Why are electricity connection costs confusing for housebuilders?
Getting power to a new housing development is not always as simple as asking the local electricity network to connect the site.
For housebuilders, electricity connections can be one of the more confusing parts of the utility process. The quote may include design costs, cable works, substations, legal fees, network checks, inspections, adoption costs, and sometimes reinforcement. On top of that, there are different routes available: you can deal directly with the local Distribution Network Operator (DNO), or you can use an Independent Distribution Network Operator (IDNO), often alongside an Independent Connection Provider (ICP).
Ofgem's guide to electricity distribution connections policy makes clear that connection costs vary depending on the size of the connection, location, distance from the existing network, and whether the network can accommodate the required capacity.
The important point is this: not all connection costs are fixed, and not all works have to be carried out by the DNO. Some works are contestable, which means they can be competitively priced and delivered by others. Other works are non-contestable, which usually means they must be carried out by the local DNO.
Understanding the difference can help housebuilders avoid overpaying, compare quotes properly, and make better decisions before the site programme is locked in.
Who are the DNO, IDNO, and ICP on a housing scheme?
The DNO is the regional electricity network owner. It owns and operates the local electricity network in your area. If you are building homes in Manchester, Birmingham, Kent or Cornwall, there will be a specific DNO responsible for that region.
An IDNO is also a licensed electricity network operator, but it usually owns and operates newer last-mile networks. These are often the networks built to serve new housing estates, apartment blocks, mixed-use schemes or commercial developments. An IDNO network still connects back into the local DNO's wider network. Ofgem's open letter on IDNOs notes that IDNOs serve around 1.5 million customers in Great Britain and adopt a large share of new connections.
An ICP is an Independent Connection Provider. This is an accredited contractor that can design and build parts of the new electricity infrastructure. Once complete, the assets may be adopted by the DNO or by an IDNO.
For a housebuilder, this creates choice. You can ask the DNO to provide the full connection, or you can use an ICP and/or IDNO route for some of the works. National Grid Electricity Distribution's Competition in Connections factsheet sets out the difference between contestable and non-contestable works and explains the role of ICPs and IDNOs.
What are extension assets on a housing development?
Extension assets are the new electrical assets needed to connect your development to the existing network.
For a housing site, this might include:
- new underground cables;
- a new substation;
- low-voltage mains around the estate;
- service cables to plots;
- link boxes, joints and associated equipment;
- ducting, trenching and reinstatement.
Put simply, these are the assets needed to extend the electricity network to your development and distribute power around the site.
These costs usually sit with the developer because they are needed to serve the new homes. Even where reinforcement rules have changed, housebuilders should still expect to pay for the new connection assets required for the development itself. National Grid's Significant Code Review guidance distinguishes extension assets from wider reinforcement in the post-April 2023 charging framework.
What are contestable works?
Contestable works are the parts of the connection that can be opened up to competition. This means the DNO does not have to do all of the work. A suitably accredited ICP can often design and build much of the new network, and an IDNO may adopt it afterwards.
Typical contestable works can include:
- the design of the new network extension;
- buying and supplying materials;
- trenching and excavation;
- installing cables;
- building substations;
- carrying out some low-voltage works;
- providing as-laid drawings and test records;
- obtaining some third-party land rights.
This is where housebuilders can often create savings or programme benefits. Instead of simply accepting a full DNO quote, you may be able to get competitive prices from ICPs and IDNOs.
It is not just about cost either. On some developments, the competitive route may offer more flexibility around phasing, design coordination, site access and delivery dates. UK Power Networks' guidance on ICP works provides examples of works an ICP or IDNO may carry out where the DNO is only undertaking non-contestable works.
What are non-contestable works?
Non-contestable works are the parts of the connection that usually have to be carried out by the local DNO. That is because these works affect the existing public electricity network. The DNO is responsible for keeping that network safe, reliable and compliant.
Non-contestable works can include:
- confirming the point of connection;
- checking available capacity;
- approving designs;
- inspecting works before adoption or energisation;
- completing certain final connections;
- carrying out work on the existing DNO network;
- dealing with some statutory wayleaves;
- assessing reinforcement requirements.
Even if you choose an ICP or IDNO route, the DNO does not disappear from the project. The DNO will still be involved because your site ultimately connects into its network.
