Is anyone force-charging their solar batteries using Octopus overnight rates?

itm2

We're considering solar (again), but only have room for 6 panels on our roof. Since we are high consumers (an average of 18.5 kWh per day, based on annual totals), and are also at home during the day, we would like to optimise the financial benefits by force charging the battery from the grid overnight, when Octopus's Agile rates are lowest, then drawing on the battery during the peak hours of 4pm - 7pm.

Does anyone have any experience of doing this? I'd be interested to hear what sort of equipment you have, and how effectively it has been working.

Vortigern

We are currently on Octopus Intelligent Go, charging both house and car batteries overnight and during other cheap slots. Easy to manage but you'd need an electric vehicle.

It's probably harder to manage with Agile's half-hourly price changes.

Slinky

We have solar and batteries; currently we charge overnight on Economy 7 rates between 12.30 and 7.30am. Previous winter I had Agile, but our Solis inverter only allows programming of 3 charging and 3 discharging slots at a time, so I had to fiddle and diddle the settings each day to take as much advantage as I could with the cheap rate slots. This winter has been less stressful as the 4-7pm slot, whilst higher than the standard day rate, is nowhere near close to Agile's rates. This is the only daypart we're likely to be using power off the grid when multiple appliances are on at the same time when cooking dinner. As it is, 92-94% of our import is at night rates, which for us currently is just under 12.5p. I was quite relaxed about charging more than we needed as any export was covering the cost of the import when it was 15p, but of course that's now dropped to 12p.

As we come into the lighter days, I'll reduce, hopefully stop the overnight charging.

ETA we have about 10kw batteries and only use about 8kwh per day.

JKenH

I am on Octopus Go and have a Tesla PW3 battery which currently is charging to 100% every night. The battery does top up with solar if it thinks that I’ll need it. I do fine tune the charging a bit but don’t really need to - it is essentially fit and forget once you have programmed it with your tariff.

NedS

The main consideration you will have when using Octopus Agile is automating the charging based on the cheapest periods, as the prices change half-hourly, daily (as you know).

So unless you are happy to just always assume Agile prices will be best for a certain period overnight (e.g, 1am-5am) and set the battery to charge regardless, you will need some way to automate the process or purchase equipment that has the facility to integrate the Agile tariff automatically so the battery knows the half hour pricing and can decide when it is cheapest to charge.

So it's very possible, but will depend on the battery/inverter system you intend to purchase.

QrizB

I'm another with my EV on IOG. I charge my he battery to 80%-ish overnight. Once we get enough solar to fill the remaining 20% the rest is exported.

Clive_Woody

I set my house battery to charge to full every night on cheap rate all year round. During the sunny months my panels top up the battery and then export to the grid. I get a higher rate for export than I do for charging at night so I look to optimise my export by keeping my battery charged at night so any 'spare' electricity gets sent to the grid.

pete-20-11

I let PredBat on Home Assistant decide, but generally it's better to fill it up rather than end up with an un-forecast cloudy day and run from the grid on IOG peak rate.

itm2

I've just discovered the Home Assistant / Octopus integration (I'm a Home Assistant user). I'm wondering whether Home Assistant would be a better way of managing the batteries than leaving it to the Octopus "Intelligent" product.

Any views?

NedS

https://forums.moneysavingexpert.com/discussion/comment/81920500#Comment_81920500

It depends which Intelligent product you are talking about - IOG or IOF?

To be eligible for IOG, you need an EV and compatible charger. Do you have one?

To be eligible for IOF, you need solar and a compatible battery. IOF hands control of the battery over to Octopus, for which you are compensated by substantially higher rates (for export). You should not also try to control the battery yourself, but rather just leave Octopus to get on with it.

There are a few online tools to help you evaluate which Octopus tariff may be best for your own personal circumstances, as everyone's circumstances will be different. Even then it is impossible to compare against a tariff like Agile as you have no clue what the prices may be next week, so all you could do is compare against what the prices were last week/month/year and assume they may be similar going forward.

itm2

Thanks. I don't have an EV (yet), and solar is currently at the feasibility stage.

Is there any historical indication as to whether IOF provides better pricing that Agile (e.g. over the last year)?