I am on Octopus flux. Is it always worth importing electricity overnight in the cheap period? Would it depend on if the following day is sunny and my battery could be 100% by mid morning by solar alone. Would I have wasted money by importing the night before? Or would I then just be exporting back to grid. I can't work out the sums easily. Any simple answers? Thanks
Yes, if the battery is full and your house is satisfied, excess solar will be exported. Assuming your input unit rate is lower than your export unit rate, you'll be making a small profit on your export. The other benefit is in the evening, you'll avoid more costly import unit rates as you'll be using your full battery until depletion.
sarah_jane in my region, import rates are around 16p, 27p, 38p, and export rates are around 4, 10 and 28p.
So importing overnight at 16p and then having
to export excess daytime solar at 10p is potentially wasting money. But not importing enough, and having to use daytime import if it turns out to be less sunny than expected might be worse. It's unfortunately not easy.
How big is your battery, and what is typical daytime consumption: daytime, peak (4pm to 7pm) and evening?
sarah_jane I infer from an older post that you have an EV. Depending on size of pv and battery, Go tariff might be simpler to manage, since it's always optimum to fill battery overnight and export solar at any time of day.
sarah_jane as @dd says, with the way the Flux rates are at the moment, it is not worth you importing overnight UNLESS the next day is going to be a poor solar day and you won't fill your batteries sufficiently to get you through to the next overnight cheap period
So depends on your solar panel size and your typical house load
You can create a free account on solcast.com.au to forecast your daily solar
We do import during the Flux window from 2am to 5am, but I’ve set a battery charge limit to cap it at 60% state of charge [we have two 9.5kWh batteries, so 60% is 11.4kWh]. For us, this strikes a good balance - it leaves enough in the battery to cover the day if solar generation is low, while still keeping room to store excess energy if generation is good.
I use Home Assistant and previously experimented with dynamic charging based on Solcast generation forecasts, but the predictions weren’t reliable enough. So I settled on a fixed 60% limit, which has worked better in practice.
It only works in your favour if you import during the flux rate and export at the peak rate. The old plan of full your boots and let excess naturally export doesn’t work with the current rates.
Move to Go and it does. You can import for 8.5p and export all day at 15p. So that plan makes sense.
With an EV you can get even better with intelligent go but you have to hand off control.
Guybrush-Threepwood With an EV you can get even better with intelligent go but you have to hand off control.
This is not correct. With IOG you need to allow Octopus to access your car or charger, but you can choose not to allow them any control.
Need a bit more info from you. Do you have an EV? Do you have a heat pump? What size batteries/ solar do you have? Simple answer is, there isn’t always a simple answer.
In my case I have an EV, no heat pump. Dual 5kW gen3 hybrid inverters, 38kWh of batteries. Generate 5,600kWh a year from solar, No automation. I’m on Intelligent Octopus Go; Charge the batteries every night (all year round) to 100% for 7p a kWh, export all solar, then export what’s left in the batteries in the early evening to get them to empty (4%) at 11:30pm. All at 15p fixed export.
I (IOG) charge the car overnight whilst the home batteries are charging (from 23:30–>05:30), I set the car to be “ready by” 05:30am. All import is at 7p.
I very rarely get any slots outside the core IOG 6 hours but if I do they are in the evening and I just hit the quick play button to charge the batteries at the same time (so they aren’t dumped into the car!). This may be because 99% of the time I’m operating the car between 20-80%, so it rarely needs extra slots to get to 80%. They do happen sometimes but it’s extremely infrequent for me and only mildly inconvenient when it does.
Last 12 months to date my electricity bill including standing charge was -£150. ie in credit (including savings sessions of about -£20).
My average 12 month import rate is currently 7.18p. And very slowly decreasing.
My average off-peak import is 99.5% currently and
Very very slowly increasing.
I think I can realistically get close to 99.8% off peak by the end of the summer (as the old data drops away after the technical difficulties I had last summer).
I also use “Octo-Aid” which is a free app that’s brilliant for keeping track of your import/ export usage and total costs. I recommend checking it out. It might be quite useful for you. I must add that don’t try and use ANY of the compare apps for comparison with IOG and your current tariff. It won’t be accurate, as they just split your total daily usage into thirds and assume 1/3 is at 7p and 2/3 is at the peak rate. This won’t ever be the case and is extremely misleading.
Your costs will be far far cheaper than what they come up with if you have solar and batteries !
Hope that helps and Good luck.