No rational response and notable exasperation that I should ask such questions – presumably because they didn’t know. I was trying to be prepared in case I had to suddenly deal with it.

Last week, I experienced a leaking air vent on top of the buffer cylinder. I asked if they had a part number. The number I was given was a purge/bleed screw, which looked like a small screw with a hole to allow air escape when loosened. I now realise the air vent was added by the installers but it fitted into a ½” boss, not something that would accommodate a bleed/purge screw.

Other instances around guarantee registration (website registration on the card didn’t exist/German address on the card) were met with indifference.

I compare this with very positive help from Worcester Bosch over ten years, including guiding me in sorting plumber’s bodged repairs.

For the brown gunge leak, they suggested limescale. It still beats me why that should emanate from around that valve. Similarly, the leaking air vent was, on examination, due to an accumulation of brown oily gunge blocking its exhaust. Any suggestions as to what it is are most welcome.

On 9 January 2026, Consumer Energy Solutions collapsed into administration. It ceased trading with immediate effect, made nearly 300 workers redundant (many of them in Wales, in communities where jobs are scarce) and abandoned thousands of households mid-installation. Solar panels generating electricity that could not be exported to the grid because nobody had signed off the paperwork. Air source heat pumps running without commissioning certificates. Pensioners in ill health left to find someone to finish work that CES had started, often months earlier, under a government scheme supposedly designed to protect them.

What has not been adequately scrutinised is what happened in the twenty-one months before CES went under, and whether the body charged with certifying that its work was safe and compliant did anything like enough to stop it.

Renewable Heating Hub, which engages with thousands of homeowners through its forums, emails and private messages, has documented more failed heat pump installations in 2025 than in any previous year. CES was the largest single contributor to that pattern. We contacted MCS directly and put five questions on the record. What follows is an account of what MCS said... and what it did not.

The day the certification died

On 29 March 2024, Consumer Energy Solutions supposedly lost its MCS certification. Its certification body removed it, following complaints about the technical compliance of CES installations. It was, by any measure, a significant event: one of the largest ECO4 contractors in the country had been found non-compliant and stripped of the accreditation that entitled it to access public money.

Nobody was told.

Renewable Heating Hub asked MCS directly: why was no public announcement made, and why were customers not notified? MCS replied that it was "not standard practice" to announce when a business loses its certification, adding that it was "unable to issue direct communications or offer direct support to consumers at the point in question" because, under the version of the scheme then in operation, MCS did not hold customer details at all.

Let that settle for a moment. The Microgeneration Certification Scheme, the body that for years has presented itself as the gold standard of consumer protection in the renewables sector, the gatekeeper to billions of pounds of public money, did not know who lived in the homes whose installations it was certifying.

It held no names. No contact details. No record of whose boiler had been replaced, whose loft had been packed with insulation, whose brand new heat pump was already struggling to heat the house. MCS does not audit or certify installers directly (that job is outsourced to certification bodies) and the quality of those audits has been inconsistent at best. When one of those installers fell over, MCS had no mechanism to reach the people most affected, because it had never thought to keep a list of them.

This is not a procedural technicality. It is a foundational failure of consumer protection, hiding in plain sight beneath a decade's worth of reassuring branding.

Two months of silence, then a reinstatement

MCS says it first became directly aware of consumer complaints against CES in May 2024, two months after the certification had already been removed. At that point, MCS suspended CES's sub-licence agreement and called a disciplinary hearing. Conditions were set. CES said it had met them. In June 2024 (less than three months after its certification was pulled) CES was reinstated.

When Renewable Heating Hub asked what steps MCS had taken to review post-March 2024 installations, MCS confirmed it had conducted 186 site audits of CES installations and held monthly oversight meetings from July 2024 onwards.

One hundred and eighty-six audits, against a company that in the year to January 2024 reported turnover of £81 million. CES reported pre-tax profits of approximately £35 million with growth that appears to have been almost entirely ECO-funded. A company of that scale and that output, covering heat pumps, solar PV, insulation and more across the length and breadth of the country, was subject to 186 audits over the course of enhanced monitoring. The inadequacy of that figure barely requires comment.

