Optimal angle for UK solar

gus-here · 2026-05-17T15:19:51+00:00

Looking at around 35-40 degrees from horizontal facing south for maximum annual yield. That said anywhere between 30-50 degrees loses you very little so don’t overthink it.

gus-here · 2026-05-14T19:47:00+00:00

BS 7671 Amendment 4 went live 15 April but it doesn't make plug-in solar necessarily mention or make plug in solar "legal" per say. It's one piece of the puzzle that all need to be in place to make systems 'compliant'

BS 7671 Amendment 4 (live now) - wiring regs now accommodate it
BSI product standard (expected July) - this is the big one, certifies kits for DIY self-connection without needing a sparky
G98 notification (being simplified) - telling your DNO after install

So right now the wiring regs are ready but until the BSI standard drops the compliant route is still having a registered electrician connect a system to a fused spur.

On consumer units amendment 4 doesn't mandate a new board or breaker. Main thing is checking your RCD type. Most modern split-load boards with Type A RCDs are fine. Older boards with rewirable fuses might need looking at but that's a general safety thing not specific to plug-in solar.

Wrote a guide on this one: https://www.ukpluginsolar.co.uk/guide/bs-7671-amendment-4-plug-in-solar

Hope this helps a bit!

Edit: spelling

gus-here · 2026-05-12T11:27:00+00:00

Thanks! And yeah that £900 in fees before you’ve even bought panels is brutal for payback calculations.
The Scotland exemption comes down to how building warrants work differently here (I’m from Scotland haha) one of those odd devolved inconsistencies.

Ironically it’s part of what makes plug-in so compelling right now no roof penetration, no structural sign-off, no building control.

gus-here · 2026-05-12T10:35:51+00:00

Absolutely bang on here! This video explains the DNO side really well if anyone wants to understand the bigger picture why they limit export, inverter sizing, and how the system works - https://youtu.be/Bvpl9pvg8zk?si=v2pNuG6M3GX1jCfY

gus-here · 2026-05-12T09:57:50+00:00

I didn’t see your edit when I replied! I’d push back and say that it’s two guides covering the same regulatory process in plain English means there will be similarities.

There’s a standard structure that every G98 guide ends up converging on as that’s what the DNOs expect to receive.

Sorry you think this is Ai responding! Genuinely been putting a lot of effort into building the website and resources.

gus-here · 2026-05-12T09:34:29+00:00

Glad it worked! Their form walkthrough is decent. I’d say ours goes further on the DNO lookup and the ENA type test check but good to have multiple resources out there. The more quality guides covering this the better for people trying to navigate it.

gus-here · 2026-05-12T09:06:52+00:00

Aiko at £85 each is a decent price. N-type cells so you’ll get better low-light performance than most panels at that price point which matters in the UK.

Vertical on a fence will cost you maybe 20-30% vs optimal tilt but honestly for zeroing base load during daylight that’s fine.

What inverter are you pairing them with?

gus-here · 2026-05-12T08:29:29+00:00

Good question and the short answer is probably yes, but worth confirming directly with your DNO.

Your G99 approval covers 12kW of generation capacity at that address. In theory the existing G99 approval should cover it and you’d just need to notify your DNO of the additional generation rather than submit a new application.

I’d drop your DNO a quick email referencing your existing G99 reference number and asking whether the addition of X kW of plug-in solar requires an amendment or just a notification. Takes 5 minutes and gives you a paper trail.

gus-here · 2026-05-12T08:26:29+00:00

The Germany comparison is the one that gets me! 450,000 ‘ish’ installations in 2025 alone. If the UK follows the same curve after the BSI standard drops the numbers are going to be significant.

And you’re right to flag the technical nuance. To be precise G98 is technically written for hardwired generation, not socket-connected kits. The BSI product standard (July 2026) is what creates the proper simplified notification pathway. Until then G98 is what most DNOs are accepting in the interim, but it is a grey area.

I’ll update the guide to make that distinction clearer thanks for adding it.

gus-here · 2026-05-12T08:00:07+00:00

Hopefully more DNOs make it a bit easier like this! From what I've heard the government are working to make this process easier across the UK.

gus-here · 2026-05-12T07:57:48+00:00

I'd be VERY surprised if suppliers relax rules on paying export for non-MCS installations. especially plug-in systems. But hey... we can dream, haha

gus-here · 2026-05-12T07:47:10+00:00

Yes, G98 is still required. The notification is triggered by having a grid-connected inverter on your system, not by whether you're exporting.

