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Competitive PricesHow the DNO measures maximum demand
If your site has a half-hourly meter (most do, especially above 100 kW peak), the meter records the kW average for every 30-minute period of the year — that’s 17,520 readings annually. The highest reading in any given month is that month’s maximum demand.
If your site has a maximum demand meter without HH (older installations), there’s a physical pointer that records the highest demand seen, and the meter is read monthly to capture it.
The number is not your highest instantaneous power draw — it’s the highest 30-minute average. A 5-second spike when motors start up doesn’t count. A sustained 30-minute high-load operation absolutely does.
Where MD shows up on your bill
- Capacity charge — usually billed in £ per kVA against either your maximum kVA or your agreed kVA, whichever is lower.
- Exceeded capacity charge — billed in £ per kVA against any portion of your maximum demand that exceeded your agreed capacity. Penalty rate — typically 1.5–3× the standard capacity charge.
- Unit rate uplift — for fully-fixed contracts, the supplier sometimes builds an MD assumption into the unit rate. A site that exceeds the assumed MD gets a worse renewal next time.
How much MD costs you
| Site peak demand | Typical monthly capacity charge | Annual |
|---|---|---|
| 50 kVA | £10–£25 | £120–£300 |
| 100 kVA | £20–£60 | £240–£720 |
| 200 kVA | £40–£120 | £480–£1,440 |
| 500 kVA | £100–£350 | £1,200–£4,200 |
| 1,000 kVA | £300–£800 | £3,600–£9,600 |
Indicative ranges. Actual rates vary by DNO region and tariff.
Four ways to lower maximum demand
1. Reschedule discretionary loads off peak. Walk through your half-hourly data and identify what’s running in the highest 30-minute period each month. Anything that could happen 4 hours earlier or later? Move it.
2. Sequence high-load machinery. If you have multiple pieces of equipment that can each pull tens of kW, stagger their start times. Two 30 kW chillers starting 5 minutes apart cost the same in energy but show up as 30 kW max demand instead of 60.
3. Add storage. Battery storage charges from the grid in low-demand periods and discharges during peaks. A 50 kWh / 30 kW battery system at a 200 kW site can shave 20–30 kW off recorded peak demand. CapEx £30–60k installed; payback 3–7 years on capacity charges, peak unit rates, and grid services revenue.
4. Demand-management software. Energy management systems can monitor real-time consumption and automatically throttle non-critical loads (HVAC setpoints, secondary refrigeration, EV chargers) when you’re approaching a defined kW threshold. Installed costs £2–10k depending on scale; works well alongside on-site solar or storage.
The interaction with kVA and load factor
Maximum demand, kVA, and load factor are three lenses on the same data:
- Maximum demand = your peak (a single point in time).
- kVA = the capacity the DNO holds open for you (a contracted level).
- Load factor = your average ÷ peak (a measure of how steady you are).
Lowering MD usually pushes load factor up at the same time — fewer extreme peaks means the ratio of average to peak gets healthier. Both effects compound: lower MD reduces capacity charges directly, and the resulting higher load factor improves your unit rate at renewal.
Working with Clearsight
On every HH-metered renewal we analyse maximum demand, agreed capacity, and load factor together — and flag specific actions where the data shows headroom. No upfront fees; we’re paid by the supplier you contract with.
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Related guides: kVA explained, What is load factor?, Half-hourly electricity meters, Business electricity pillar.