Calculator

What does your smart meter data say?

Drop in your half-hourly download and see your real day: when you use electricity, how much is always on, how you compare with a typical home, and whether an EV tariff would suit you.

Verified: 23 October 2026 from your own meter data, compared with Faraday and the Ofgem price cap
How is this calculated?
Your file stays on this device. Your browser reads it and does the sums here. It is never uploaded, and nothing is saved when you close the page. You could switch off your internet connection and this would still work.

Drop your usage file here

A CSV of half-hourly, hourly or daily electricity readings

Where do I get my file?

If you have a smart meter, your supplier holds your half-hourly readings and most let you download them as a CSV from their app or online account, usually from the page that shows your usage.

OVO: in the app, go to Usage, choose View as table, then Download data. Octopus: look for the download option alongside your usage in your online account.

Download electricity, not gas, and choose half-hourly if you’re offered a choice. A full year gives the best answer; a few weeks still works. For gas, use the gas usage analyser.

Independent calculator. We don’t pass your details to installers. We don’t earn commission from the result. We update underlying rates monthly and source everything from authoritative public data. See the full methodology.

Common questions

Is my smart meter file uploaded anywhere?
No. Your browser reads the file and does every calculation on your own device. Nothing is sent to us or anyone else, nothing is stored, and the page works with your internet connection switched off once it has loaded.
How do I download my smart meter data?
Most suppliers let you download half-hourly electricity readings as a CSV from their app or online account, usually from the page that shows your usage. In the OVO app it is under Usage, View as table, Download data. Choose electricity, half-hourly if offered, and as long a period as you can, ideally a year.
What does always-on use mean?
It is the electricity your home uses even at its quietest: fridges, routers, standby lights, central heating pumps. We take the lowest reading of each day and use the typical value across all your days. Across UK homes without a heat pump, EV or solar, the quietest hour of the night averages about 216 watts.
Would an EV tariff save me money?
It depends on how much of your electricity you already use overnight. EV tariffs charge around 7.6p a kWh at night but around 36.7p in the day, for the whole home. Upload your data and we will show the share you use in the cheap window, what the switch would cost or save, and the share you would need to reach to break even.

New to smart meters? Read are smart meters worth it? and are smart meters accurate?