DUoS Red, Amber and Green Bands: How They Differ by DNO Region, When They Reach the Bill, and What Load Shifting Is Worth

Distribution Use of System charges, or DUoS, are what your local network operator charges for moving electricity across the wires between the grid supply point and your meter. They are not a supplier margin and they are not negotiable. Each network operator publishes them in its charging statement, calculated under methodologies in the Distribution Connection and Use of System Agreement, and Ofgem governs them through its network charging work and the RIIO-ED2 price control.

For most low voltage and high voltage sites, DUoS arrives in several parts: a standing charge, a fixed residual charge based on the band your site sits in, a capacity charge per kVA per day if you are half-hourly metered, a reactive power charge, and time-banded unit rates. Those unit rates are the red, amber and green bands.

What the three bands are meant to do

The banded unit rates are a forward-looking signal. Network operators want to discourage consumption at the times when local demand is closest to the limits of the existing network, because that is what drives reinforcement spend. Red covers the tightest hours and amber the shoulder periods. Green picks up everything else: mainly nights, weekends and quiet daytime hours.

The gap between the bands is deliberately steep. In many charging statements the red rate is an order of magnitude above amber, and amber is a multiple of green, with green sometimes close to zero. That is the point of the design. A modest price difference would not move anyone's behaviour.

Two things follow. First, the bands only bite on consumption, so they do not touch your capacity charge or your fixed residual charge. Second, since the Targeted Charging Review moved network residual costs onto fixed bands, and triad avoidance for demand customers ended with it, red band avoidance is one of the few network charges left that a site can genuinely influence through timing.

Why the clock is different in every region

Fourteen distribution licence areas cover Great Britain, run by six network groups. Each publishes its own charging statement, and each sets its own band times. The variation is real and it catches people out.

Common ways the regions differ:

• Number of red windows. Some areas run a single weekday red period in the late afternoon and early evening. Others split red across a late morning peak and an evening peak.
• Start and end times. Red windows of 16:00 to 19:00 are typical, but neighbouring areas may run 16:30 to 19:30, or extend later in winter.
• Seasonality. In some areas red applies on weekdays all year. In others the winter months carry a red band and the summer equivalent hours drop to amber.
• Weekend and bank holiday treatment. Weekends are usually green or amber throughout. Many statements treat bank holidays as non-working days, so red does not apply, but that is a per-statement detail worth checking rather than assuming.
• Voltage and metering class. Band times and rates differ between low voltage and high voltage, and between half-hourly and non-half-hourly tariffs, within the same region.
• The size of the spread. Two sites in different regions can have identical red hours and very different red-to-green ratios, which changes the value of shifting the same kWh.

Larger sites connected at extra high voltage, and some HV sites, are charged under the extra high voltage methodology instead, where charges are site-specific and the simple red, amber and green framing does not apply in the same way. Ofgem's Access and Forward-Looking Charges Significant Code Review tidied up how forward-looking signals and residual charges sit alongside each other, but it did not remove the banded structure for mass-market metered supplies.

Charging statements are published ahead of the charging year, which runs from 1 April. Band times change less often than rates, though they do change, so a load-shifting plan built on last year's timetable can quietly stop working in April.

When bands show on the bill and when they are already priced in

Brokers need to get this part right at quotation stage, because it determines whether a client can act on any of it.

Fully fixed, all-inclusive contracts. Most non-half-hourly SME supplies are sold this way, at a single unit rate or a simple day and night split. The supplier has forecast the site's shape, applied assumed DUoS band costs, added risk premium, and blended the lot into the price. Move consumption from 17:00 to 22:00 and the bill does not change. The saving accrues to the supplier until the contract is repriced.

Fixed with pass-through. Wholesale energy is fixed; DUoS, transmission charges and levies are passed through at cost. The red, amber and green split usually appears as separate lines on the invoice, and shifting load produces a saving in the same month it happens.

Half-hourly flexible or fully pass-through. Standard for larger sites. Every element is visible, including capacity and reactive power, and the banded rates are applied to actual half-hourly volumes.

Where a client on an all-inclusive product wants to be paid for shifting load, the contract has to change first. That may mean moving to pass-through at renewal, or asking the supplier to reprice on a revised load shape. Suppliers will do the latter, but they price for the risk that the shape does not materialise.

What load shifting is actually worth

The arithmetic is simple. Annual saving equals kWh moved out of red, multiplied by the red rate minus the rate of the band you move into, multiplied by the number of chargeable days.

Work it through with your own statement. Take a site shifting 150 kWh out of the red window each weekday. With roughly 250 weekdays, that is 37,500 kWh a year. If the red rate is 10p/kWh and the green rate is 0.3p/kWh, the saving is around £3,640 a year. Halve the spread and the number halves. In a region with a narrower spread, or at a site that can only move 30 kWh a day, the same effort might return a few hundred pounds.

Some caveats apply. Load usually moves to amber rather than green, which cuts the spread. Shifting consumption to overnight hours changes your wholesale exposure too, sometimes favourably. If the shift involves running plant harder outside red, your kVA capacity charge and your metered maximum demand can move in the wrong direction. Half-hourly data quality also matters, because a shape built from estimates will overstate what sits in the red window.

Battery storage and on-site generation change the picture, since they can discharge through red without altering site operations, though the DUoS saving is only one revenue line in that business case.

One note on figures: rates and band times used above are illustrative. The only authoritative numbers are those in the current-year charging statement for the relevant distribution area, published by the network operator and approved under DCUSA governance overseen by Ofgem.

What to do next

• Pull the client's MPAN, identify the distribution area from the first two digits of the supply number, and download the current charging statement for that area rather than relying on a generic table.
• Check the contract type before promising any saving. If it is all-inclusive, the answer to "what will load shifting save us" is nothing until renewal.
• Take twelve months of half-hourly data, tag each period against the correct band, and calculate what is actually sitting in red. Many sites find the figure is smaller than expected.
• Model the move to amber, not to green, and net off any capacity charge consequence.
• Diary the April charging year change and re-run the numbers, since rates and occasionally band times move.
• Watch how half-hourly settlement reform affects non-half-hourly sites, as it increases the granularity suppliers work with: the MHHS Programme and Elexon publish current milestones.