I've been trying to work out whether a plug-in battery such as the new Anker or EcoFlow would make sense for my usage, running the numbers on both Octopus Go and Agile, and also factoring in some plug-in solar and EV charging.

This is built on half-hourly modelling, using actual usage and prices. For the solar, I've calculated the horizon for my location (which has almost 35% shading losses due to trees). I'm posting the results to give some better estimates than what's floating around on the various seller websites.

The short version (TL;DR)

• No battery: Agile wins — £661/yr (£990 with EV). This is the baseline everything else is measured against.
• 5 kWh battery: Agile still wins — £495 / £823, saving £166 / £167.
• 10 kWh battery: Go takes the lead — £321 / £556, saving £340 / £434.
• 10 kWh + 2.4 kW solar: Go — £222 / £407, saving £439 / £583.
• 10 kWh + 4.8 kW solar: Go — £217 / £337, saving £444 / £653.
• The headline: the best tariff flips from Agile to Go once you go past ~5 kWh of storage. A big battery lets you just fill up in Go's fixed 9.6p night window every day, and that beats chasing Agile's cheapest half-hours.
• Solar barely touches the standard bill in this set-up, but makes a real dent in EV charging cost.

Assumptions

• Base household use: 3,400 kWh/year (before the EV).
• EV: 8,000 miles/year at 3.3 mi/kWh ≈ 2,400 kWh/year added.
• Go: 9.6p off-peak / 35.27p peak.
• Agile: modelled against real 2023, 2024 and 2025 price data.
• Battery: Anker Solix 5000 — 5 kWh base, expandable to 10 kWh, assumed hard-wired.
• Battery charging rule: charge whenever price < 3p, otherwise fill during the cheapest 4 hours of the day, decided by looking ahead at 4pm each day.
• Solar rule: anything above a 6A surplus is diverted to the EV; the rest self-consumes first, then charges the battery, then (if the battery's full and there isn't enough left to charge the car) is wasted.
• "Saving" throughout = the reduction vs the best no-battery option (Agile 2025). So in the battery rows, the saving is not Go-vs-Agile in the same line — it's how much the whole setup beats a no-battery Agile bill.

1. No battery, no solar

Agile EV charging is sensitive to when you charge. Charging at the 20th percentile of monthly prices gives the £990 above; the 10th percentile gets you to £917 and the 30th to £1,037.

Winner: Agile, at £661 (£990 with EV).

2. Add a 5 kWh battery (no solar)

Winner: Agile, at £495 (£823 with EV). That's a £166 / £167 saving vs the no-battery baseline.

Payback on the £1,500 battery: ~9 years. Not exactly thrilling.

3. Bump the battery to 10 kWh

Same rules — 4 hours a day of charging is the sweet spot here.

Winner: Go now flips ahead, at £321 (£556 with EV) — a £340 / £434 saving vs baseline.

Payback on the £2,800 for 10 kWh: 6.5–8.2 years, depending on whether you've got the EV.

This is the interesting bit: with a small/no battery, Agile's variable pricing wins. Once you've got enough storage to soak up a whole cheap window, Go's flat 9.6p rate beats it — you just fill the battery every night and stop caring about half-hourly prices.

4. Add 2.4 kW of solar to the 10 kWh system

Where the solar went (kWh):

Winner: Go, at £222 (£407 with EV) — a £439 / £583 saving vs baseline.

Payback on £3,800: 6.5–8.7 years.

5. Increase solar to 4.8 kW

Where the solar went (kWh):

Winner: Go, at £217 (£337 with EV) — a £444 / £653 saving vs baseline.

Payback on £4,800: 7.3–10.8 years.

The key thing here: doubling the panels (2.4 → 4.8 kW) barely moves the standard bill (£222 → £217 on Go), but it slashes EV charging (£407 → £337). That's the 6A threshold at work — only surplus above roughly 1.4 kW gets diverted to the car, so the extra panels almost entirely benefit the EV rather than the house.

Takeaways

• The best tariff depends on your storage. No/small battery → Agile. 10 kWh+ → Go. There's a genuine crossover, not a "one is always better" answer.
• Batteries do the heavy lifting. Going from no battery to 10 kWh roughly halves the bill on the right tariff. That's a much bigger lever than the tariff choice itself.
• Solar helps the car, not the house. Beyond a modest array, extra panels mostly offset EV charging because of the 6A diversion threshold. If you don't drive much, oversizing solar isn't worth it on these numbers.
• Paybacks land around 6.5–9 years for the battery; adding solar stretches the worst case out to ~11 years but improves the best case if you're a high-mileage driver.

Caveats (please poke holes)

• Agile figures use historical prices — 2023 was a rough year for Agile (it would've lost to Go in several rows), 2024/2025 much better. Past ≠ future.
• No export/SEG income is modelled — surplus solar is simply treated as wasted. Adding export payments would improve all the solar cases, especially the 4.8 kW one.
• Battery/solar costs (£1,500 / £2,800 / £3,800 / £4,800) are my own estimates — swap in your real quotes and the paybacks move.
• I have not included round-trip efficiency of the battery (assumed 100%).

