Reactive power charges for businesses need checking against the individual electricity supply, not just the fact that it is moving to half-hourly settlement. A new charge is a reason to request the tariff and meter data before approving electrical work or buying correction equipment.
For a factory, holiday park or larger commercial site in Cornwall, the useful starting point is straightforward: establish whether the charge applies, check how it was calculated, then decide whether the installation needs assessment.
Why half-hourly settlement does not automatically create a charge
Market-wide Half-Hourly Settlement (MHHS) is changing how electricity consumption is settled. However, half-hourly settlement for business electricity does not automatically create a separate reactive-power charge.
The programme's supplier-readiness milestone, M14, was approved in October 2026. That did not mean every customer's migration was complete. Ask the supplier to confirm the position for your supply rather than inferring it from programme announcements.
Start with the Meter Point Administration Number (MPAN), which identifies the supply. Check the network tariff, supply contract and any transitional protection for that MPAN. Several supplies at one site may not all have the same charging position.
Keep active and reactive energy separate
Active energy is recorded in kilowatt-hours (kWh); reactive energy is recorded in kilovolt-ampere reactive hours (kVArh). Power factor describes the relationship between active and apparent power. A reactive-energy charge is not simply another price per kWh.
When NGED South West reactive power charges apply
The relevant local reference is National Grid Electricity Distribution's South West charging statement for 2026/27, effective from 1 April 2026. Its excess reactive-power provisions cover specified low-voltage (LV) and high-voltage (HV) site-specific demand MPANs.
The test applies separately to each half-hour. Reactive energy above 33% of active energy is chargeable at the applicable tariff rate. The statement describes this as equivalent to an average power factor of 0.95. Only the excess above the threshold is charged.
For illustration, 100 kWh of active energy in an applicable half-hour gives a threshold of 33 kVArh. If reactive energy were 45 kVArh, the excess would be 12 kVArh. That is not a whole-month calculation.
Two qualifications matter. For properties under P432 or MHHS transitional protection, the statement specifies fixed and unit distribution charges only. If the tariff is EDCM, the statement provides no separate reactive-power component, although those charges reflect power factor.
A power factor of 0.95 is therefore not a universal legal requirement for commercial premises. These are specific charging provisions. Do not apply them unchanged to every Cornwall connection, particularly where a private or independent network is involved.
The bill and meter records to request first
Before comparing equipment quotes, ask your supplier for:
- The MPAN, exact charge description and billing dates.
- The network tariff code, charged kVArh and rate used.
- Confirmation of whether transitional protection applies for that billing period.
- Matching half-hourly active and reactive energy readings, with units identified.
- Dates when the metering, settlement status or tariff changed.
- The contract terms explaining how network charges are passed through.
EDF, for example, describes reactive-power charges as network charges passed through for a supply point and says its customers can view reactive power in a report of half-hourly meter readings. Other suppliers' bill layouts and data access arrangements may differ.
Keep the invoice and interval data for the same MPAN and dates together. A monthly total or single power-factor figure cannot show which half-hours exceeded this threshold.
Ask the supplier to show how the billed quantity was calculated, rather than simply saying the site has a low power factor. If the invoice and records do not match, ask for the discrepancy to be explained before commissioning equipment.
If a charge appears after a contract renewal or metering change, check the billed dates and the terms that changed. The timing may help frame the query, but it does not prove that the installation has deteriorated or needs correction equipment.
If you are checking before migration
Ask the supplier which tariff and protection arrangements are expected to apply to your MPAN, from what date, and whether suitable interval data is available to assess the likely exposure. Do not budget for a universal reactive charge just because the supply is moving to half-hourly settlement.
When commercial power factor correction is worth assessing
An electrical assessment becomes useful once the charging position is understood and there is a measured pattern worth investigating. The question is whether the site's operating profile and tariff justify considering commercial power factor correction, not simply whether someone quotes a target figure.
The IET's technical Q&A advises measuring power-factor variation over an operating period rather than relying on a snapshot. A seasonal or variable-load business should explain when equipment runs and which operating periods its readings cover.
It also notes that capacitor banks can create harmonic resonance. Correction therefore needs competent, site-specific assessment; it is not an automatic purchase whenever a bill mentions reactive power.
Compare a proposal with the actual excess charges, equipment costs and expected operating pattern, not the whole electricity bill. Ask for its measurement basis and assumptions. Do not assume correction will reduce kWh use, guarantee bill savings or achieve a standard payback period.
If you are planning a commercial electrical fit-out, include the billing evidence in the brief and identify changes to equipment or operating hours. Today's readings may not represent the future site.
Who should deal with each part of the query
Keep billing verification separate from electrical diagnosis:
- Supplier: confirm the charge, contractual pass-through, tariff and any transitional protection.
- Meter or data provider: clarify access to relevant half-hourly records and any data issues, often through the supplier.
- Distribution network operator (DNO): clarify the network charging basis where necessary, with the supplier involved.
- Electrical contractor: assess the installation and operating profile when the evidence supports a site-side investigation.
Give the parties handling the query the same MPAN, billing period and interval dataset. That helps prevent a supplier query about one supply becoming an electrical investigation of another meter point. Agree who is responsible for the next action before commissioning work.
Discuss the site-side electrical work
Call Maenporth Electrical on 01326 250297 to discuss our commercial electrical services. Based at Maenporth, we serve Falmouth, Penryn and wider Cornwall. Have your bill, MPAN and available interval readings ready so the next step can be scoped around your site.