Privacy notice
Last updated 1 September 2026
This page explains exactly what halfhourly.uk stores, why, and how to get rid of it. The short version: you can browse prices without giving us anything at all, and if you do connect an account you can delete everything in one click.
We only ever read your Octopus account. Your API key lets this site read your tariff, your meter details and your consumption readings, and we use it for nothing else: we never change a tariff, switch supplier, move money, alter a direct debit or submit a meter reading. Treat the key like a password all the same — it identifies you to Octopus, so anyone holding it can act as you against their API. You can revoke it at any time from your Octopus dashboard, which instantly cuts off our access.
Who we are
halfhourly.uk is operated by Brindleford Technology, the data controller for the purposes of UK GDPR.
We are an independent tool. We are not Octopus Energy, and we are not affiliated with, endorsed by or connected to them.
Browsing without an account
Prices, the tariff comparison and the JSON API need no account and no personal data. We do not ask for your name, address, phone number or date of birth at any point — not even if you do create an account.
What we store if you create an account
Being straight with you: several of these are personal data under UK GDPR, because they relate to an identifiable person. Consumption readings in particular can reveal when your home is occupied, so we treat them carefully.
| What | Why | Personal data? |
|---|---|---|
| Email address | Signing in, and sending the alerts you switch on. | Yes |
| Password | Signing in. Stored only as a hash, never as text we could read. | Yes |
| Octopus API key | Reading your tariff and consumption. Encrypted at rest. | Yes — it can read your name and address from Octopus |
| MPAN and meter serial | Identifying which meter's readings to fetch. | Yes — an MPAN identifies a specific property |
| Half-hourly consumption | Working out what you actually spent. | Yes — it can indicate when you are home |
| Your region and tariff | Showing the right prices. | Only in combination with the above |
We do not store your name, postal address, phone number, bank or card details, or your Octopus password. We never ask for your Octopus password and you should never give it to us or to anyone else.
Tariff prices are not personal data
The historic price data this site keeps — unit rates and standing charges per region — is published tariff information. It is identical for everyone in a region and is not linked to any individual.
Lawful basis
- Contract. Storing your credentials and consumption so we can show you the dashboard you asked for.
- Consent. Sending alerts. You choose which, and you can turn them off at any time.
- Legitimate interests. Keeping the service running, secure and free of abuse.
Background imports
Once you connect an account, we fetch your half-hourly readings from Octopus on a schedule — roughly hourly — whether or not you are signed in. That is the point of the service: your history is ready when you look, rather than assembled while you wait. Imports stop the moment you disconnect, delete your account, or revoke the key at Octopus.
How long we keep it
- Consumption readings: for as long as your account is active, so your history stays useful.
- Everything else: until you delete your account.
- After deletion: removed from the live database immediately, and from encrypted backups within 30 days.
If you stop using the site
We do not keep your data on the off-chance forever. If you do not sign in for 12 months, an automatic job deletes your stored API key, your meter details and your imported readings. About a month beforehand we email you a warning, and signing in once cancels it. Your sign-in itself survives, so if you come back later the site can tell you what happened and offer to reconnect — your history then re-imports from Octopus, because the source of truth was always theirs, not ours.
Deleting your data
One button in your account settings deletes your credentials, meter details and consumption history. There is no retention period and no email exchange to go through. You can also revoke the API key on your Octopus dashboard, which stops our access immediately whether or not you delete the account.
Who we share it with
Nobody. We do not sell data, we do not share it with advertisers, and we do not use it to build profiles for anyone else. The only third parties involved are:
- Octopus Energy — we read from their API on your behalf.
- Our hosting provider — the servers this site runs on, in the UK.
Our analytics run on our own server in the UK, set no cookies, and do not track you across other sites.
Cookies and local storage
No tracking or advertising cookies, and therefore no consent banner. We use two things, both strictly for the preferences you set yourself:
hh_region— a cookie remembering the region you picked, so prices are right next visit. Expires after a year.hh_theme— browser local storage remembering light or dark. Never sent to the server.
Signing in will also set a session cookie, which is required for the account to work.
Security
- Everything is served over HTTPS.
- Passwords are hashed, never stored as readable text.
- API keys are encrypted at rest, so a stolen database dump does not hand over your keys.
- The database is not reachable from the public internet.
No system is perfectly secure. If anything happens that puts your data at risk, we will tell you and the ICO as the law requires.
Your rights
Under UK GDPR you can ask for a copy of your data, correct it, delete it, restrict or object to how we use it, and take it elsewhere. Ask us and we will respond within one month, free of charge. If you are unhappy with our answer you can complain to the Information Commissioner's Office.
Changes
If we change what we collect or why, we will update this page and, for anything significant, tell account holders by email before it takes effect.