The 99% Charger: Reliability Is Now a Data and Operations Problem
A 99% network average is a poor predictor of whether the charger in front of you works. Reliability is now a whole-stack operations discipline.
For years, the defining question about UK public charging was coverage — how many chargers, how fast, how widely spread. That question isn't answered, but it's no longer the only one that matters. With over 121,000 public chargers live by June 2026 and ultra-rapid infrastructure growing particularly quickly, the network is large enough that its biggest failure mode has shifted from "not enough chargers" to "chargers that don't work when a driver needs them."
UK regulation now requires an annual 99% average reliability level across rapid networks, alongside open OCPI data, pricing transparency, contactless payment and a staffed helpline. That's a meaningful statutory floor — and also a number that's easy to misread as a guarantee of a good experience at any single site, on any single day.
This briefing sets out what the reliability measure actually covers, what it can obscure, and what the operations behind a genuinely reliable network look like.
Scale, by the numbers
What the 99% measure includes — and conceals
The statutory measure is a network average, calculated across a rapid charging operator's entire estate over a reporting period. That's a genuinely useful accountability tool at industry level — and a poor predictor of whether the one charger a driver is standing in front of, right now, will actually work. A network can hit 99% overall while a specific site, in a specific location, sits meaningfully below that average for weeks at a time.
It's also worth knowing that downtime isn't only a hardware failure. A payment-terminal fault or a communications failure back to the CPO's platform can count as charge-point downtime under the reporting rules, even when the charger's power electronics are working perfectly.
What actually causes downtime
Figure 1. A charger that "won't work" is a symptom, not a diagnosis — the fix depends entirely on which of these four systems actually failed.
Remote monitoring, alarms and field maintenance
Reliability at this scale is a logistics operation as much as an engineering one — remote monitoring that flags a fault before a driver reports it, alarm thresholds tuned to catch degradation early rather than only outright failure, and a spares and field-technician network dense enough to actually reach a faulted site within a commercially credible window. A charger that's monitored well but takes two weeks to physically fix still fails the driver who needed it today.
Communications resilience and data accuracy
A charger that loses its connection to the CPO's back office can often keep charging locally — but it will also stop reporting accurate status through OCPI, which means the live map a driver is checking may show it as available, or as faulted, when neither is quite true. Keeping OCPI status data accurate isn't a cosmetic concern; it's directly what stands between a driver and a wasted trip to a site that turns out not to work.
SLAs that span the whole stack
Charger hardware SLA
Manufacturer commitments on fault rates and spares availability, not just headline uptime claims.
Payment SLA
The terminal provider's own uptime commitment, tracked separately from the charger's.
Telecoms SLA
Connectivity resilience for the comms path back to the CPO platform, including a fallback bearer.
Software SLA
Back-office platform availability and status-data accuracy, measured and reported independently.
2025 is the first full year of statutory reliability reporting, which means the industry is only now getting a real baseline to work from. The operators who treat reliability as a whole-stack operations discipline — not just a headline percentage — are the ones who'll be ahead of that reporting, not caught out by it.
How a read moves across the estate
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Chris Gales
Chris Gales leads CEHG. He converts complex technical and commercial choices into clear decisions and dependable outcomes for utilities running connected device estates at scale.
He writes these field notes from the practice — on bearer migration, smart metering architecture, procurement and operations — to help estates start counting down early.