It was about 4pm on Saturday 15th February 2020 a post of my Facebook feed showed a picture of negative energy pricing for later that night. Essentially people on an energy tariff called Agile from Octopus were going to be PAID to use electricity overnight.
Our family has been on the Octopus Go tariff since we installed more solar panels and battery storage in spring 2019.
With the Octopus Go tariff you pay 14.9p per kWh for 20 hours a day and then between 00:30 and 04:30 that drops to 5p per kWh. So every night both electric cars are charged, the Tesla Powerwall 2 battery charges and the Mixergy Hot Water tank heats to 100%.
However with Octopus Agile tariff the cost of electricity varies throughout the day in half hour segments. It can be as cheap as 1p per kWh overnight but at peak times this can leap top over 25p per kWh. So to maximise Agile you need to be able to vary when you use electricity, either use smart devices or set appliances to come on when the cost is cheap. Having battery storage allows us to store energy when it is cheap and avoid having to pay when the cost per kWh is high.
Storm Dennis. How can energy prices go negative? I mean, electricity still has to be made and transmitted, nothing in life is for free! Well I have seen this happen 3 times in recent weeks. You can’t turn off wind turbines! There have been some significant storms hitting the UK in recent weeks, and when the wind is blowing at gale force, but it is the middle of the night, well there is too much electricity in the grid. You can’t turn off wind turbines, or indeed Nuclear Power within a few minutes, so far better to incentivise consumers and industry to use the spare energy but paying them to use the spare energy.
Want to join Octopus Energy? Use this link and we both get a £50 credit ! https://share.octopus.energy/lush-robin-363
So that Saturday night I contacted Octopus via twitter and a couple of emails later I was switched from Octopus Go to Octopus Agile and ready to be paid to use electricity for the first time in my life. Overnight the cars charged, the hot water heated, the underfloor warmed, washing machine spun, dishwasher cleaned. By 6am the house had 63.5 kWh of energy, about what the average UK house used in 6 days. Initial cost analysis below:
Monday Update: Data from the Octowatch app lists that for the entire 24 hours on Sunday 16th as usage: 94.9 kWh – total cost : £0.86. Amazing !
So today, the 16th February we will actually be in energy credit. The Mini PHEV can drive 20 miles, the Tesla Model S can drive 220 miles, the Mixergy 250L tank will deliver 5 showers, and the Tesla Powerwall 2 will run the house all day, and we were paid to do all that. Mad, mad times. Hopefully all houses will be able to do this within a few years with smart devices switching on when prices drop, helping the National Grid maintain a constant load, and hence more efficient.
Now of course all that infrastructure in the house is not free, the cars, battery storage and hot water cylinder all have a large upfront cost. However, when I wrote the original business case for those investments I had not even factored in negative energy pricing, as that comes more common, the return on this those investments increases. Oh and nice aside, should the lights go out in Storm Dennis, the house can run on battery power for a couple of days.
Want to join Octopus Energy? Use this link and we both get a £50 credit ! https://share.octopus.energy/lush-robin-363
A quick equipment list
- Tesla PowerWall2 with Backup Gateway 2
- Mixergy 250L Hot Water Tank
- 2017 Tesla Model S 75D
- 2019 Mini Countryman SE Cooper PHEV
- Also installed: 7.3kWp Solar Array – 26 panels