How To Make The Most From The Octopus Flux Tariff

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As part of my smart home solar installation project, I am always looking at technology and techniques that can be used to improve our Return On Investment (ROI). Currently we are on schedule to achieve pay back in under five years but, better tariffs like the Octopus Flux tariff may reduce this even further.

Octopus Flux is an electricity tariff with three rates for both import and export. It was announced by Octopus Energy in February 2023. You do not need an electric vehicle (EV) to use the Octopus Flux tariff. You can use it if you have an EV though, so it is a way to access much better export rates. It works best for households with both solar panels and battery storage, because they can avoid using any energy at the Peak rate (47.58p/kWh).

I moved us from the Octopus Go tariff to the Octopus Flux tariff on the 12^th April 2023 because it was very clear that the export revenue generated from our excess solar energy would easily cover the standing charge AND our electricity import costs each day. This means that Octopus are now paying me to use and export electricity 😎 In fact, the excess revenue from exporting energy will also cover my gas costs in the summer months too. My energy bills will be negative! 🤯

When you migrate to the Octopus Flux tariff, the import element is set up quickly. The set up of the export element can take a bit longer. In my case it took about 12 hours.

Note: Octopus Flux is a flexible tariff, so prices can change with wholesale price changes and it also varies by region. If you are on a Feed-in Tariff (FiT) programme then you would have to give this up and join a Smart Export Guarantee (SEG) scheme to benefit from the Octopus Flux tariff. This may or may not be financially beneficial as it depends upon your specific installation and your FiT rate.

The Downsides

Moving from the Octopus Go tariff to the Octopus Flux tariff initially seems like a problem for an EV owner like myself, because I had to give up the super cheap night rate of 7.5p/kWh from 00:30 to 04:30. In reality, it really wasn't being used much though because we have a Zappi smart EV charger that can charge our CUPRA Born with free solar energy. We were only using the cheap night charging a few times a month and the Octopus Go export rate was a flat 4.1p/kWh 🙁 Many people are on a later version of the Octopus Go tariff with a more expensive Go rate of 12.5p/kWh. Either way, the Octopus Flux tariff cheap night rate of 20.39p/kWh is not a significant increase when you factor in the potential gains.

The Octopus Go tariff cheap rate time period from 00:30 to 04:30 was more convenient for running things like our dishwasher. We simply put it on a 3-hour delay before we went to bed and knew is would start after 03:00 and finish before 04:30. The Octopus Flux tariff cheap rate period of 02:00 to 05:00 is less convenient. We only have an option of delaying 3 hours or 6 hours on our dishwasher, so the timing is more challenging.

The Rates

The Octopus Flux tariff daily standing charge is 42.01p/day and this covers both import and export.

Import Rates

Day rate 33.98p/kWh: This is the default import rate and it cover the parts of the day not within the 'Flux' and 'Peak' rates. It compares favourably with the Octopus variable tariff rates.
Flux rate (02:00 to 05:00) 20.38p/kWh: This is the cheapest time to import energy. Note that it costs less than you get paid to export during the day. This is important!
Peak rate (16:00 to 19:00) 47.58p/kWh: This is the most expensive part of the day to import energy. You want to avoid this as much as possible.

Export Rates

Day rate 22.98p/kWh: This is the default export rate and it cover the parts of the day not within the 'Flux' and 'Peak' rates.
Flux rate (02:00 to 05:00) 9.39p/kWh: This rate is irrelevant as you will never be generating energy and exporting at during this time period.
Peak rate (16:00 to 19:00) 36.58p/kWh: This is when you get paid the most for exporting energy. You really want to export as much as possible during this period, to earn as much as you possibly can.

Maximising Return

Based on the available import and export rates, the following 'rules' will give the best financial return:

Charging your battery to 100% during the Flux period from 02:00 to 05:00, when electricity will be at its cheapest (20.39p/kWh), appears to be the cheapest way to fill your battery. It isn't always better than using spare solar energy during the Day rate period though (22.98p/kWh) because of conversion losses. Because I have Enphase microinverters and an ac-coupled Tesla Powerwall these losses are the same for both methods of charging my battery.
Time shift as many loads and appliances as possible to use the cheap rate period (e.g. dishwater, washing machine, laptop/phone chargers, etc.)
Always export as much as possible during the Peak period of 16:00 to 19:00 by minimising use of heavy loads during this period (e.g. cooker, kettle, etc.).
If you can export energy from your battery during the Peak period of 16:00 to 19:00, then do it up to your DNO export limitation. Mine installation is G99/G100 limited to 6.63kW.

