Voltage can’t wait: Why ED3 must be the moment we act
Ofgem has been warned. Voltage on local networks is running too high, the easy fixes are nearly used up, and the grid edge is becoming a system security issue. The Energy Geeks set out their view on why the ED3 price control offers industry a chance to get this right.
Voltage can’t wait: Why ED3 must be the moment we act
Ofgem has been warned. Voltage on local networks is running too high, the easy fixes are nearly used up, and the grid edge is becoming a system security issue. The Energy Geeks set out their view on why the ED3 price control offers industry a chance to get this right.
Voltage has been the forgotten issue in the net zero network debate. Capacity, connection queues and flexibility markets get the attention, while voltage is quietly managed at the substation. The IET's Voltage Management Task & Finish Group, set up at Ofgem's request in August 2025, says that can't continue.
Its message is clear. More active voltage management is both possible and necessary. Most of the tools already exist. What's missing is visibility at the grid edge, coordination between the different parts of the system, and governance. The IET Group believes we have time to act within normal industry timescales, but only if we start now. If heat pumps, electric vehicles (EVs) and solar arrive faster than planned, that time shrinks. Every year customers are paying more for wasted energy and the system is having to take remedial actions.
There is evidence to suggest that up to one in 20 low voltage customers may be regularly supplied above the 253V legal limit. More than a fifth of monitored EV chargers have tripped out. Some solar inverters are disconnecting at voltages they are meant to ride through.
The Energy Geeks are a thinktank set up to tackle the thorniest issues of energy policy. They are: Eric Brown; Maxine Frerk; Simon Harrison; Roger Hey; Laura Sandys and Steven Steer
Historically, the UK operated at 240V, but in the 1990s, as part of harmonisation with the EU, the nominal voltage was changed to 230V (with an allowed range of 216V to 253V). However, most networks kept working on the basis of 240V and homes typically receive 243V, even with minimal export from solar PV panels. More solar export pushes up the voltage. The usual fix, turning voltage down at primary substations, is nearly exhausted. Many transformers are already close to the bottom of their tap range, leaving little room for further reduction or for the emergency demand control the National Energy System Operator (NESO) can call on.
The national picture is shifting too. Transmission demand hit a record low of 12.62GW on 24 May 2026. With 45 to 47GW of solar targeted by 2030, local networks will increasingly push power back into higher voltage networks, including potentially the transmission grid.
Lessons from Iberia
The Iberian blackout on 28 April 2025 highlighted how voltage control and distributed generation behaviour can become critical system issues. The loss of active power export due to generators tripping on overvoltage exceeded the loss of demand from active load shedding, leading to frequency continuing to fall until the system collapsed and hence the blackout occurred. GB is better protected, with an islanded system, stronger grid rules and NESO's stability services; but the IET is clear: the underlying risk is real and calls for action, not reassurance.
The encouraging news is that we don't need to wait for new technology. Network operators have spent years trialling smarter voltage control. Northern Powergrid's Boston Spa Energy Efficiency Trial (BEET) uses smart meter data to optimise primary substation voltages. Other DNOs are testing devices that manage voltage at the local substation level. What's holding us back is not the kit but visibility, coordination and governance.
There are a number of reasons why inaction is costly:
We're leaving savings on the table. Trials such as the BEET project have shown that reducing voltage by a few percent can cut energy consumption and hence reduce customers’ bills. The BEET trail calculated that the savings could be as much as 4%.
Customer confidence is at risk. Solar that trips in June and heat pumps that struggle in January are failures people notice and talk about. If networks can't keep up, the IET report warns we could end up limiting how fast people can connect low carbon technologies (LCT). That would undermine Clean Power 2030 and the Warm Homes Plan and affect some regions much harder than others.
Delay makes it more expensive. Once the cheap substation-level options run out, control has to move closer to homes, through smarter local transformers, new power electronics and inverters that actively support voltage. Each step needs appropriate regulatory support for investment and commercial arrangements that don't yet exist. Starting early keeps the cost down.
Security of supply now starts on our streets. A growing proportion of new generation connects to local networks or sits behind the meter. How millions of small inverters behave in a voltage disturbance now shapes how the whole system copes with a shock, yet NESO can see very little of it.
The rulebook is the real bottleneck. Our codes and standards move too slowly and have too little bite on compliance. The technical answers exist. The machinery to roll them out at scale does not… yet.
What about older appliances? Some will ask whether lower voltage is safe for equipment designed for the old 240V standard. Everything proposed here sits inside today's legal range of 216 to 253V. Bringing the average down from 243V towards 230V moves most homes closer to the voltage their appliances were designed for, not further away. Many customers at the end of long feeders already live in the low 220s without trouble, and large trials such as Electricity North West's Customer Load Active System Services (CLASS) found no customer problems.
The real overheating risk today comes from voltage that is too high. Questions about the proposed 207V floor deserve proper testing through the Energy Networks Association (ENA) trials, but they are no reason to keep paying for wasted volts now.
ED3: the window is open, but not for long
Ofgem has done its part to open the door. Its ED3 methodology decision in May 2026 made voltage management a formal job for Distribution System Operators (DSO) for the first time. They must publish a Voltage Management Strategy, improve monitoring, and keep reactive power in check at the boundary with the transmission grid.
But an obligation is not a plan. Final business plans are due before the end of the year, covering April 2028 to March 2033. Whatever isn't in them will be hard to fund before the 2030s unless uncertainty mechanisms come to the rescue. The IET report is, in effect, a ready-made starting point for what those strategies should contain. It would be a wasted opportunity not to use it.
ED3 is also only one of several moving parts that need to line up; all have a contribution to make:
No single organisation can fix this alone. Each player has a clear next step.
The message for network operators is to put voltage at the heart of your ED3 plans. Show how many customers are over the limit today, how much adjustment is left at each substation, and a costed route to bring average voltage supplied down to within a range of 220-240V consistent with typical domestic electrical appliance ratings. Scale up the proven tools from your own innovation portfolios rather than starting again.
To Ofgem, we say hold the bar high. Treat voltage management strategies as a test of plan quality, not a box to tick. Fund proven techniques as business as usual and build in adaptability so networks can move faster if LCT uptake outruns forecasts. Keep timescales under review and be ready to accelerate.
It is for government to settle the voltage limits. It must back the ENA trials now and take a timely decision on the wider legal range. Every month of uncertainty delays the cheapest fix available.
Manufacturers and standards bodies can make inverters part of the solution. They must make sure solar and EV equipment rides through voltage disturbances as specified, backed by real testing and enforcement. Then go further, so inverters actively help manage voltage. Appliance makers should confirm their products perform well at the lower end of the band.
NESO and DSOs have a responsibility to share what they see. They can build a common picture of where small-scale generation is and how it behaves under stress. We also task them with agreeing who buys voltage support from batteries and solar, before the market gets confused. Then the whole system can be modelled together.
Code bodies need to fix the rulebook. Code reform must give technical standards a faster route to change and real teeth on compliance. Without that, good engineering will keep stalling on process.
In parallel with the other actions and not as a pre-condition, work should be undertaken to close the remaining evidence gaps on very old and motor-driven equipment referred to in the IET report, the Engineering Standards Review and elsewhere. This could include looking at the experience of other countries such as New Zealand.
The IET's final report will add detail on the importance of addressing voltage management, but with ED3 plans due within weeks, nobody should wait for it. Voltage is no longer a backroom engineering issue. It is a test of whether the industry can move fast enough to keep the energy transition on track. The cheapest decade to fix it is the one we are about to price. Let's not miss it.