Asked whether Ofgem, TrustMark, energy suppliers or Retrofit Coordinators were informed of the March 2024 revocation, MCS was careful with its language. The initial suspension, it said, was a decision made by the certification body, not by MCS.

MCS only notified external stakeholders, including TrustMark, when it made its own decision to suspend CES's sub-licence in May 2024. In other words, for the two months between March and May 2024, a company that had lost its certification was continuing to operate while the watchdog charged with oversight of the wider scheme was not yet formally in the loop.

The question MCS refused to answer

Renewable Heating Hub asked MCS how many installers in total lost their certification between January 2024 and January 2026, and crucially, how many of those continued delivering ECO4 work. It is one of the most important questions in this entire affair, because the answer would tell us whether the CES situation was an isolated case or a symptom of something far more systemic.

MCS did not provide a number. Instead, it offered a generalised explanation of why certification status can change frequently, noting that losses often reflect administrative issues rather than performance failures. It noted that decertified businesses cannot legally access ECO4 funding. What it did not do was tell us how many companies lost certification, how rigorously that bar was enforced in practice or whether CES was unique in regaining certification and continuing to operate. That evasion is itself informative.

What ECO4 actually did to vulnerable households

Analysts believe between 60,000 and 70,000 homes suffered serious near-term or latent defects during the four-year term of ECO4. Of the approximately 40,000 air source heat pumps installed, many are believed to be inappropriate or poorly designed, yet the warranties underwriting those installations last just two years. The government did not complete a full fraud risk assessment before ECO4 was implemented in 2022, and it failed to understand the scheme's exposure to fraud from the outset. 

The forums at Renewable Heating Hub have documented case after case: homeowners who were awarded ECO4 grants and found themselves worse off, with electricity bills that had skyrocketed, systems they didn't understand and no aftercare to speak of. Complaints processes routinely drag on for years... some cases on the Renewable Heating Hub forums have now run for four or even five years without resolution, with homeowners passed from MCS to RECC or HIES to installers to certification bodies in an endless cycle of finger-pointing and deflection.

This is not a side effect. It is the direct consequence of a system in which accountability was diffused so thoroughly across so many bodies that it effectively belonged to none of them. No single organisation had overall responsibility for preventing and detecting fraud on ECO4 and GBIS, the Public Accounts Committee concluded. MCS is funded largely by installer levies and as one industry observer has noted, he who pays the piper calls the tune. Whether or not that explains MCS's chronic reluctance to act decisively against CES, it is a question that deserves a straight answer.

The reforms that arrive too late

MCS's response to Renewable Heating Hub's fifth question, what changes has it implemented in light of the CES case, runs to several hundred words. The reforms outlined are, on paper, substantive. MCS will now manage complaints centrally. It will contact every recipient of a certified installation to assess satisfaction. Financial protection products will provide at least six years of cover, with a capped excess of £250. Pre-certification checks will include a business's financial health and legal history. Installers will have a direct, formalised relationship with MCS for the first time.

The transition deadline for the redeveloped scheme is 31 March 2027.

Read that again. The body that presided over the MCS certification and subsequent reinstatement of Consumer Energy Solutions (a company that went into administration in January 2026) has set itself a deadline of March 2027 to complete the reforms that would have prevented it.

MCS has had over a decade to get this right. In that time, it has presided over one of the most fragmented, inconsistent and opaque certification systems in the UK, with its response to legitimate criticism characterised by platitudes about "raising standards" and "protecting consumers" that ring hollow in practice. 

The reforms are what MCS should have built years ago. That they are only arriving now, after the collapse of one of the UK's largest ECO4 contractors, after thousands of vulnerable families were left with inadequate heating, after the Serious Fraud Office launched a £44 million investigation into the wider scheme, is not a vindication of the regulator. The Serious Fraud Office's investigation centres on allegations that public funds were obtained through fraudulent submissions for energy efficiency work that was either never carried out or only partially completed. 

