ENA EREC G5 · P28 · G99 · G98 · P29
UK power-compliance tools and guidance, for engineers.
Calculators and clear guides for the ENA Engineering Recommendations that govern connections to UK distribution networks. Written by the engineers who use them.
The P28 calculator is free and needs no account to use. Sign up free to save your studies and download PDF reports.
P28 Calculator
Step voltage change, Stage 1 eligibility, RVC category and the Pst = 0.5 flicker characteristic — four checks from one set of inputs, each citing the clause it comes from.
Run a checkG5/5 Calculator
Stages 1, 2 and 2C harmonic compliance with audit-grade PDF reporting. Used by consulting engineers and DNO applicants across the UK.
Open the calculatorQuick P28 check, free
For anyone assessing a motor, EV charger, heat pump or general load against ENA EREC P28 Issue 2 (2019). Get the step voltage change, whether Stage 1 applies, which RVC category you fall in, and whether the flicker characteristic is met — with the working shown.
Open the P28 calculatorFull G5/5 harmonic assessment
Where P28 covers voltage fluctuation, ENA EREC G5 Issue 5 (2020) covers harmonic distortion. Our G5/5 calculator takes you through Stages 1, 2 and 2C and produces the report you submit to the DNO.
What G5/5 requiresStandards, in plain English
What each Engineering Recommendation actually requires, who it applies to, and how to apply it — with clause references throughout, so you can check us against the source.
Read the guidesTwo standards, one connection
Most connections need both assessments
P28 and G5 answer different questions about the same connection. P28 asks whether your equipment will make the voltage move — dips when it switches on, flicker when it cycles. G5 asks whether it will distort the waveform. A DNO application usually needs both.
Start with P28
It is free, takes a minute, and tells you immediately whether the voltage side of your connection is straightforward or needs a proper study.
Then the harmonic side
If your P28 result comes back needing a Stage 2 assessment, the harmonic side almost certainly needs one too. The G5/5 calculator handles it end to end.
Guides
Standards explained properly
No fluff, no hedging, clause references throughout. Written for engineers who need to apply the standard, not skim a summary of it.
What is ENA EREC P28?
What the standard covers, what it deliberately does not, who has to comply, and how the three-stage assessment fits together.
Read P28P28 Stages 1, 2 and 3 explained
Which stage applies to your connection, what each one actually requires, and what happens when equipment does not qualify for the simplified route.
Read ReferenceEREC P28 at a glance
The limits, the tables and the equations in one place — planning levels, RVC categories, generic supply impedances and the Stage 1 thresholds.
Open the referenceWho builds this
Built by engineers who use these standards
Pendulum Power Consultants Ltd is a UK power-systems consultancy. We built the G5/5 calculator because we needed it ourselves, then put it through a full compliance verification so it could be relied on in DNO submissions. The P28 calculator is built to the same standard, and it is free.
Every number our tools produce cites the clause it comes from, and every assumption we make where a standard is silent is labelled as ours rather than the standard's.
Standards referenced
ENA EREC G5 Issue 5 (2020)
ENA EREC P28 Issue 2 (2019)
Get started
Check your connection against P28 in about a minute
No account needed to run a check and see the full working. Create a free account when you want to save studies and download PDF reports.