DUoS Charges Explained: The Hidden Network Cost With a Traffic-Light Price Tag

What DUoS charges are, in plain words

DUoS is short for Distribution Use of System. It is the rent your regional distribution network operator (DNO) charges for using the local wires, the lower-voltage cables and substations that carry power the last leg to your meter. Think of it as a toll for the local roads, separate from the cost of the electricity travelling on them. Your supplier pays this toll to the DNO and adds it to your bill.

If you run a household, you will never see "DUoS charges" written down: it is folded silently into your unit rate and standing charge. If you run a business with a half-hourly meter, you often see it broken out, and that is where it gets interesting, because DUoS does not cost the same all day.

The red, amber and green DUoS bands

DUoS unit rates change with the time of day, using a traffic-light system. The idea is simple: power is most expensive to deliver when everyone wants it at once, so the charge is highest then and lowest when the network is quiet.

The exact band times and rates are set by each DNO and published every year in its charging statement, so they differ by region. A red-band kWh can cost many times what the same kWh costs in the green band, which is the whole point of the design.

See what moving everyday loads to off-peak could save

The saving is not about using less, it is about when. Some appliances can run overnight instead of at peak time, the dishwasher, the washing machine, the car charger. Tick the ones you could shift and the tool adds up the rough yearly saving, using the gap between peak and off-peak prices. The same idea drives DUoS for businesses and a time-of-use tariff for homes.

Averages based on Energy Saving Trust appliance figures; EV charging assumes about 20 miles a day at roughly 3.5 miles per kWh. Rates are pulled live from our UK tariff feed: the cheapest standard rate is 23.9p and the cheapest off-peak night rate is 6.5p per kWh, a 17.4p gap. Worked example: moving the washing machine and dishwasher (~8 kWh a week, about 416 kWh a year) to off-peak saves roughly £72 a year at that gap; adding overnight EV charging takes the shift to roughly 2,500 kWh a year.

The belief that costs businesses money: "we just pay what we use"

Most bill-payers assume the network charge is a flat cost they cannot influence, the same per unit whenever they switch the lights on. For households that is effectively true, because DUoS is averaged and hidden. But for a business on half-hourly metering it is the opposite: the same kilowatt-hour costs wildly different amounts depending on the clock. Treating DUoS as fixed means leaving money on the table every single weekday evening.

Why most explanations get DUoS wrong

Typical guides define DUoS as "a charge for using the distribution network" and stop. That misses the only two things that matter for your money: first, that the charge is a time-of-day price signal you can respond to, and second, that the band times and rates are regional, so a national average is useless for planning. An explanation that does not point you to your own DNO charging statement has not actually helped you.

DUoS vs TNUoS, and where they sit among non-commodity costs

It helps to see the family. Your bill divides into the commodity (the energy itself) and non-commodity costs (everything else). Inside non-commodity costs sit the two network charges: DUoS for the local distribution network and TNUoS (Transmission Network Use of System) for the high-voltage national grid, alongside policy levies and balancing costs.

For most users DUoS is the larger of the two network charges, and crucially it is the only one with the red/amber/green structure you can act on. TNUoS is charged differently (largely on your demand at system peak), so it rewards a different behaviour. Lumping them together as "network costs" hides the fact that DUoS is the one most businesses can practically reduce.

The insider insight: the red band is a signal, not a penalty

Here is the part the industry rarely spells out for customers. The red band is not the DNO being greedy at peak time. It is a deliberate price signal: making peak power expensive is meant to nudge large users to spread demand, so the network needs less reinforcement and everyone pays less to build it. The customers who understand this treat the red band as an instruction, "move what you can", rather than an unavoidable cost.

The 30-minute win most businesses miss Because DUoS is settled in half-hourly periods, a process that starts just before the red band ends, or finishes just after it begins, can sometimes be nudged 30 minutes to land entirely in amber or green. No production is lost, no kilowatt-hour is saved, yet the DUoS bill falls. The same logic explains why EV and time-of-use tariffs for households are cheap overnight: they pass the green-band saving back to you for charging when the network is quiet.

There is also a defensive angle. DNOs apply excess-capacity penalties if your peak demand exceeds the supply capacity you have agreed. Many sites quietly over-pay here for years because their agreed capacity was set high and never reviewed. Matching agreed capacity to real demand is a one-off check that can keep paying back.

What you should actually do

The bottom line

DUoS charges are the local network toll, the biggest single network item on most bills, and the only one with a clock attached. For businesses, the red/amber/green structure turns "when you use power" into real money, and shifting flexible load out of the weekday red band cuts the DUoS bill without cutting output. For households the charge is hidden, but the same logic is why overnight and EV tariffs are cheap. As more solar, batteries and EVs reshape local networks, the time signals baked into DUoS will only matter more.