MCS did not create ECO4. It did not set the scheme's funding rules or determine which installers would benefit. But it was the scheme's standard-bearer... the organisation whose certified mark was supposed to tell consumers that the work being done in their homes was safe, properly designed and independently verified. In the case of Consumer Energy Solutions, that promise was made and then quietly unmade on 29 March 2024, with no announcement, no notification and no mechanism for the people most affected to even find out what had happened.

The regulator that failed them is now promising to do better. Those promises deserve scrutiny, not applause.

Just a quick one...

I have a two zone system - daft really as we're in a bungalow & the second zone is just the two bedrooms. I've replaced the stupid neomitis thermostat in zone one with an old Hive one - mainly so I can control & monitor things. What's the easiest way to make it just one zone? I have motorised valves for both zones. 

I had thought of just connecting the two "demand"s together?

Steve

The piece of the jigsaw that my 75 year old brain is struggling with is this - ‘what function does the set temperature in the App have in the above set up’? It is currently set at 19C with an actual room temp of 19.8C.

It was badly done and I now plan to improve the pipework by putting the volumiser in the CH flow and reducing the number of multiplex elbows, all with the objective of improving flow.

The towns water feed to pressurise the system is still as original, i.e. to the middle of the buffer/ volumiser tank, (as diagram below) but I am uncertain if this is still the best point for the towns water pressurisation.

The DHW flow is from the 3 way valve and its return taps into the main return to the Ecodan.

Comments would be appreciated.

There is a curious tension at the heart of Britain’s energy transition. On paper, the direction of travel is unequivocal: electrify heat, electrify transport, expand distributed generation and let households become active participants in a cleaner, more flexible grid. In practice, however, that ambition is increasingly encountering friction, not in the technology, nor even in consumer appetite, but in the infrastructure and governance that sit beneath it.

We have felt this tension directly. Our own system is, by most standards, unremarkable for a household leaning into electrification: a 6kW solar PV array, paired with a 6kW inverter and an 18kW air source heat pump. All of it approved under G99.

And yet, the moment we attempted to take the next logical step (adding 20kWh of battery storage) we found ourselves back at the starting line. The battery system comes with its own 3.6kW inverter. That seemingly modest addition triggers a fresh G99 application, which is fair enough. Our installer has submitted it, but his expectation is blunt: rejection is likely.

This is not an isolated anecdote. Across the country, installers are reporting a growing number of refusals from Distribution Network Operators (DNOs). The reasons vary in their technical framing (harmonics, fault level constraints, thermal limits, voltage rise) but the underlying message is consistent. The network, at least in its current configuration, is not always willing to accommodate the decentralised, electrified future it is being asked to host.

Harmonics, in particular, have become a recurrent justification. In simple terms, these are distortions in the electrical waveform caused by non-linear loads and inverters. Too much distortion, and sensitive equipment can malfunction; too little control, and system stability can be compromised. It is a legitimate concern. Modern grids are increasingly populated by inverter-based technologies (solar PV, batteries, EV chargers) and their cumulative impact is not trivial. But the invocation of harmonics as a reason for refusal is often opaque to the homeowner. It arrives as a technical verdict with little practical recourse.

Voltage rise is another frequent constraint. When households export electricity (particularly in rural or lightly loaded networks) the local voltage can exceed statutory limits. The more generation connected to a given feeder, the greater the risk. Thermal constraints follow a similar logic: cables and transformers have finite capacity, and sustained high export or import can push them beyond safe operating limits. Fault levels, meanwhile, relate to the maximum current that can flow during a short circuit. Add enough generation, and those limits can be breached, requiring costly reinforcement.

None of this is unreasonable in isolation. Grid stability is not a theoretical concern... it is the foundation upon which the entire system rests. The DNOs are, quite rightly, cautious. They are custodians of infrastructure that was never designed for millions of small generators pushing power back upstream. Their challenge is structural as much as operational.

