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Power resilience for a net zero world

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Explaining DNOs






Your organisation has committed to a robust sustainability strategy, you’ve made changes to staff behaviour and operations, and now you are ready to take the next major step and install on-site infrastructure. Maybe you are looking to generate clean energy on-site through rooftop solar PV, or support a transition to an EV fleet through rapid charging stations. The project has been planned, budgeted for and drawn up. Then, your DNO turns down the application, blocking the project’s implementation.


The infrastructure that moves power around the UK and delivers it to end users is split into two classifications; transmission networks, and distribution networks. Transmission networks are those of National Grid themselves, high-voltage infrastructure including transmission lines and substations. These voltages are much too high to be delivered safely to end users, which is where distribution networks come in. This is the electrical infrastructure that allows individual homes and businesses to access transmission networks. The owners and operators of this infrastructure are known as Distribution Network Operators, commonly shortened to DNO.

There are currently 14 DNO licence holders in the UK, owned by six different organisations. Each licence holder is responsible for the infrastructure across a specific geographic area. The six organisations are UK Power Networks, Western Power Distribution, SP Energy Networks, Electricity North West, SSE and Northern Powergrid.

DNOs are responsible for maintaining and upgrading the distribution network infrastructure within their region. They recover the costs of this work through the use of Distribution Use of System (DUoS) charges, part of the non-commodity costs paid by all bill payers.


DNOs have found themselves at the sharp end of the UK’s growing issues surrounding power resilience. Much of their infrastructure was originally designed to delivery power one way, from the transmission network to end users. However, the rapid growth of distributed generation now means that much of their infrastructure is required to juggle power flows in both directions. This can quickly put strain on transformers and other infrastructure, potentially even risking overloading it and causing a disruption event.

DNOs face stiff penalties from Ofgem in the event of their customers experience significant disruption, and part of their role now is to monitor and police proposed projects that would put additional strain on their infrastructure. Large power infrastructure projects require an application to be submitted to your DNO for approval. If they feel that it could cause localised disruption, they have the ability to reject it outright. This can potentially apply to additional generation, such as a solar array or wind turbine, and significant increases in your site demand such as EV charging.


It can be difficult to know where to turn once your DNO turns down a project. I can be tempting to try and purchase a new grid connection to up your site’s authorised capacity, but this is often impractically expensive at best. Increasingly, a project is turned down for the same reason that a new connection may simply not be possible: there is too much localised demand on your distribution network already.

In this situation, there is fortunately one technology you can turn to that has the potential to unlock a project that might otherwise seem to be falling through. Using a battery energy storage system (BESS) allows your on-site infrastructure to be insulated from your grid connection, removing the risk of a sudden surge in either generation or demand impacting on your distribution network. Excess on-site generation that could otherwise spill out of your site onto the grid can be stored for later use, while high-demand technologies, such as rapid EV charging, can be charged partially or entirely using stored energy rather than increasing your site’s total draw from your grid connection. The BESS can be charged slowly from grid power, as well as through on-site generation. When a ramp in power is required, it is taken from the battery to ensure there is no demand spike causing issues for your DNO.

Powerstar’s digital modelling capabilities allow you to demonstrate to your DNO that a project will work entirely as intended, without proposing a risk to your distribution network. By building a digital replica of your site and infrastructure, new installations can be tested extensively under a range of different factors. This ensures that a proposed technology solution can be proven in concept before being commissioned and installed, providing peace of mind for customer and DNO alike. 

To find out more about how our BESS solutions can help to support your wider sustainable technology ambitions, contact our team today

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