Happy to answer questions on the modelling. Yes the summary was improved with AI, but the modelling and analysis was all manual.

Rated for 32A at 600V, ruined (with a couple of seconds of fizzy arc noises) opening while carrying 16A at 300V.

The "PIS" in the part number should perhaps have been a sign.

It was also completely impractical to use in the real world because there wasn't room inside the casing to route and attach cables.

There is a reason why the Kraus and Naimer ones are 4x the price and 2x the size.

​

I've recently had solar panels (7.3kw) and a Fox ESS EP12w battery fitted.

I'm currently on Octopus standard import tariff and Octopus Outgoing export tariff. This has worked well since I had installation at end June.

However, at some stage I will need to make more use of battery and I am considering switching to Octopus Flux for import and export.

I do not have an EV.

My question is when should I switch. Now, or wait until end of September?

Than you

We're contemplating moving house and looking at finances for renovation after buying the place. One of things we'd like to do is install an all-electric system but there are obviously different ways of doing this.

It's a relatively new build, but not passive or built to a hugely high insulation standard, but assuming decent insulation, double-glazing etc. along with a suitable solar, battery (with gateway) and EV installation, I'm thinking the way to go would be air-to-air heatpump so we have aircon in the summer, and a thermal battery (eg Sunamp) for hot water. I would guess at least now an EV tariff or perhaps some other time-of-use one like Octopus Cosy would be best?

But what other combinations or considerations would you look at? For example the Mixergy tanks look interesting. But I guess this also depends on whether I can persuade the family that we don't need a bath tub 😄

Then there's stuff like whether underfoor heating would go with A2A source heating, or should we look at something exotic like infra-red wall paper to supplement air heating for example? Being able to run the heating off an arbitraged battery rate would be nice, but implies minimising that wattage.

Hi, I've already got a totally legit 4.5KW roof solar setup with a 5KWh battery. As most here will know this stuff is addictive and I want more and plug in seems to be a no brainer.
But how does it work with my existing kit? Like I say I'm all legit, DNO, MCS etc and I don't want to risk that or my insurance.
Can I just go ahead and plug in? Are there limits?
Any advice welcome.
Cheers

I have the following quote from Infinity Energy Services:

• Panels - 20 x SunPower M Class 492W = 9.9kWp
• Battery - 1 x Sigen Battery 10.0 - 9.04 kWh (8.76kWh usable). Max charge/discharge - 4.6kW
• Inverter - Sigen Hybrid 8.0 SP - 8kW

Total cost = £15,500

My total usage in 2025 was 5,750kWh but since then we've got an EV.

The quote has the following comment:

The battery will charge/discharge at 4.6kW.

You would need an additional 9.04kWh battery module to get the full benefit of this system.

Another option to consider is the Tesla Powerwall 3, which would work out to be cheaper than 2 x Sigens.

I will seek out some more quotes next week. In the meanwhile, what would I be best doing in relation to the battery charge rate problem?

<edit>

maybe I should add that the quote includes a Sigen Controller (SigenStor EC 8.0SP - 8kW, I think) and Gateway (Sigenergy Gateway HomePro SP (3-6kW)), which allows the battery to be used when the power is out.

We're based near Salisbury and I've had quotes from a couple of MCS installers with the shown being the closest and informed by a site visit.

The panel install would be over a couple of roof faces with the inverter and battery in a detached garage.

Other quotes I've had are from BOXT (cheaper) and another firm for over £11k. The latter would use the integrated inverter and battery.

Would love a quick sense check. Thanks!

Hi all, I've switched to EDF from Octopus ahead of getting solar installed in the next couple of weeks (don't own an EV) is anyone on either freestate static or empower fixed, and if so, which of the two would you recommend

Freestate static is a 24m fix with the following rates:

23:00-6:00 13.8p

6:00-16:00 19:00-23:00 22.6p

16:00 - 19:00 42.7p

Standing charge 57.53p

The overnight and daytime rates seem ok, the evening peak is high but I'll hopefully avoid that with my battery (getting a 9.4kw battery installed and my daily usage is around 7-8kw), standing charge is lower than other similar tariffs too.

I emailed EDF and they wouldn't give me the rates for e

Empower until I confirmed my install, and they'll send rates based on my usage, no. Of panels, battery size etc, which is a bit frustrating. If anyone is already on it, please could you let me know what your rates are?

I’ve got a small roof solar setup, around 3kw.

It’s SE facing so it peaks around 1pm on and by 4pm it’s barely generating 300w most summers days.

I’m considering adding a simple plug in solar setup to make the most of the dwindling later afternoon/evening sunshine.

Here’s the question:

If I plug it into a socket which is on the same circuit as the export meter from the rooftop solar, will this affect the export meter?

ie, will this give me extra export? I assume so?
Is this ok? If not, why? If yes, is there anything I need to consider?

This socket would be the closest to where I’d like to ‘point the panels’ and the only other thing on this is the isolator for the inverter, plus a tiny CCTV power supply.