The difficulty arises when that caution begins to collide with national policy. The UK is actively encouraging households to install heat pumps, to adopt electric vehicles, to generate their own electricity and to store it. Each of these moves increases reliance on electricity, while also offering flexibility that could, in theory, support the grid. Batteries, for instance, are not merely passive assets. Properly integrated, they can absorb excess generation, reduce peak demand and provide ancillary services. They are part of the solution.

And yet, at the point of connection, they are often treated as part of the problem.

Consider a more typical British home. A semi-detached property installs a 4kW solar array under the simplified G98 process... no prior approval required, provided export is limited. Encouraged by rising energy prices, the homeowner then adds a 5kWh battery with a hybrid inverter. That upgrade may still fall within permissible limits, depending on configuration. But the moment they consider expanding, perhaps adding a second battery, or upgrading the inverter to enable higher discharge rates, they can find themselves pushed into G99 territory. The process becomes slower, more complex and increasingly uncertain.

Or take a household installing a heat pump. Electrification of heat significantly increases peak demand, particularly on cold winter evenings. Add an EV charger into the mix, and the load profile becomes even more pronounced. In theory, a battery could mitigate that demand, charging during off-peak periods and discharging when needed. In practice, the very addition of that battery may be constrained by the network’s perceived limitations.

There is a structural paradox here. The technologies that could alleviate grid stress are, in some cases, being constrained by the grid itself.

G100, which allows for export limitation devices to cap the amount of electricity fed back into the network, was meant to offer a workaround. By ensuring that export never exceeds a predefined threshold, it provides DNOs with a degree of certainty. Yet even G100 applications are, increasingly, subject to scrutiny and, in some cases, rejection. The reasons again return to system integrity: concerns about compliance, enforcement and the cumulative effect of many such systems operating simultaneously.

The result is a growing disconnect between policy ambition and operational reality. Households are being told to electrify, but not always being given a clear or reliable pathway to do so. Installers are navigating an increasingly complex landscape of applications, assessments, and conditional approvals. And the DNOs, for their part, are managing a system under strain, with limited visibility of what is coming next.

It is worth asking whether the current framework is fit for purpose. G99 was designed in a different era, when distributed generation was a niche rather than a norm. Its processes, while robust, are not always aligned with the speed and scale of the transition now underway. The question is not whether standards should be relaxed (grid stability cannot be compromised) but whether they can be modernised.

There are models elsewhere that hint at a different approach. More dynamic connection agreements, for instance, could allow assets to operate within flexible limits, responding in real time to network conditions. Greater standardisation of inverter behaviour (particularly around harmonics and voltage support) could reduce uncertainty. Enhanced data sharing between households, aggregators and network operators could improve forecasting and planning.

But these are not trivial reforms. They require coordination, investment and a willingness to rethink long-standing assumptions about how the grid operates.

In the meantime, households are left navigating a system that can feel inconsistent. One application sails through, another, seemingly identical, is refused. One DNO takes a pragmatic view, another applies a stricter interpretation. For the average homeowner, the experience is not one of a coherent national strategy, but of a postcode lottery.

There is also a broader economic question. Electrification is not just a technical transition, it is a financial one. Households are being asked to invest significant sums in new technologies (heat pumps, batteries, EVs) often with the promise of long-term savings and environmental benefit. When those investments are delayed or derailed by connection issues, confidence is eroded. The risk is not merely individual frustration, but a slowing of adoption at precisely the moment it needs to accelerate.

None of this is to suggest that the DNOs are acting unreasonably. On the contrary, their caution reflects the seriousness of their mandate. But the system as a whole appears misaligned. Policy is pulling in one direction... infrastructure and regulation are, at times, resisting.

The deeper question is whether Britain is attempting to run a 21st-century energy transition on a 20th-century grid architecture. If so, the friction we are seeing is not an anomaly, but an inevitability.

