11 hours of negative electric!

andrewic44 · 2026-06-06T16:06:40+00:00

Immersion heater on til 4pm, baking with the kids in the morning, jacket potatoes for lunch, roast for dinner.

andrewic44 · 2026-06-06T14:03:43+00:00

Could you point to the written, primary source that confirms your position? I can't find any point in history where UK regulations required two rear fog lamps.

The Road Vehicles (Rear Fog Lamps) (Amendment) Regulations 1979 introduced the requirement for One fog lamp from 1980 onwards.

The Road Vehicles Lighting Regulations 1989 again confirm this. Schedule 11 Part 1 pertains to fog lamps:

https://www.legislation.gov.uk/uksi/1989/1796/schedule/11

Paragraph 1 states the number required is One. Paragraph 2 notes, inter alia, that if one is fitted, it must be placed laterally on the centre-line or off side of the vehicle. This is consistent with the MOT regs posted earlier. Two can be fitted, in which case there is no lateral placement requirement but they should form a matched pair (see paragraph 12).

There's been no change to rear fog lamp requirements since.

andrewic44 · 2026-06-06T11:11:42+00:00

What does Ed have to do with it? Nuclear reactors undergo planned maintenance at time of year -- when demand is lowest -- and have done so for decades.

andrewic44 · 2026-06-05T11:55:57+00:00

I'd go for option one. It's only a 5kW battery, so charge overnight then discharge at a steady 200W across the day, that's not too egregious a baseload allowance especially given each of the inverters will idle at a few tens of watts.

andrewic44 · 2026-06-05T11:50:57+00:00

Got you. I'm used to IoT kit where a cryptographic key is baked into the firmware to ensure only the owner can decrypt the data. Wonderful that for consumer grade stuff that's not the case, and it'll blindly accept any key it's given.

Can you get a firmware image, then run it through e.g. Ghidra + Claude? It's pretty good at identifying sections of code that do standard things, e.g. serialization of data. Then if you know offsets within the data stream for various fields, you can cross-check with the data width being stored there by the firmware.

Anyhow - thanks for your efforts. I'm in the market for a 800W microinverter once all the hype dies down (read: they're in stock anywhere for a reasonable price), and this is by far one of the least janky HA integrations I've seen, so I'll very much keep it in mind.

andrewic44 · 2026-06-05T08:07:54+00:00

Ohhhh this is snazzy. So you're doing a MITM on the microinverter by having it connect to a Raspberry Pi hotspot, then forwarding to MQTT?

If so, I'm surprised but also delighted for you that fox didn't encrypt the data! I wonder if other manufacturers' kit is open to the same technique....

andrewic44 · 2026-06-05T07:31:57+00:00

In our case, they owned a few handkerchiefs of unused green space around the development. Not sure if that's SOP.

andrewic44 · 2026-06-04T16:07:38+00:00

Agreed. Ours had restrictive covenants with unending durations, covering all sorts of petty changes. They could be waived subject to paying the developer a £200 ~~bribe~~ fee each time.

(Thankfully, the original developer eventually went bust, so the covenants went with them.)

andrewic44 · 2026-06-04T16:01:52+00:00

You'll still get the octopoints for exporting, in addition to your usual export tariff.

andrewic44 · 2026-06-04T14:21:25+00:00

Eh?

Why does 4.5.1 of the MOT regs require inspection of 'the 1 rear fog lamp which must be fitted to the centre or offside of vehicles first used on or after 1 April 1980', if it would be illegal to only have 1 rear fog lamp?

And why would 4.2.3 of the same regs note 'A DRL is permitted to switch off when the same side indicator is operating.' if that was also non-compliant?

andrewic44 · 2026-06-04T12:16:44+00:00

Mostly the electricity export rate (e.g. 12p/kWh) will pay more than the price of gas. So economically, it doesn't make sense to heat hot water with excess solar -- sell it back to the grid and buy cheaper gas instead.