That is why housebuilders should be careful when comparing quotes. A cheaper ICP or IDNO proposal may still rely on a separate DNO non-contestable quote. To compare properly, you need to understand the total cost, not just one part of it.
Should you use the DNO route or the ICP/IDNO route?
There are usually two broad routes.
The first is the DNO route. This is where the local DNO provides the connection offer and may carry out both the contestable and non-contestable works. This can be straightforward, particularly for smaller or simpler sites, but it may not always be the most commercially attractive option.
The second is the ICP/IDNO route. Under this route, an ICP may design and build the new connection assets, and an IDNO may adopt and operate the new network once it is complete. The host DNO still deals with the connection into its existing network, but the new estate network may be owned by the IDNO.
For housebuilders, the IDNO route can be attractive because IDNOs may offer an asset value or asset adoption payment. In simple terms, this is a payment linked to the IDNO adopting the new network and earning future network charges from it. This payment can reduce the net cost of the connection.
However, it is important to check the details. You should understand who receives the asset value, when it is paid, whether it is included in the contractor's price, and whether there are any conditions attached. A headline saving is useful, but only if it is clear, secure and properly reflected in the commercial agreement.
What is the difference between extension assets and reinforcement?
Reinforcement works are different from extension assets. Extension assets are the new assets needed to serve your site. Reinforcement works are upgrades to the existing wider network because it does not currently have enough capacity. For example, reinforcement could involve upgrading an upstream cable, transformer or substation.
This is a bigger topic, and the rules changed from April 2023 following Ofgem's Access and Forward-Looking Charges Significant Code Review. In many standard demand connection cases, such as new housing, developers no longer pay a contribution towards upstream reinforcement in the way they used to. However, there are exceptions, including high-cost demand schemes and speculative developments.
We cover this separately in our article on why sites ruled out for electricity reinforcement may deserve a second look.
For this article, the key point is simple: do not confuse reinforcement with extension assets. Even where reinforcement costs are reduced or removed, the developer will still usually pay for the new assets needed to connect the development itself.
How should housebuilders compare connection offers and control cost?
The connection quote is not always the full picture. Depending on the site, developers may also need to allow for off-site easements or wayleaves, substation land transfer or lease arrangements, planning requirements for substations, traffic management, road opening notices, temporary building supplies, ducting and trenching by the groundworker, meter positions, MPAN registration, legal fees, and abortive costs if the layout or load changes.
A common issue is that the electrical design moves after the utilities process has already started. Plot numbers change, EV charging assumptions change, heat pump loads increase, or the substation location moves because of planning or drainage constraints. Each change can affect the connection design, the programme and the cost. The earlier the electrical strategy is considered, the easier it is to control.
The best way to compare offers is to break them down into clear sections. Ask:
- What are the contestable works?
- What are the non-contestable DNO costs?
- What extension assets are included?
- Who will own and operate the assets after completion?
- Is there an IDNO asset value payment?
- Is any reinforcement included or excluded?
- Are legal, civils, easements and temporary works included?
- What assumptions have been made about load, phasing, EV charging and heat pumps?
Two quotes can look very different on paper but include different scopes. One may include civils and legal costs. Another may exclude them. One may show an IDNO asset value. Another may not. One may assume a different point of connection. The cheapest headline number is not always the cheapest final cost.
For housebuilders, electricity connections should be treated as a commercial strategy, not just a utility application. The earlier you look at load, phasing, substation locations, duct routes and adoption options, the more control you have. Contestable works are the parts you may be able to shop around. Non-contestable works are the parts that usually stay with the DNO. Extension assets serve your site. Reinforcement should be reviewed separately.
For many developments, the best route may be a competitive ICP/IDNO solution, especially where an asset value payment helps reduce the net cost. For others, a direct DNO route may still be suitable. The important thing is to compare like-for-like, challenge assumptions early, and make sure the connection strategy supports the build programme rather than holding it up.
HubbPro does not manage connection applications or compare DNO and ICP quotes. It helps housebuilders establish kVA demand, export capacity and FHS assumptions earlier, so utility consultants can advise on contestable routes and connection strategy with a clearer brief before layout and PoC figures become expensive to change.