For now, our own battery application sits in that uncertain space between ambition and approval. It may be accepted, perhaps with conditions. It may be refused. Either outcome will be instructive. But the broader issue will remain. Electrification, in principle, is straightforward. In practice, it is mediated by a network that must evolve as quickly as the technologies it is being asked to support.

Until that alignment is achieved, the path to a fully electrified Britain will remain, in subtle but significant ways, constrained not by what households are willing to do, but by what the grid is prepared to allow.

In March 2024, we had an F2050-6 and SMO S40 installed - an ideal match on paper for a heat loss of 4.92kW @ -2.4 °C.

May 2024 saw temperatures rise enough to trigger cooling mode. Shortly after starting, the system would stop with a “Low LP cooling operation” alarm. My installer spoke to NIBE and advised that “we just need to adjust one of the settings in the cooling menu”. Settings changes didn’t work - the same alarm would continue to be raised frequently throughout the summer. I’ll come back to this later on…

Temperatures dropped in December, and the system began to struggle. Below ~3 °C outside it would defrost every 35 minutes, and would barely reach the target supply temperature (40 °C at -2.4 °C) before another defrost was triggered. Eventually, this triggers an emergency mode, which turns on the DHW immersion. This defrosting spiral would continue until the outdoor temperature increased. NIBE Homeowner Care agreed that defrosting this frequently was not normal.

Most of December and January was spent chasing Homeowner Care and my installer for some action. Eventually, it was agreed that NIBE would send an engineer to check the refrigerant charge.

The NIBE engineer visited in February 2025, and found the outdoor unit had 900 g of R32 instead of the 1,300 g specification. A leak must have been ruled out as the engineer recharged the unit to the correct specification. In the following days, the system continued to struggle, so NIBE concluded that the unit may be undersized, and there was nothing more they could do.

After arguing that running for nearly a year with a significant refrigerant deficit may have caused internal damage, NIBE eventually offered a replacement unit. To their credit, they offered an upgrade to the F2050-10, which they promised would ensure the outdoor unit was "both large enough and definitely not faulty".

The F2050-10 was installed in March 2025 and seemed to be working well until December 2025 when firmware version 4.7.5 was released. A few days after applying the update, I noticed repeated pressure/discharge spikes:

Homeowner Care seemed concerned by the high readings and agreed I should downgrade the firmware back to 4.6.4. A later update to 4.7.6 in January caused the same behaviour. Later in the month, I noticed what seemed to be abnormal banding on the evaporator. This photo was taken 9 minutes before a defrost at 3℃ outside:

I asked my installer to escalate to NIBE, who commissioned an independent specialist to investigate. In February 2026, they recovered and weighed the gas from the F2050-10 and found it was undercharged by 290g (1,550g recovered vs 1,840g spec). An overnight nitrogen test confirmed there were no leaks, so the unit was charged to the factory specification. NIBE Customer Care subsequently stated that the unit is “operating as intended”. However, after being correctly charged, the system still appears to be unstable, with frequent high pressure and discharge spikes:

While on site, the engineer asked me if there had been any system alarms - none from the F2050-10, but I mentioned the F2050-6 had triggered “low LP cooling operation” many times. He advised this was a sign of low refrigerant, so the fault with the original unit could have been picked up in May 2024.

I was shocked that a second unit had been confirmed to be undercharged with refrigerant. The nameplate charge level is a fixed engineering specification that is critical to the performance, efficiency, and longevity of the product.

Conscious of my experience with the first unit, I chose to exercise my final right to reject the system with my installer. NIBE quickly offered a third F2050, which I declined due to a total loss of confidence in the product. They subsequently offered a future “F2060” without any further information or timeline for installation. The F2060 doesn’t appear to exist in any UK literature or the MCS database.

It’s over two years since our original installation, and I’m yet to receive the premium heat pump “manufactured in Sweden to the very highest standard” that I paid for. I have two engineers’ reports that document latent defects in both the supplied units.

One faulty unit could be considered bad luck, but two…?