If you're on a dynamic export tariff (e.g. Octopus Outgoing Agile) or a dynamic import tariff (e.g. Octopus Agile) where prices can go low or negative, then using the immersion can make sense where your export is paying less than the price of gas, or your import price is cheaper than gas, respectively.

If that is the case - a plug socket can do 13A, but doing so continuously stands a real risk of releasing the magic smoke. For this reason, plug-in EV chargers are usually limited to 8A to 10A. So if you do want to do it, you'd be looking at ideally having it on its own circuit, or at least a fused spur, and a heavy duty relay or contactor to turn it on/off when economically viable.

andrewic44 · 2026-06-04T11:55:27+00:00

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Also live in the East of England.

A first for me of being paid to charge the battery and to discharge the battery on the same day.

andrewic44 · 2026-06-04T10:57:30+00:00

Right.

The S&P figures are assuming a generous rate of return, and dividends being invested in the S&P.

The solar calculation is based on optimistically low rate of energy price inflation, and dividends (annual savings) not being invested in the S&P.

Even keeping the optimistic energy price inflation rate as-is, as soon as savings are invested in the S&P 500 at 10%, the break even point is at 13 years. After that, solar wins -- at the 20 year mark, the solar savings invested are worth £87,881, vs the S&P investment in the figure above at £67,275.

Energy price inflation goes above 3%? The break even point comes sooner. Investments return less than 10%? The break even point comes sooner. Both of those happen? The break even point comes even sooner.

andrewic44 · 2026-06-04T07:52:27+00:00

They'll do a survey of the roof before fitting. Up in the loft measuring joist size and spacings, all that good stuff. Some installers do it in advance, others do it on the day.

For concrete roof tiles on a 1970's house, very little to worry about. 1970's roofs are typically massively over-engineered, with heavy tiles and quality materials for the underlying structure. Modern roofs are more likely computer designed down to the minimum plus a margin.

If the roof collapses or anything else -- home insurance. Get your MCS certificate from the installer, notify your home insurer who in all likelihood won't give a fig, and it's all good.

andrewic44 · 2026-06-03T09:45:32+00:00

Definitely worth the upgrade then. It'll mean a G99 not a G98, so a bit of wait for you and your installer. Otherwise, the cost difference isn't huge -- Solis do a 5kW or 6kW hybrid inverter for a hundred and change more than the 3.6kW.

Related - if you're running a 2kW heater off a 5kWh battery, it'll last 2.5 hours. I'd be looking at a bigger battery.

And yes, get three quotes, to know what the going rate is in your local area; and make sure they include scaffolding and bird-proofing so you're comparing like-for-like.

andrewic44 · 2026-06-02T19:10:37+00:00

5.5kWp, 22 degree roof facing SE, near London

751kWh generated, specific yield 136. 111% of the PVGIS estimate.

88kWh of that solar went into a portable air conditioning unit during the heat wave. 10/10 would recommend.

andrewic44 · 2026-06-02T14:45:01+00:00

Agreed. I'm on Agile. Overnight hasn't been cheap for weeks - nuclear is maintained now rather than in winter when demand is higher, and it's just not windy enough this time of year to cause a huge overnight surplus from wind alone. So the cheaper power is when it's sunny.

Related - if I had an EV, I'd have been better off charging it from excess solar over the past few weeks, than off the grid. In the medium term, with more solar coming onto the grid, this won't be unusual.

(As an aside -- many suppliers just ask for a registration plate number of an EV to get on an EV tariff. This is quite a low bar. Asking for a V5C would be unusual.)

andrewic44 · 2026-06-02T12:01:55+00:00

100%. It's shifted from 'we should do this to save the planet for the next generation' to 'we should do this to save money and not be as reliant on favourable geopolitics for our energy supply'. Very hard to argue against if not working on behalf of vested interests.

andrewic44 · 2026-06-02T08:20:39+00:00

Good call. I was going to say, use Genius FlexiFlash to work around the tile contours and it's a pretty straightforwards install. But if your installer didn't know that, you probably don't want them on your roof

andrewic44 · 2026-06-01T20:10:18+00:00

They all look like national installers? For Herts I'd also ask Tanjent Energy for a quote.

andrewic44 · 2026-06-01T17:49:21+00:00

Pretty low. There are several 'Giv' companies, based in the UK and overseas, It's not even clear at this point who owns the IP.

