Edge Data Centre Solar in the UK: Economics, Installation Constraints, and the 50–200 kW Case

The UK’s edge computing infrastructure is growing faster than most people in the industry realise. Every major mobile network operator (BT/EE, Vodafone, O2, Three) is deploying Multi-access Edge Computing (MEC) nodes at base station clusters and exchange buildings. Every major content delivery network (CDN) — Akamai, Cloudflare, Fastly — is building or leasing edge PoPs in secondary UK cities. Colocation operators are building micro-data centres in industrial estates serving regional enterprises that need sub-10ms latency to local users.

These edge facilities are typically small: 50–500 kW of IT load, often in a converted telecoms exchange, an industrial building, or a purpose-built 20-foot container. They are geographically dispersed across the UK — not just in London and Slough, but in Ipswich, Wolverhampton, Plymouth, Inverness.

Can solar PV work at this scale? The short answer: yes, and the economics are underappreciated. Here’s the detailed case.

The edge solar economics case

A 100 kW edge data centre drawing £180,000/year in electricity costs (at 22p/kWh for a 750 kW IT load with 1.4 PUE — approximately 818,000 kWh) is a relatively small load. A rooftop PV system sized to the building might be 50–120 kW. At 1,450 hours irradiance (a reasonable UK average), a 100 kW system generates 100,000 kWh/year — covering approximately 12% of total consumption.

At 22p/kWh, that is £22,000/year in avoided cost. Capital cost: £85,000–£120,000. Full Expensing tax relief (25% CT rate): £21,250–£30,000 in year one. Post-tax net cost: £63,750–£90,000. Simple post-tax payback: 2.9–4.1 years.

This is better payback than most large data centres achieve, for two reasons:

1. Small systems are relatively more expensive per kW — capital cost per kW for a 100 kW system (£850–£1,200/kW) is higher than for a 500 kW system (£750–£900/kW). But the Full Expensing relief scales proportionally, and the avoided grid rate is the same.
2. Edge facilities often have premium grid tariffs — edge nodes in urban or semi-urban locations frequently pay 23–28p/kWh versus the 18–22p/kWh typical of large rural data campuses. The higher the grid rate, the better the solar economics.

Grid connection at small scale: G98 vs G99

The G98/G99 boundary — 50 kW three-phase (approximately 16 A per phase) — matters enormously for small edge installations.

Below 50 kW (G98): Self-certification. No DNO application, no waiting period, no relay settings negotiation. The installer registers the system with the DNO after installation via the DNO’s G98 portal. Connection is effectively immediate after commissioning. This is the route for edge nodes in small exchange buildings, container deployments, and micro-data centres.

Above 50 kW (G99): DNO application required. The DNO reviews the proposed connection and agrees relay settings. Standard processing: 65 working days (approximately 13 weeks). For an edge facility whose landlord or operator wants solar quickly, this timeline can be a project constraint — plan the G99 application before signing the installation contract, not after.

For edge facilities where a 50 kW system satisfies the economic case (most sites below 500 kW IT load), staying below the G98 threshold is worth considering. It simplifies the project significantly and removes the DNO timeline risk.

Building types and roof constraints at edge scale

Edge data centres come in several building types, each with different solar installation constraints:

Converted telecoms exchange buildings (BT openreach, Virgin Media): These are typically 1950s–1980s flat-roof concrete construction, often listed or in conservation areas (telecoms infrastructure was installed in town centres). Heritage constraints can restrict visible panel installations. Roof structural loading is often limited — telecoms exchanges were not designed for heavy plant. We specify lightweight frameless mounting at 10–12 kg/m² for these buildings. Available roof area after telecoms equipment (dishes, antennae, cable management) is typically 30–60% of gross area.

Industrial estate edge nodes: Modern edge colocation units in business parks (often 500–2,000 sqm, steel portal frame, profiled steel or membrane roofing) are the easiest buildings to work with. Good structural loading, clear roof area, no heritage constraints, good grid infrastructure from nearby primary substations. PV systems of 60–200 kW are straightforward on most post-2000 business park buildings.

Container and modular edge units: Self-contained modular data centres (e.g., Huawei IDataCenter2.0, Vertiv prefab solutions) can be solar-integrated at manufacture or retrofitted with rooftop mounting. A 20-foot container unit supports approximately 4–6 kW of rooftop PV — meaningful only as a contribution to auxiliary power (lighting, monitoring, cooling fans) rather than IT load. Ground-mounted arrays adjacent to container clusters are more practical for meaningful generation.

Retail and commercial building edge nodes: CDN edge nodes co-located in retail units, airport terminals, and commercial buildings use the host building’s existing electrical infrastructure. Solar on the host building requires host landlord permission and potentially integration with the landlord’s electricity supply metering — more complex than a standalone data centre building. These sites are best evaluated case-by-case.

The sustainability case for edge solar

Edge data centres collectively represent a significant and growing portion of the UK’s data centre energy consumption — and one that is currently largely invisible in the sustainability reporting of the operators who run them. A mobile network operator with 2,000 edge nodes across the UK, each drawing 200 kW of average load, has a total edge infrastructure energy consumption of approximately 3,500 GWh/year — comparable to a medium-size hyperscale campus.

That energy consumption is distributed across 2,000 locations, many of which have rooftops. Rooftop solar on even 20% of those sites — 400 sites, each averaging 60 kW of rooftop capacity — would generate approximately 35 GWh/year. At the MNO’s average grid rate, that is approximately £7 million in annual avoided cost across the portfolio, with capital of £20–30 million and Full Expensing relief of £5–7.5 million in year one.

The fleet approach also simplifies procurement: a single EPC contract covering 50+ sites, a single G98 self-certification process per site (assuming systems below 50 kW), a single MCS certification under the installer’s commercial MCS number, and a consolidated sustainability reporting pack covering the entire portfolio.

Procurement considerations for edge solar portfolios

For operators with 10+ edge sites, we recommend a portfolio procurement approach:

Stage 1 — Desktop feasibility across the portfolio. We assess each site against: roof area (satellite/aerial photograph), estimated roof structural capacity, grid tariff (from half-hourly meter data or estimate), irradiance (location-based), and any known planning constraints. This produces a ranked portfolio of sites by post-tax payback. Typical cost: £500–£800 per site at desktop stage.

Stage 2 — Full survey for top-ranked sites. Physical roof inspection, structural engineer assessment, DNO pre-application (or G98 confirmation), and financial model. Typical cost: £2,000–£3,500 per site at survey stage.

Stage 3 — EPC contract for the first tranche. 10–20 sites in a single EPC (Engineering, Procurement, Construction) contract, giving the operator economies of scale on procurement (bulk panel pricing, shared project management overhead) and the installer economies on mobilisation.

Stage 4 — Parallel installation programme. With pre-agreed panel and inverter specifications, sites can be installed by parallel teams. We have completed 8-site parallel programmes in under 12 weeks on business park portfolios.

The portfolio approach typically reduces per-site installation cost by 12–18% versus single-site procurement, while enabling consolidated sustainability reporting and a single SECR disclosure covering the entire renewable portfolio.

---

If you operate a distributed edge data centre portfolio and want a desktop feasibility assessment across your sites, contact our team — we can turn around a portfolio screening in two weeks.