IN Brief:
- DESNZ has published research by Ramboll on innovative underground transmission cable methods.
- Cable ploughing, HDD, and microtunnelling were identified as the alternatives with the strongest potential.
- Cable ploughing could reduce civil works costs substantially where ground conditions and route constraints are suitable.
The Department for Energy Security and Net Zero has published a Ramboll study examining whether alternative undergrounding methods can reduce the cost and disruption of high-voltage transmission cable installation.
The report compares conventional cut-and-cover with cable ploughing, horizontal directional drilling, microtunnelling, auger boring, Direct Pipe, E-Power Pipe, and Pipe Express. It considers whether these methods could reduce costs over 20km and 50km transmission routes, while also reviewing technical feasibility, environmental impact, and whether each method can provide a complete route solution.
Ramboll identifies cable ploughing, HDD, and microtunnelling as the alternatives with the strongest potential to compete with conventional cut-and-cover in suitable conditions. Cable ploughing shows the greatest civil engineering cost-reduction potential, while HDD is best suited to crossings and constrained sections rather than whole-route replacement.
The modelling indicates that cable ploughing could reduce civil works costs to 28% to 34% of cut-and-cover costs where routes are appropriate. Because cable materials represent a large proportion of total project cost, the overall project saving is smaller, with total build costs potentially falling to 60% to 80% of cut-and-cover levels under suitable assumptions.
The findings arrive as grid expansion becomes one of the UK’s most significant civil engineering workloads. Offshore wind, renewable connections, electrification, data centres, EV charging, and industrial power demand are forcing transmission and distribution projects out of long-term planning cycles and into active delivery pipelines.
At distribution level, network development plans are setting out where demand growth, generation, and electrification will create local constraints. Across the wider system, low-demand grid operation is already being shaped by renewables, storage, interconnectors, and flexibility services.
Undergrounding remains one of the most contested parts of network delivery because it sits at the intersection of planning, cost, environmental impact, land access, community acceptance, and technical risk. Overhead lines remain cheaper and faster in many cases, but underground cables are often considered where visual impact, protected landscapes, political pressure, or landowner concerns make pylon routes difficult.
The report does not present trenchless and ploughing methods as universal replacements for cut-and-cover. Cable ploughing is constrained by obstacles, geology, terrain, route complexity, and joint bay requirements. HDD is well established for crossings, but becomes more expensive and technically difficult when applied over long routes, particularly as cable rating and voltage increase. Microtunnelling is proven, but launch shafts, plant, and costs limit its competitiveness over extended alignments.
Route planning will therefore remain decisive. Underground cable cost is shaped by ground investigation, thermal performance, cable rating, joint spacing, environmental constraints, haul roads, spoil handling, crossing strategy, temporary works, and reinstatement. Method selection can reduce cost only where those factors align.
The construction opportunity will favour companies able to combine cable installation knowledge with geotechnical, trenchless, environmental, and logistics capability. Clients need approaches that reduce disruption without introducing unmanageable risk, especially as major network projects move through planning and procurement. DESNZ’s study gives the market a clearer evidence base for assessing where innovation can reduce cost, and where conventional methods will remain necessary.