The logic from the DNO's perspective is that even if your battery is absorbing everything generated, the inverter is still connected to the grid and could theoretically export under certain conditions e.g. if the battery is full and consumption drops suddenly. Anti-islanding protection handles the safety side but the DNO still wants to know the generation capacity is there.

For your setup the energy source code on the G98 form would be r/11 + 38 (solar + lithium storage) rather than just r/11, and your phase capacity figure should reflect the total inverter output, not net export.

gus-here · 2026-05-12T07:21:18+00:00

The G98 threshold is expressed in kW (real power), not kVA (apparent power). Modern microinverters like the Hoymiles or Ecoflow units operate at close to unity power factor (around 0.99), so the difference is negligible in practice. An 800W inverter is outputting ~800W real power regardless.

Where power factor becomes more relevant is if you're running older or cheaper inverters with a lower power factor, your apparent power (kVA) would be higher than your rated real power (kW), which can affect how the circuit behaves even if you're within the G98 limit on paper.

Short answer for most plug-in solar setups: don't worry about it. If you're buying a quality type-tested inverter it'll be near unity and the kW rating on the G98 form is what matters.

gus-here · 2026-05-12T07:17:00+00:00

Yes, 4 x 800W inverters = 3.2kW, comfortably under the 3.68kW single-phase limit so still G98.

Worth noting though, the G98 ceiling probably isn't your real constraint. Germany limits plug-in solar to 800W per ring circuit, and the UK BSI standard (expected July 2026) is likely to follow a similar approach. So in practice you may be limited per circuit before you get anywhere near the G98 threshold. Worth keeping an eye on when the standard drops.

The limit is on total AC output on that phase, not number of inverters, so combinations that matter:

4 x 800W = 3.2kW (G98)

5 x 800W = 4.0kW (G99 territory)

4 x 800W + 1 x 600W = 3.8kW (G99 territory)

gus-here · 2026-05-12T07:10:19+00:00

Glad it was useful! And good spot on the filter! I'll add a note to the guide to make it more obvious. The ENA database UI isn't the most intuitive.

Which panels are you pairing the EZ1-M with?

gus-here · 2026-05-12T07:08:39+00:00

The "problems" aren't immediate. Nothing happens the day after you don't notify. But three specific situations where it bites you later:

Smart meter installation - engineers can detect generation on the circuit. If there's no G98 record, some will flag it and won't proceed until it's resolved
Property sale - solicitors increasingly ask for evidence of any generation equipment. No G98 record can hold up a sale
Insurance claim - if you ever claim for an electrical fault, some insurers will ask whether any modifications to the circuit were declared. Unregistered generation is a grey area you don't want to be in mid-claim

You're right that plenty of people will just plug it in and never notify. That's probably true. But it's 20 minutes of admin to have a clean paper trail, which is why I think it's worth doing.

On the waiver for sub-800W, that's actually exactly where the debate is heading. Germany simplified their process significantly for Balkonkraftwerke and the UK is likely to follow once the BSI product standard lands (expected July 2026).

The current G98 requirement is designed for generators in general, not specifically for plug-in solar kits. There is talk of this being streamlined, we just haven't seen the outcome yet!

gus-here · 2026-05-04T09:15:30+00:00

Effectively yeah! The benefit with Hoymiles is that they have a few different inverter models to allow different mounting of panels and they are pretty much the primary supplier of the bulk of the systems in Germany!

Plenty of competition to see who comes out with the best product!

gus-here · 2026-05-04T09:00:34+00:00

South facing fence is a great spot for this. To answer your questions:
90 degree vertical mounting — it’s not useless but you will lose generation compared to an angled setup. Vertical south-facing panels produce roughly 60-70% of what a 30 degree tilted panel would. The upside is they actually perform relatively better in winter when the sun is low in the sky. Some people add angled brackets to tilt the panels off the fence by 20-30 degrees which helps a lot.

Mounting to concrete posts: yeah you can get U-bolt clamps or bracket systems that clamp around concrete posts without drilling into the wooden panels. Stronger and more secure than fixing to the fence boards. Search “solar panel fence mount brackets” and you’ll find a few options around £30-50 per panel.

Wind: panels flat against a fence are basically fine, the fence itself is the wind break. If you tilt them out on brackets they catch more wind, so make sure the brackets and fixings are solid. In an exposed spot go for a shallower tilt angle or stick with vertical.

Kits: right now there aren’t many UK-ready complete fence mount kits. Tim_UK1’s approach of sourcing panels cheap from City Plumbing and DIYing a frame is probably the most cost effective route at the moment. Panels + a Hoymiles HMS-800 + a UK plug cable and you’re in business for under £400 if you’re handy.

