The short answerThe DNO owns the regional electricity network and always does certain jobs, such as the final connection. An IDNO is a licensed company that owns and runs the local network on a new site, usually a housing development. An ICP is an accredited contractor that can build the parts of a connection that are open to competition, which the DNO or an IDNO then adopts.
What is a DNO?
A distribution network operator (DNO) is the licensed company that owns and runs the electricity cables, overhead lines and substations in a region. It carries electricity from the national transmission system to homes and businesses. It does not sell you electricity. That is your energy supplier's job.
Great Britain has 14 DNO licence areas, run by five DNO groups. You can't choose your DNO. It is fixed by where the site is.
- UK Power Networks: London, South Eastern and Eastern.
- National Grid Electricity Distribution (NGED): West Midlands, East Midlands, South West and South Wales.
- SSEN: Southern, and North of Scotland.
- SP Energy Networks: SP Manweb (Merseyside, Cheshire and North Wales) and SP Distribution (Central and South Scotland).
- SP Electricity North West: the North West. This was Electricity North West until it was bought by the ScottishPower group and renamed in 2025, which is why it now sits under the same owner as SP Energy Networks.
- Northern Powergrid: the North East and Yorkshire.
In Wales, NGED covers the south and SP Manweb covers North and Mid Wales. Ofgem publishes the full list of electricity licensees. You will still see older websites say there are six DNO groups. That stopped being true in 2025.
What is an IDNO?
An independent distribution network operator (IDNO) also holds an Ofgem licence to own and run electricity networks. The difference is scale. IDNOs mostly own the local network inside new sites, such as the cables and substation serving a housing estate. That local network connects to the host DNO's network at the site boundary or nearby.
For the people who live there, very little changes. They still pick any energy supplier they like. Ofgem caps an IDNO's domestic use-of-system charges at the host DNO's equivalent charge, so households are not charged more for being on an IDNO network.
For a developer, an IDNO is another company that can own the site network and take responsibility for it after it is built. On larger sites, that can change the overall cost and who you deal with on the programme.
What is an ICP?
An independent connection provider (ICP) is a contractor that designs and builds connection work to the network operator's standards. To do this it must be accredited under the National Electricity Registration Scheme (NERS), which is run by LRQA on behalf of the DNOs. Each ICP is accredited for specific types of work, such as design, cable laying or substation installation, and up to particular voltages.
An ICP does not own the network it builds. Once the work is finished and inspected, it is adopted by the DNO or an IDNO, which then owns and maintains it. You can check a provider's scope on the LRQA NERS pages.
Contestable and non-contestable work: what can go to competition?
Every connection is split into two kinds of work. Contestable work can be done by an accredited ICP or by the DNO, so you can get competing prices. Non-contestable work can only be done by the DNO.
| Contestable (ICP or DNO) | Non-contestable (DNO only) |
|---|---|
| Design of the extension, and of contestable reinforcement | Processing applications, and adopting the finished work |
| Buying materials to the DNO's specification | Final connection and energisation (in some areas accredited ICPs can make some final connections) |
| Trenching, building the extension and reinstatement | Most reinforcement, and diversions of the existing network |
| Record drawings, metering provision and legal consents | Inspecting the contestable work, then operating and maintaining the network |
One detail matters a lot. The point of connection is where your new cables join the existing network. Choosing it is technically non-contestable. Under the Competition in Connections Code of Practice, though, an ICP can self-determine the point of connection and self-approve its design, within its accreditation. That can save time, because the ICP doesn't have to wait for the DNO to do that part.
How the three fit together on a real project
Most connections follow one of three routes. The right one depends on the size of the job and what you care about most: price, programme or simplicity.
| Route | Who builds | Who owns it after | Often suits |
|---|---|---|---|
| DNO only | DNO | DNO | Single homes, small upgrades and simple supplies |
| ICP and DNO | ICP (contestable), DNO (non-contestable) | DNO | Developments and commercial sites where you want more control of price or dates |
| ICP and IDNO | ICP (contestable), DNO (connection to its network) | IDNO | Larger housing sites with an on-site network and substation |
Whichever route you take, the DNO is still involved. It provides the point of connection to its network and does its non-contestable work, so its timescales still count.
When is a second offer worth getting?
For a single new home, the DNO is often the simplest choice. There is little contestable work, and one application with one company is easier to manage. On developments, commercial units and anything needing a substation, the contestable part is bigger, and comparing offers is far more likely to pay.
When we compare offers, we look at more than the headline price:
- Scope. Does each offer include the same trenching, reinstatement, substation works and meter positions?
- Exclusions. Who does the digging on your land, and are highway permits, traffic management and wayleaves included?
- Reinforcement. Since 1 April 2023, demand connections pay for extension assets only. Wider reinforcement is paid through network charges, except above Ofgem's High Cost Cap of £1,720/kVA or for assets used only by you. Check that each offer applies this correctly.
- Fees. Since 2018, DNOs can charge assessment and design (A&D) fees for preparing an offer, whether or not you accept it. When the fee is charged varies by DNO and type of scheme.
- Validity. Each operator sets how long its offer stays open. 90 days is common, but always check the offer letter.
- Dates. The DNO's non-contestable work and final connection still have to fit around everything else.
Common mistakes
- Assuming the DNO is the only option. On multi-plot sites, many people never ask for an independent price.
- Comparing totals, not scope. A cheaper offer that leaves out trenching or reinstatement can end up costing more.
- Using a provider outside its accreditation. NERS scopes are specific. A provider accredited for cable laying may not be accredited for substation design.
- Leaving out future load. Heat pumps, EV chargers, solar and batteries need to be in the application, or the network may be sized too small.
- Letting offers expire. An expired offer can mean a new application and, with some DNOs, a new fee.
How we help
We don't build networks, and we don't own any. That means we can tell you honestly which route suits your site. We confirm the DNO for your area, prepare the application, ask independent providers to quote where it makes sense, and set the offers side by side so you can choose. Then we manage the acceptance and dates through to energisation. Read more about our electricity connection service.