Rates checked: 19 September 2026

How Ember locks Octopus Agile windows

Read 48 prices. Pick the cheapest stretch that still hits the target. Run the Tesla home charge.

Octopus Agile publishes 48 half-hourly prices for the next day, usually nearer 4pm. The cheap stretch is not a fixed overnight block. It moves. If you charge at 18:30 on a plunge day you can pay around 50p/kWh; if you catch the floor you can be paid to charge. That is the whole argument for automation.

Ember is built for that job, for Tesla drivers on iPhone who have already chosen Agile. It is not a tariff. It does not switch you. It watches the graph so you do not have to.

What Ember actually does

  1. 01

    Reads the 48 Agile prices

    Once tomorrow’s rates land, Ember pulls the half-hourly series for your region and ranks every slot. Same market Octopus publishes; no invented prices.

  2. 02

    Picks the cheapest stretch to your target

    You set a charge target once (for example 80%). Ember finds the cheapest contiguous window that can still hit that target before you need the car, whether that stretch falls overnight, at midday, or somewhere in between.

  3. 03

    Runs the Tesla home charge

    When the window opens, Ember starts charging at home. When it closes, it stops. You plug in. That is the whole job.

Free charts vs paid automation

The app is free to download. Free charts show today’s and tomorrow’s cheapest window and the full Agile series for your region. That is enough if you like scheduling the car yourself.

Paid automation is £3.99/month or £38.99/year. That is the set-and-forget path: Ember locks the window and drives the charge. Upgrade sits inside the app. No card is required to try the free charts.

Tesla + iPhone only

Scope today

Ember supports Tesla + iPhone only. Other EVs and other phones can still use the Agile vs Intelligent Go comparison; Ember’s automation is not the path yet.

If you are on Intelligent Octopus Go, Octopus already schedules the car into a cheap window. Ember is for the Agile graph, not a replacement for Go’s smart charging.

When this is worth it

Automation earns its keep when the cheap stretch is not the classic overnight block. On the 20 September 2026 London example, the floor sat at 13:00 at -5.0p/kWh while 18:30 hit 50.2p. Ember aims for the floor, not the peak.

Early fleet figures (7 Tesla + iPhone drivers, not a promise): £393.76 saved across 223 automated charges, roughly £198 per driver per year, 10.5p/kWh captured. Details live on the comparison page.

Get Ember for Agile

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