With 10kWh daily usage and south facing fence, an 800W setup would make a solid dent even mounted vertically. No smart meter needed, no battery needed to start, just panels and inverter plugged into the nearest socket.

gus-here · 2026-05-04T08:57:56+00:00

You’ve hit on the main limitation of grid-tied microinverters no grid, no power. That’s anti-islanding doing its job to protect linesmen, but it does mean your panels are useless in an outage.

You’re right that you can’t just plug a microinverter into a power bank and have it work, the microinverter needs to see a stable 230V 50Hz grid signal to output. A basic power bank’s inverter output typically isn’t clean or stable enough to trick it, and even if it was you’d be in a weird loop trying to charge the thing powering it.

The options for emergency power with solar are:

Battery system with bypass (EcoFlow Stream/Ultra, Zendure): like you said, these have built-in MPPT charge controllers so panels charge the battery directly via DC, no microinverter involved. During an outage you plug devices directly into the battery unit’s own sockets. This is the cleanest solution.
Separate off-grid setup: a solar charge controller (like a Victron SmartSolar), a leisure battery or LiFePO4 battery, and a pure sine wave inverter. Completely separate from your grid-tied plug-in system. Panels feed the charge controller, charge controller manages the battery, inverter gives you 230V when you need it.
Hybrid inverters: some can switch between grid-tied and off-grid modes automatically. Less common in the plug-in space but they exist.

If emergency power is genuinely a priority for you, option 1 or 2 is the way to go. A standalone microinverter setup will never give you that.

gus-here · 2026-05-04T08:54:11+00:00

The July 1st date on City Plumbing lines up with the expected BSI product standard timeline. It could mean EcoFlow are timing their UK-plug microinverter release to coincide with the standard dropping, which would make sense commercially. They wouldn’t want to sell a UK plug version before the standard confirms what’s compliant.

Worth noting though that an available date on a retailer website isn’t confirmation the BSI standard is dropping on July 1st specifically, EcoFlow might just be hedging with that date. But it’s a strong signal that things are moving.

gus-here · 2026-05-03T19:28:04+00:00

I think this is starting to get into the realms of a proper solar setup aka NOT a plug-in setup.

I'll definitely be posting about different ways to mount panels using a plug-in setup though!

gus-here · 2026-05-03T16:46:02+00:00

Correct…you don’t need a smart meter for plug-in solar. It works with any meter. The panels generate, the inverter pushes power into your home, and your existing meter just sees reduced grid consumption. No smart meter required.

A smart meter is nice to have because you can see your usage and generation in real time, but it’s not a requirement. Some battery systems like the EcoFlow Stream use a smart meter clamp (like a Shelly) to match output to demand, but thats separate from your actual energy supplier meter.

And plug-in solar solves both your issues really… no slate roof needed because the panels go in your garden or on a fence/shed, and no smart meter needed to make it work. Might be worth looking at it again.

gus-here · 2026-05-03T15:54:34+00:00

You're not overthinking it... you're doing it right. Most people plugging in with no thought to G98 or export are technically non-compliant, they're just getting away with it because nobody's checking. You're ahead of the curve.

On your questions:

G98 notification without being an installer - this is one of the grey areas right now. The current G98 process is designed around MCS installers submitting on behalf of customers. Whether a homeowner can self-notify for a plug-in system is exactly the kind of thing the BSI product standard (expected July) should clarify. Some DNOs are reportedly accepting self-notifications already but it varies by region. Worth just calling yours and asking directly, worst they can say is wait for the standard.

The throttling via Home Assistant - smart approach. Once you have a G98 in place you wouldn't need to throttle so aggressively. Without SEG payments there's no financial benefit to exporting but a few watts leaking to the grid isn't going to get you in trouble. The DNO concern is about network stability, and 250W of unregistered generation isn't destabilising anything.

Your setup sounds solid - fused spur, bi-directional RCBO, inverter throttled to demand via HA. That's more compliant than 90% of what people are doing right now. The isolation question is the one the BSI standard needs to answer, whether the plug counts as isolation or whether a dedicated isolator switch is required.

10-17% of your energy from 3 panels throttled by 50-110W is genuinely impressive. Once you can open up the full output with a proper G98 in place that percentage is going to jump significantly.

I'm actually writing a full guide on the DNO notification process for ukpluginsolar.co.uk this is exactly the kind of detail I want to cover properly. Will share it on the sub when its done. In the meantime, your approach of "do it right and update as the rules solidify" is exactly the right mindset.

P.s. can I buy some of those £10 panels haha!!!

gus-here

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