Under the hood: how Charge Pack manages your battery
Short on time? We've got you. Here are the basics:
On a normal day, your battery will be scheduled so that you earn most from your tariff — no intervention needed
On a Session day, we may instruct your battery to to either charge or discharge to help balance the grid, and we make sure you always come out ahead financially
If you have an EV, we’ll co-ordinate both devices, with a few caveats worth knowing about
Credits are calculated using your devices’ data — see below for how the maths works
What your battery does on a normal day
The day-to-day schedule depends on which tariff you're on.
Intelligent Octopus Go or Octopus Go (with Outgoing Octopus)
These tariffs have a cheap overnight rate, so the default schedule is built around making the most of that window:
Overnight: We charge your battery to 100% during your off-peak window
During the day: Your battery runs in self-consumption mode, meaning the battery dynamically adjusts all the time to make sure your battery is powering your home directly, rather than drawing from the grid at the higher day-rate.
Grid export: We only export to the grid if our personalised forecast suggests there'll be enough charge left after covering your home's consumption for the rest of the day. In winter, with higher home loads, this is unlikely. We want your battery to be down to the minimum state of charge (often 20%) at the start of the off-peak window.
Standard Variable Tariff (+ Outgoing Octopus)
All day: Self-consumption — your battery covers your home load wherever possible
Grid export: This only happens as part of a Charge Pack session. Outside of sessions, we don't export to the grid because your import rate is higher than your export rate.
What happens on a Session day
Sessions are where Charge Pack earns its keep. We constantly monitor grid forecasts and wholesale energy markets, and when there's an opportunity — a glut of renewables, or the grid needs a boost at peak time — we run a Session.
Sessions come in a few flavours:
Power out session: We instruct your battery to discharge to the grid during a specific window, sending power back when it's most valuable.
Charge up session: We charge your battery when there's surplus renewable energy available — capturing cheap green electrons before they'd otherwise go to waste or require a wind farm to curtail.
Pre-charge: If you're heading into a Power out session and your battery might not be fully loaded, we'll top it up first to maximise your contribution.
Pre-discharge: Conversely, if a large Charge up session is coming up, we may discharge first to free up capacity.
You'll typically get a heads-up at least a few hours in advance, with the Session details in your notification email.
After the Session window closes, your battery returns to its standard day-to-day schedule.
If you also have an EV connected to us
Managing a home battery and an EV charger simultaneously adds complexity — both devices want access to your cheap overnight electricity, and their schedules can occasionally clash.
Intelligent Octopus Go and Charge Pack share the same underlying platform, which means we can see both devices and try to schedule them sensibly. In practice, though, there are moments where the two interact in ways that aren't always smooth — for example, a large EV charge can affect the power available for battery operations, or vice versa.
There's an added layer of complexity in that batteries, EVs and chargers all come from different manufacturers and communicate in slightly different ways. With so many combinations in the wild, edge cases are inevitable — behaviour that works perfectly with one setup can surface unexpected interactions with another.
We're actively working on tightening the coordination between the two. If you notice unexpected behaviour — your battery not charging as expected on a night your EV is also plugged in, for instance — it's worth flagging to us so we can take a look at the specific interaction.
How Session credits work
This is where it gets proper techy.
During a session, here's what we cover:
Battery charging at the day-rate: If your battery charges during a session that falls in your day-rate window, we credit you the difference between your day-rate and your off-peak rate. The net effect: you've effectively billed at your cheap off-peak rate, even mid-afternoon.
Battery discharging to the grid: We credit you the gap between your import day-rate and your export rate for the kWhs that you’ve exported. This covers the cost of any grid energy you pull in during or after the session window — so you always make a profit on every kWh exported.
Session bonus: On top of the above, each session includes an additional bonus payment. The bonus amount varies, depending on the market opportunity. You are informed of the exact amount in your session notification email.
The monthly minimum:
At the end of each month, we add up all your session credits and bonuses. If the total falls below £12, we top you up to hit that minimum. Join mid-month? The £12 is prorated for the exact number of days you were live.
A worked example:
You're on Intelligent Octopus Go with an 8p/kWh off-peak rate and 32p/kWh day-rate, and you're on Outgoing Octopus with a 12p/kWh export rate. You joined Charge Pack on day 16 of a 30-day month.
A session runs: your battery charges 2 kWh between 19:00–20:00 (during your day-rate window), then discharges 1.5 kWh between 20:00–21:00 to the grid. The session bonus is £1.
Your session credit breaks down as:
Charging credit: 2 kWh × (32p − 8p) = 48p
Discharging credit: 1.5 kWh × (32p − 12p) = 30p
Session bonus: £1.00
Session total: £1.78
Your prorated monthly minimum is £12 × 16/30 = £6.40. Since your session earnings (£1.78) are below that, we top you up by £4.62 — hitting your guaranteed minimum automatically.
COMING SOON: you’ll soon have all your session credits available in the app! If you have any questions, email us at hello@octopus.energy and we’ll look into the calcs for you.
The bigger picture
Charge Pack isn't just about the monthly credit. Every session where your battery absorbs surplus renewables or discharges to support the grid at peak demand is a small but real contribution to a cleaner, more stable energy system — one where we curtail fewer wind farms and fire up fewer gas peakers to fill the gaps.
Your battery is already there, already cycling. Charge Pack just makes sure it's doing it at exactly the right moment.
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Phil Steele
Future Technologies Evangelist