EV Charging

One of the challenges with the Octopus Go tariff is the relatively short 4-hour cheap rate charging window. This limits the amount of energy you can put into your EV to about 30kWh when using a standard type 2 charger like our Zappi smart EV charger. This means my 58kWh CUPRA Born will not get to 100% 'State Of Charge' (SoC) unless it started out above 50%. With the Octopus Flux tariff this becomes even more of an issue because the cheap rate charging window is only 3 hours long. This limits the energy per charging session to about 23kWh.

Note: Whilst the best solution financially is to charge your EV at night on the Flux rate, we have been trying run our car on 100% solar energy and the first 7500 miles in our CUPRA Born have cost less than £120. I need to change my way of thinking.

Solar Hot Water Diverters

Despite building my own Smart Home Solar Water Heater for £55, it simply doesn't make sense financially to use a device like this on the Octopus Flux tariff, when we can heat water using gas costing just 10.31p/kWh. We will always be better off exporting any spare solar energy and getting paid at least 22.98p/kWh for it.

It has been disabled whilst we are on the Octopus Flux tariff and we will look at this again when we change tariff for the winter.

Battery Storage

We have a Tesla Powerwall being installed very soon. On the Octopus Flux tariff it makes sense to charge your battery to 100% SoC every night using the Flux period. This costs 20.39p/kWh and is the cheapest way to fill the battery, when you will be paid more (22.98p/kWh) to your export spare energy.

Note: This is not always true. It makes sense with my system because I have Enphase microinverters which provide 230V ac and an ac-coupled Tesla Powerwall, so conversion losses are not a factor when charging the battery.

You also need to configure your battery to ensure you don't import any energy during the Peak rate period and get charged 47.58p/kWh for it.

Note: Charging an ac coupled battery to 100% each night is better for it because it means it doesn't get worked as hard between chargers. My Tesla Powerwall rarely drops below 70% SoC.

Note: My Tesla Powerwall will do all of the required energy management 'out of the box'. All you need to do is set the operational mode to 'Time-Based Control' and enter the Octopus Flux tariff details into the app. It will then intelligently control charging and discharging to maximise your returns on this tariff.

Summary

Whilst on the Octopus Go tariff for the first 12 days of April 2023, I paid Octopus an average of £2.28 per day including standing charges and factoring in our imports and exports. Since moving on to the Octopus Flux tariff, Octopus are now paying us £1.69 per day on average. This means we are currently £3.97 per day better off and this was before our Tesla Powerwall is installed.

The installation of our Tesla Powerwall will mean we basically import zero energy and completely avoid the Peak rate (47.58p/kWh) period. It will also mean we can maximise our exports in the Peak rate period, to get paid a lot more (36.58p/kWh). Going forward, we expect to get paid at least £150 per month by Octopus Energy for using and exporting energy and this should last through April to September, when I will think about changing tariff again for the winter months.

The financial loss between running an appliance at night on the Flux rate (20.39p/kWh) and using spare solar energy (22.98p/kWh) is small, so I do not feel guilty about running things like the washing machine in the morning because it is more convenient.

Energy companies are paying good export rates and introducing innovative tariffs like Octopus Flux, to encourage people with solar installations to help them even out the demand for electricity and to assist in handling the demand during peak periods. By exporting as much energy as I can and by earning as much as I can from it, I am doing as much as I can to help them avoid firing up another dirty power station to meet the peak demand. There is no reason to feel guilty about exporting 100's of kWh of clean, renewable energy each month. If I had a bigger roof on my house, I would do even more to help 😊

Downloads

I have put together an example Microsoft Excel spreadsheet, into which you can paste you 30-minute billing data downloaded from the Octopus Energy website. This will then calculate how much you have paid for imports and earned from exports.

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