Octopus Free Electricity Sessions: How to Maximise Them

Octopus Energy occasionally offers free electricity sessions — short periods where your electricity is completely free. For solar and battery owners, these events are an opportunity to save significant money with the right preparation.

What Are Free Electricity Sessions?

Octopus Energy runs promotional events — usually called "Free Electricity Saturdays" or "Power Ups" — where electricity is free for a set window. These events serve multiple purposes:

• Marketing: Generates publicity and customer goodwill
• Grid balancing: Encourages consumption during periods of high renewable generation
• Customer engagement: Rewards active customers who shift their energy usage

Events typically happen a few times per year, usually on weekends, and last 1–2 hours. Octopus notifies customers via email and the app, usually a few days in advance.

How They Work

During a free electricity session:

• Your electricity import rate drops to 0p/kWh
• Everything you use during the window costs nothing
• Your smart meter records the consumption, and Octopus credits the cost
• Export rates may also be affected (usually 0p during the window — so don't export)

You don't need to do anything technical to benefit — just use electricity during the window. But with planning, you can maximise the value significantly.

Maximising Value: The Priority List

When a free session is announced, here's what to prioritise (highest value first):

1. Charge Your Battery to 100%

If you have a home battery, force-charge it from the grid during the free window. A 10kWh battery charged for free saves you £2.60 at 26p/kWh — the electricity to use tomorrow.

How: Set your inverter to force-charge mode. Via GivEnergy app, GivTCP, or Predbat override.

2. Charge Your Electric Vehicle

EV charging is the single highest-value use of free electricity. At 7.4kW charging for 2 hours, you get 14.8kWh for free — worth £3.85 and enough for roughly 50 miles of driving.

How: Plug in your EV and set charging to maximum rate before the session starts.

3. Boost Your Hot Water

Run your immersion heater to heat the cylinder to maximum temperature.

How: Override your diverter (Eddi/iBoost+) to full power, or manually switch the immersion heater on via its switch/timer.

4. Run High-Consumption Appliances

• Washing machine (hot wash if needed)
• Tumble dryer
• Dishwasher
• Oven (batch cooking)
• Iron

5. Pre-Heat or Pre-Cool Your Home

If you have a heat pump or electric heating, boost your heating during the free window. A well-insulated home retains heat for hours after the heating stops.

In summer, pre-cool your home with air conditioning if you have it.

Preparation Checklist

When Octopus announces a free session (usually 2–7 days in advance):

The day before:

• Deplete your battery to ~20% by using it normally (don't charge overnight)
• Ensure your EV is plugged in but not fully charged
• Load the washing machine/dishwasher ready to start
• Check your immersion heater switch works

On the day:

• 10 minutes before: Set battery to force-charge from grid
• 10 minutes before: Set EV to charge at maximum rate
• At session start: Turn on immersion heater, start appliances
• During session: Monitor battery SOC and adjust if it fills before the window ends
• At session end: Return battery to normal mode, stop force-charging

After the session:

• Verify the free period appears correctly on your Octopus bill
• Check battery SOC — should be near 100%
• Return all settings to normal

How Much Can You Save?

Over 4–6 free sessions per year, this adds up to £30–£50 — not life-changing but a nice bonus, especially when it costs nothing but preparation.

Automation with Home Assistant

If you use Home Assistant, you can partially automate your free session response:

Predbat

Predbat can be configured to recognise free electricity periods and automatically force-charge the battery. Check Predbat's documentation for the "free session" or "override" configuration.

Custom Automation

Create an automation triggered by a calendar event or manual switch:

• Set battery to force-charge mode
• Turn on designated smart plugs (immersion heater, EV charger)
• Send a notification to start manual appliances
• Revert all settings after the session window

Saving Allowance and Related Programmes

Beyond free electricity sessions, Octopus runs other grid-balancing programmes:

Saving Sessions (National Grid ESO)

During periods of high grid demand (typically winter evenings), Octopus pays you to reduce your consumption. With a battery, you discharge your battery instead of importing from the grid — earning payments of 100–400p/kWh for the electricity you don't import.

How to participate: Opt in via the Octopus app. When a session is announced, ensure your battery is charged and ready to discharge during the session window.

Octopus Flux Export Peak

On Octopus Flux, the 4–7pm export rate is typically 25p/kWh. While not "free electricity," planning your battery to export during this window is a daily opportunity to earn from your stored solar.

Agile Plunge Pricing

On Octopus Agile, prices occasionally go negative — you're paid to use electricity. These aren't announced events; they happen in real time based on grid conditions. Predbat handles these automatically if configured.

These products help you maximise free electricity sessions:

GivEnergy All-in-One 9.5kWh Battery

£5,500

capacity kwh

9.5

usable capacity kwh

8.6

chemistry

LFP

cycles

6000

View on Amazon

Affiliate link — we may earn a small commission at no extra cost to you

myenergi Eddi Solar Diverter

£185

max power w

3000

modes

power_divert,timed_boost

outputs

2

priority

configurable

View on Amazon

Affiliate link — we may earn a small commission at no extra cost to you

Who Benefits Most?

Free electricity sessions reward prepared households with:

• Large batteries — more storage capacity = more free electricity banked
• EVs — the highest-power single load most homes have
• Smart home automation — automated response means you don't have to remember or be home
• Immersion heaters — a simple way to store energy as hot water

Even without a battery or EV, running your washing machine, dishwasher, and oven during a free window saves real money with zero effort beyond timing.

For getting set up with Octopus smart tariffs, see our Octopus API guide. For automated battery management, see our Predbat guide.

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