8.1. Octopus Free Sessions

Octopus has this year (2024) launched “Free Electricity Sessions”, When the wind is blowing or the sun is shining, rather than shutting down the turbines they are offering free energy to their customers.

8.1.1. How Does This Work?

It’s very simple, you sign up just once.

https://octopus.typeform.com/to/xUHlI2xy#kid=site

Fill in the form and done. You’ll receive an e-mail the day prior to an event notifying you of the time.

You can also look on Octopus website https://octopus.energy/free-electricity/

During the session which so far seems to be between 1300 and 1400, you get to use as much power as possible. Octopus will then look at what you normally use during this time, subtract that and that’s how much you get for free.

Octopus will then credit your account the cost of the extra power in a few weeks after the event.

8.1.2. How much can I use?

First we need to work out how much electrity I can pull from the grid during a 1 hour time slot.

I like many houses in the UK have single phase with a 100Amp Fuse. The Grid is sending 240volts

As this is for one hour 24kW = 24kWh

The maximum I can pull from the grid for the hour would be 24kWh. For safty I wont go that high, I’ve set the limiters on my system to be around 22kW so I have head room and will not blow the grid fuse which would be a real pain to get replaced.

I’m on Intelligent Octopus Go, my peak price is 23.71p and the low rate is 7p

As I’m using power during the peak time, Octopus will pay back the peak rate pricing so the maximum I would be paid is around £ 5.22. As I have solar and batteries I wouldn’t normally use the grid at this time and using this amount of power would cost me £ 1.54 if I pulled it at off peak time.

But either way it’s free power.

8.1.3. How can I pull that much?

I have two powerwall batteries each can pull 5kW, and two Myenergi Zappi Car chargers which can pull 7kW

So I can in theory pull 24kW, however I’ve set the limiters to only 22kW.

In order to do this I need to make sure there’s space in the poweralls and I have two cars plugged in with space. For the cars I only normally charge to 80% so I always have space. I can then during this time set the cars to 100%.

8.1.4. Automation

I’m running Home Assistant to monitor and manage my house. On a normal day, one Zappi is controlled by Octopus for IOG, the other is set with a schedule to charge between 2330 - 0530. The powerwalls likewise.

Prior to the Free session I need to export my powerwalls at least 10kw of power to make space, I do this via the Powerwalls schedule, set to let the powerwall know between 1100 and 1300 is a good time to export paying out at 15p. I then set the powerwall to “export Everything”, normally I have it set to just solar.

I can send 10kW back to the grid early. I can then refill the battery during the free session, and send that back again later. So in fact Octopus will pay be an additional £ 1.50 for the extra exporting.

To achieve all this I created a local calendar called “Free energy Sessions”, I then create events in this calendar when a free session is scheduled.

The first automation looks in the calendar for an event, and then 1hour 30 minutes before the event starts, tell the Powerwall it’s ok to export it’s battery.

When the event starts

• turn off the Octopus smart charging, the other option would be to set a “Boost”.

• Change Zappi charge mode to “FAST”

• Change charge target for the ID.3 and ID.4 to 100% (Checking that the car is home, and plugged in).

Finally when the session ends we need to return all the settings back to what they were. In fact I turn things back 5 minutes before the end, that way everything has shutdown and stopped pulling before the session is truely finished so I don’t risk pulling peak. This is necessary as the Zappis gradually back off rather than hard stop, and the control of the Powerwalls is via cloud which can take a minute or two to sync up when changes are made.

• re-enable Octopus Smart Charging

• Change Zappi charge mode to “Echo+”

• Set cars charge targets back to 80%.

8.1.5. How did I do?

Octopus have now run 6 sessions, so far 5 of which they have paid me £ 22.64.

Not bad, I’m averaging just under 20kW of free power, 10kw is going to my cars (5kw to each car), and 10kw back to the powerwalls ready to be exported back to the grid in the evening.

For the 6 sessions

So I will have made around £ 9 additional for holding and later export this free session power as well as gaining some extra miles on my cars.

For the IDs during summer time we’re getting around 3.5 Miles per kWh

An additional 17.5 miles of driving in each car.