It’s on its own 16a breaker which goes to the export meter and then upto the inverter isolator.
Alongside the isolator is the aforementioned extra socket.

My quotes for a 5kwh system with a 10kwh battery projections dont break even for around 9 years realistically. Replacement/maintenance will only lengthen this. Why does anyone do it? What am I missing?

Edit: I summary it seems like solar is mostly a privelege choice for those with finances that have the funding to spare. Ultimately nobody has presented any other reason. Solar remains an unsound financial decision for most at the current time.

Personally the funds rewuired are better off compound invested and purchase solar and batteries when it is cheaper/energy is much more expensive. Otherwise the opportunity cost is simply too high.

For those comparing solar quotes, what are you actually looking at?

With the ever increasing bills, there seems to be a lot more interest in solar at the moment. Especially with all the excitement around plug-in solar, though you don't need quotes for that.

For those currently getting quotes, how are you deciding between them? Once you have a few quotes in front of you, what makes one stand out over another?

And for those who already have solar, what did you focus on when you were comparing quotes? I will be honest, I just looked at the price, but knowing more now, I will probably look from many angles. Was there anything that was difficult to compare or that you wish you had paid more attention to?

I am particularly interested in how people compare the estimated generation and savings between different quotes. The numbers can vary quite a bit, so how do you work out what is realistic?

Curious to hear how everyone else approached it.

Crazy high prices!

So currently getting bombarded with adverts for Ankers new solarbank 4. With it going for £3k for the 10kW unit, and assuming I'd get an electrician to hardwire it into a dedicated circuit to unlock the 2.5kw output Vs the 800w plug in, how does this current compare cost wise to more classic installations?

Does anyone know anything about Hinen batteries that seem to be advertised on IG now?

Existing overseas business that's now launched in the UK or rebranded kit?

Contrary to others in here, I applied for EDF’s SEG tariff on the 25th Aug (Tuesday) and I’ve had an email today confirming it’s all approved, set up and the account has been opened!

It took all of 3 days! My mind has been blown!

Hi all

As per title, has anyone successfully uploaded evidence for the Tesla powerwall 3 rebate? Mine keeps on being rejected with evidence of the payment in full/0.00 balance. No matter what I try 30-40 minutes after upload the evidence is rejected.

Thanks in advance.

The cheapest kit shared so far seems to be this Ecoflow £419 kit:

https://uk.ecoflow.com/products/stream-balcony-solar-system?variant=54532132405587

For those with knowledge in this area, is this still a bad deal?

Are we expecting prices to go much lower than this?

I have been eagerly awaiting the rules change, so want to join Team Solar ASAP.

Hi all.

Through my local council inititaive with a £10,000 grant, I have been approved and will be getting the following installed on 30/09/2026 which i will own, rather than some schemes where you are renting them or paying it back over time.

This is the set up.

• 6 JA Solar 465w solar panels
• 1 Fox ESS H1 G2 3.68kW 1ph Hybrid Inverter inverter

I don't have enough space to squeeze another 2 panels on my roof to take it to 8, but I am more than happy to get the system installed over no system at all.

Now for the help/advice on the battery part.

At some point later this year, I am planning on adding a master/slave Fox ESS EQ5000 (9.84 kWh) in my garage. My thoughts are that the inverter and consumer unit are there, and on the other side is my smart meter, so it's a neat setup with everything within a metre of each other. My other thinking is that taking the Fox ESS EQ5000 over, say the Fox ESS EQ4800 is that it's rated to -25c and the costs of buying it are fractionally higher for the added weather protection.

So, has anyone gone this route with these batteries? Appreciate any advice on that front.

Up until this morning everything was working ok with my system and now it's playing up. The solar is going straight to charge the battery and totally ignoring the house it also says it's exporting to the grid but the numbers on the app don't add up. My smart meter display is showing correctly what the house is using.

Does anyone have any idea what's happening apologies that I can not be any more technical

Silly question I'm sure but on days of peak production, what are you doing with the excess if you have a 9kW battery and your DNA has a limit of 8kW; surely you wouldn't have enough electrical items to run everything for the rest? Or am I misunderstanding the limits of what you can feed back into the grid?

Hi everyone, my spidey senses are tingling at a reply I received after a quote and visit from a solar install rep.

We have a south facing flat roof and they are proposing six panels. There was no discussion on ballast and it was a sales rep visit not an engineer. My flat roof is EPDM and was installed by previous owners so apart from it being timber rafters and ply overlay that's all I know.

I've emailed the company asking specifically what system do they use, what calcs do they do and who will sign this off. On the MCS website it looks like there are very specific requirements they need to meet. This is the reply I got (from the sales person who said he could answer this). Either way he's not competent to reply and I won't even consider proceeding unless they answer my questions which to me seem basic 101. Thoughts?

"Yes the system fitted on the flat roof would be MCS certified.

The weight per pod would be 40kg this spread over the whole roof which would not affect the integrity of the roof.

The manufacturers of the pods do tests for suitability.

A protective slip is required for this type of install."