Your history stops
disappearing.
Home Assistant purges its detailed history after ten days. Four PLCs and no historian is worse. Send yours here instead: full resolution for 14 days to 2 years by plan, and hourly min/max/average for 10 years on every plan, including the free one.
No signup needed · sample data
The cheapest managed historian we can find costs $970 a month and will not sell you fewer than 5,000 tags. Cheaper than that, "managed" means a database handed to you on a rented VM — its schema, its retention and its upgrades are still your job — or a server you rack, patch, back up and restore yourself. Here are the prices, with sources.
Whatever you already run
Every plan includes every integration and every feature. Plans differ in scale and support, not in what the product can do.
Home Assistant
Point HA's built-in InfluxDB integration at Tag Historian. Five lines of YAML, nothing to install, history that outlives the SD card.
Read the guideMQTT
A collector runs next to your broker and connects outward - no port forwarding, no broker exposed. Mosquitto, zigbee2mqtt, Tasmota.
Read the guideOPC UA
Subscribe to the PLC tags you list - secured endpoints (Basic256Sha256), typed values with exact OPC UA quality codes, and disk buffering when the uplink drops. Beta.
Read the guideInfluxDB line protocol & REST
POST /api/v2/write accepts line protocol unchanged, so Telegraf and any InfluxDB v2 client writes without modification. Plus a REST batch API and Azure IoT Hub.
Endpoint reference10 years of hourly history - on every plan
Full resolution for 14 days on Free, 6 months on Pro, 2 years on Business. After that the individual readings go and the hourly min/max/average/count for every tag stays for 10 years. Nothing is parked offline: a five-year chart comes back from the day tier in about 1 800 points.
How retention worksDeadband compression
Store a reading when it moves by more than the deadband, and at least once an hour regardless. Stored points are 22 bytes each: timestamp, typed value, the full 32-bit OPC UA status code and a per-record checksum.
Alerting with signed webhooks
Threshold rules with in-app alerts on every plan. Webhook delivery on Pro and above is signed HMAC-SHA256 over timestamp and body, so your receiver can verify it really came from us.
Query, stream, export
A REST API for history, a WebSocket subscription for values as they arrive, an official Python client for scripts and cron jobs (installed from github.com/softi-dev/tag-historian-clients — not yet on PyPI), and exports of measurements, aggregates and tag metadata as Parquet, CSV or JSON. No export fee and no proprietary step in the middle.
Hosted in Sweden
Azure Sweden Central, with a nightly backup to a geo-redundant vault in the paired Swedish region. Every file is written under your own customer id, and a request for someone else's data is refused rather than filtered.
Both RPO numbersFour Simple Steps
From sensor to insight. Hobbyists to industrial scale.
Connect
Home Assistant via its built-in InfluxDB integration, OPC UA and MQTT via a collector on your own network, Azure IoT Hub, or the REST API. Pick whichever you already run.
Ingest
Send measurements with timestamps, batched or streaming. A 2xx means the reading is committed to the write-ahead log, not merely received. If the buffer ever fills you get 503 with Retry-After - never a silent drop.
Store
Deadband compression into a compact binary format. Full resolution for 14 days to 2 years depending on plan - hourly min/max/average/count then stays for 10 years on every plan, including Free.
Use it
Charts and dashboards in the app, a REST API for your own tools, a WebSocket subscription for live values, threshold alerts, and exports to Parquet, CSV or JSON whenever you want out.
Priced by tag, not by reading
A tag is one series — one Home Assistant entity, one MQTT topic, one OPC UA node. Cost follows how many series you keep, not how often you sample them.
Every plan includes every integration and every feature — Home Assistant, MQTT, OPC UA, REST, line protocol, dashboards, alerting and exports. Plans differ in scale and support.
Free
Enough to point a real system at it and see whether any of this is worth paying for.
- 5 tags
- 50k readings/day
- 14 days at full resolution
- 10 years of hourly history
- In-app alerting
- Email support, direct to the developer
Pro
A house, a boat, a workshop, or one machine on a line.
- 50 tags
- 500k readings/day
- 6 months at full resolution
- 10 years of hourly history
- Signed webhook alerting
- Email support, direct to the developer
Business
A small plant: several machines, a boiler house, a few hundred signals.
- 500 tags
- 5M readings/day
- 2 years at full resolution
- 10 years of hourly history
- Signed webhook alerting
- Email support, direct to the developer
Enterprise
More tags than Business, a contractual SLA, or something the standard plans do not cover.
What that conversation usually covers
- Tag limits beyond 500
- A retention window that matches your reporting obligations
- What uptime we can commit to in writing, and what it costs
- Getting your data out of whatever it is in today
Not sure which of these you need — or whether you need any of them? What the alternatives cost and whether Home Assistant already does this for free.
Questions people ask before they send us anything
- How much does Tag Historian cost?
- Free is €0 for 5 tags. Pro is €9 a month for 50 tags. Business is €89 a month for 500 tags. Prices are in euro and billed monthly.
- How long is my data kept?
- Individual readings are kept at full resolution for 14 days on Free, 6 months on Pro and 2 years on Business. After that window the individual readings are deleted but the hourly minimum, maximum, average and count for every tag remain for 10 years — on every plan, including the free one.
- What is a tag?
- One tag is one series: one Home Assistant entity, one MQTT topic, one OPC UA node, or one field of one Telegraf metric. Plans are priced by tag count rather than by how many readings you send, because storage cost tracks the number of series, not the sample rate.
- How do I get data in?
- Home Assistant through its built-in influxdb integration, Telegraf through outputs.influxdb_v2, MQTT and OPC UA through a collector you run on your own network, Azure IoT Hub, or a REST batch API. Anything that speaks the InfluxDB v2 write endpoint works unchanged.
Start Free
5 tags. 50,000 readings a day. 14 days at full resolution, and 10 years of hourly history. No credit card.
Next step after signing up: pick a guide and create an API key. Each guide names the scope its key needs — the ingesting ones want Write, Grafana wants Read.