wire catch nodes that detect failures and implement retry logic, send notifications, or fall back to a safe state. For API-dependent automations (like the Claude AC controller), this is critical.

Setting Up Node-RED in HA

1. Install from addon store: Settings → Add-ons → Node-RED (Community)
2. Configure credentials: Set a username and password in the addon configuration before first start
3. Install HA nodes: In Node-RED → Manage palette → search "node-red-contrib-home-assistant-websocket" — this gives you native HA entity nodes
4. Connect to HA: Drag a "server config" node, set URL to http://supervisor/core, token to a Long-Lived Access Token from your HA profile

The fs Module — File Writing in Node-RED

By default, Node-RED sandboxes function nodes and blocks require(). To enable file system access:

1. Create a new flow tab called "Setup"
2. Add a single inject node (fires once on deploy) → function node
3. In the function node: global.set('fs', require('fs'));
4. In any other function node: const fs = global.get('fs');

Files written to /homeassistant/www/ are accessible via HA's media browser at http://your-ha-ip:8123/local/filename.csv

Real Flow: Biltong Box Monitor

This flow runs every 5 minutes during an active batch. It reads inside and outside humidity and temperature sensors, calculates the absolute humidity delta (the key drying metric), determines the current drying phase, and appends a row to a batch-specific CSV file. When the delta starts declining significantly, it sends a push notification that the batch is entering the "Near Done" phase.

The absolute humidity calculation (converting relative humidity + temperature to grams of water per cubic metre of air) is essential — relative humidity alone is meaningless without temperature, since warm air can hold much more moisture than cool air. A 70% RH reading at 30°C represents far more water vapour than 70% at 15°C.