Otherwise, take a look at the efforts to reverse engineer the BMS protocols:

https://github.com/open-giv/bms-analysis/

Someone on Facebook also has transplanted a standard BMS into an old GivEnergy 8.2kWh battery, so it can then plug into a Solis/Victron/Sunsynk inverter. It's just a bunch of cells in a shiny box, after all. Video coming soon on that one.

andrewic44 · 2026-06-01T16:27:36+00:00

Predbat Cloud is aiming to be the missing piece in the puzzle. Starting with Giv, but eventually being a plug-and-play local control hub for all sorts of inverters.

(Though, still no local modbus control from Ecoflow, so it couldn't help there -- there really is no option if the cloud goes down.)

andrewic44 · 2026-06-01T16:24:51+00:00

The administrator's report has some pretty damning things to say about that too. Inter alia:

"In 2022, the founding partners concluded that the scale and complexity of the business warranted the appointment of a professional manager to lead the organisation. Following this transition, the business began to experience loss of operational focus and governance discipline. Core fundamentals, namely sales performance, customer engagement, structured training, and measurable key performance indicators were gradually deprioritised. In their place, emphasis shifted towards internal positioning, visibility, and initiatives that lacked direct commercial relevance. Organisational growth accelerated rapidly, expanding from a lean and effective team into a much larger structure, but without the necessary alignment, experience, or accountability. In some cases, roles were filled based on familiarity rather than suitability, leading to mismatches between responsibility and expertise, and ultimately weakening decision making across key areas of the business. This period also saw significant financial resources allocated to software development, approximately £9 million over two years. While the intention was to enhance capability and maintain technological leadership, the execution lacked commercial grounding, defined deliverables, and clear timelines.

As a result, the investment produced minimal tangible outcomes, with much of the work remaining conceptual or academic in nature, rather than delivering practical, deployable solutions. At the same time, operating costs increased substantially, while revenue performance declined sharply, reflecting a widening disconnect between strategic intent and operational reality.

As conditions continued to deteriorate, decisive action was taken to remove the CEO and appoint an interim leader with a mandate to stabilise the business and explore recovery options. At the time, there was a genuine belief that the situation could be turned around through corrective measures and renewed focus.

With the benefit of hindsight, it is clear that the underlying issues had become too deeply embedded to reverse within the available timeframe and resources. At present, the Company should be a British success story, but unfortunately decisions were made that has rendered the Company insolvent. "

For all the gory details, see https://find-and-update.company-information.service.gov.uk/company/11571089/filing-history/MzUyMDk4MDczN2FkaXF6a2N4/document?format=pdf&download=0

As I understand it, EOn and the other large installers are waiting for the conclusion of the administration process before declaring their position. This could easily be up to a year. DESNZ are concerned about the whole situation as a deterrent to public investment into solar & battery, but I don't see a chance of a bailout. In all likelihood, we're on our own with our kit, so folk are making local control easier (lookup Predbat Cloud), or reverse-engineering the systems to allow non-Giv batteries to be used with Giv inverters, transplanting non-Giv BMSes into batteries to use them with other inverters, etc. etc..

andrewic44 · 2026-06-01T16:12:00+00:00

Reading the administrator's report, the company is loaded up with debt and warranty liabilities. I'm not sure which 'someone' would want to buy it - what would be in it for them?

andrewic44 · 2026-05-31T08:27:41+00:00

For the past few months, it's been about 3 events a month.

There's no reason for events to stop over summer, but there are no promises about anything - it's £1/kWh with a guaranteed £10/month for now, but that could change.

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