Little story of battery woe, and then an appeal for any help/info/hope people might be able to offer. 

The Story:

We moved into our home in Dec 2022.

In March/April 2023 we had the following installed:

- 6 solar panels (3.27kWp) and

- Pure Drive 10kW AC coupled battery installed (gateway AC connection), with

- Solis inverter (S6-GR13PK, inverter topology is non-isolated).

Small local installer.

We told the installer that we wanted a system that worked off grid, and would re-charge from solar in the event of a power outage. We're pretty rural, and we knew that when storm Arwen came it took this area out for two weeks. I was pretty 'green' to renewable energy and didn't understand the specs we were given by the installer. My bad. Had I understood the specs, I would have understood that the system would not do what we wanted. In my defence, I had a phone call with the installer and specifically asked if it worked off grid, and was told it did. The written specs (had I understood them) told a different story.

It was installed, and in August that year there was a power cut and (imagine my surprise!) it didn't work off grid. I queried it. I then spent 10 months chasing and chasing and getting no where (there were actual tears) before being told by the installer "We're busy doing commercial work not residential." I got the message. I spoke to Pure Drive, and they put me onto two other approved installers in the area who could look at it. One came out. Explained that based on what I'd said I wanted, I'd been sold a dud set up. Absolutely gutted, because we'd spent £15k on the system in total (panels and battery plus install).

That second installer agreed to do a 'work-around' for us whereby there is a back-up circuit installed in the house that has sockets (they're all on one circuit) and lights, and not the kitchen. In a power cut, we get the heating still working, sockets (so fridge freezer is OK) and lights. We can use what's in the battery at the time, but it doesn't have capacity to re-charge from solar. I was told there's no way to get that capability without replacing both the battery and inverter, which we can't afford.

I queried this with Pure Drive, wondering if I could replace the inverter with a hybrid inverter, but alas no. The same answer: I'd have to take everything out, and start from scratch.

There have been a couple of other niggles.

- Most mornings the battery trips out when the sun comes up, and we have to flip it back on at it's fuse board. No idea why. If we miss that, it's just out until we notice.

- Intermittently but at multiple occasions in the day the Solis inverter presents a 'NO GRID' error, mostly when it's sunny. The upshot of about 2.5 months of query, chase, and investigation regarding that with the original installer, second installer, Pure Drive, Northern Powergrid, and Solis is that the panels and/or battery are 'overloading' the Solis inverter in sunny periods and it shuts itself off to protect itself, and then turns back on again. It also turns out that the Solis inverter wasn't installed with remote monitoring, and my original installer agreed to install the required piece of kit so that it could be remotely monitored, and then didn't. All in all, I gave up pursuing that further because it doesn't seem to massively effect performance - the inverter switches off for 30secs to 1min30secs at a time, during sunny periods, multiple times a day, but, it comes back on again and the battery can then get back to charging.

Apart from that it, it does charge, store, and power the house as it should. I have it to charge at night, and have it in 'power cut' mode so if the worst happens we should at least have a decent amount of charge in the battery to keep things ticking over. 

The Question:

Is there any way - any at all - that I can affordably (I'm thinking £2k-ish...?) get this system to work as I originally wanted it to: panels and battery, optimising home usage, and in the event of a power cut to have the ability to charge up the battery from the panels and run the (low-power) essentials of the house from the battery, off grid.

So far I haven't found it, so I'm not hopeful. I last looked into this maybe over a year ago (early 2025) and it was gruelling trying to get answers - that's partly down to me not really understanding the tech (again, my bad).

I know this is very technical and no one can see my set up, so there's maybe a limited amount anyone can say - I think I'd even just appreciate some commiseration at this point.

I've wondered about selling the equipment, and using that to fund the correct kit/installation, but I expect we wouldn't get close to covering the cost from the second hand market.

As I say any advice about options or ways forward very welcome, and thanks in advance for anyone willing to read my tale of woe and even consider replying. 

Is this likely to be a real situation or is it something to do with the latency in the data logger?

Examples: