How UK Data Centres Prove Renewable Energy to Customers: SLA Evidence, Procurement, and Audit Trails

Colocation data centre operators are facing a new kind of procurement pressure: enterprise and hyperscale customers are asking for renewable energy evidence in the same level of detail that they ask for uptime evidence. ISO 27001 and Tier certification have long been the commercial gatekeepers for colocation procurement. Renewable energy certification is becoming the third leg of that stool.

This article explains what the evidence actually needs to look like, which documents prove what, and how on-site solar PV fits into the evidence hierarchy.

What customers are actually asking for

The standard sustainability questionnaire — whether run through CDP’s supply chain module, EcoVadis, or a bespoke customer framework — typically asks some version of these questions:

1. What is your total annual energy consumption (kWh)?
2. What percentage of your energy consumption comes from renewable sources?
3. What is your Scope 2 GHG emissions figure, and which method (location-based or market-based)?
4. Do you hold REGOs, GOs, or PPAs to support your renewable claim?
5. Do you have a science-based or otherwise committed emissions reduction target?
6. Can you provide a metered generation report for on-site renewable assets?

Questions 2, 3, and 4 are where most colocation operators stumble — either because they cannot answer them precisely, or because the evidence they provide does not satisfy the customer’s audit requirements.

The evidence hierarchy

Not all renewable energy evidence carries the same weight with customers’ sustainability teams. In descending order of audit confidence:

Tier 1 — On-site PV with MCS certificate and metered generation data. The generation is at your facility. The MCS commissioning certificate links the system to your specific address. Half-hourly metered generation data (from the inverter monitoring platform) provides a continuous, verifiable record. REGOs issued against this generation are backed by a physical asset that any auditor can inspect. This is the strongest possible renewable energy evidence.

Tier 2 — Dedicated corporate PPA from a named UK generator. A 10–15-year PPA from a named UK wind or solar farm, with GOs issued and transferred per MWh. Auditors generally accept this as high-quality market-based evidence if the generator is UK-based, the GO vintage matches the consumption year, and the PPA is additionality-positive (i.e., the generator was built or would not have been viable without the PPA revenue). The weakness is that there is no physical link between the electrons generated and the electrons consumed.

Tier 3 — Bundled REGOs purchased from the spot market. REGOs purchased from renewable generators without a direct PPA relationship. These certificates are valid under the GHG Protocol’s market-based method, but they face increasing scrutiny: some customers explicitly exclude unbundled certificates from their supplier requirements, particularly if they follow the RE100 technical criteria which prohibit unbundled certificates in some markets.

Tier 4 — Green tariff from a utility supplier. A green electricity tariff from a supplier (e.g., a “100% renewable” tariff from a major utility). These tariffs are REGO-backed but often use certificates from any UK renewable source without vintage matching. Many sophisticated customers now require at least Tier 2 evidence and do not accept standard green tariffs as sufficient.

What on-site solar PV proves — and how to document it

An on-site solar PV installation with MCS certification provides the following verifiable claims:

Claim	Document
A solar PV system exists at your facility	MCS commissioning certificate (includes site address, system size, panel and inverter specifications)
The system was installed to UK standards	MCS certificate (requires NICEIC-registered installer)
The system generates renewable electricity	Half-hourly metered generation data from inverter monitoring
The generated electricity is consumed on-site	Zero-export meter reading confirming negligible export
The generation produces tradeable renewable certificates	REGO registration confirmation from Ofgem (one REGO per MWh generated)
The operator can make a market-based Scope 2 claim	REGO retirement confirmation for the relevant reporting period
The CO₂ avoided is calculable	Annual generation (MWh) × UK grid average emission factor (gCO₂e/kWh)

We provide all of these documents as part of our handover pack, structured for direct submission to customer sustainability questionnaires.

How to calculate and present your Scope 2 figure

Location-based Scope 2: Total electricity consumption (kWh) × UK grid average emission factor. The UK government publishes this annually (DESNZ/Ofgem). For 2025, the UK grid average is approximately 147 gCO₂e/kWh (final figure typically published in Q1 of the following year). On-site solar reduces total grid import and therefore reduces the location-based Scope 2 figure in direct proportion.

Market-based Scope 2: Total electricity consumption (kWh) × emission factor of the contracted supply. For the portion covered by on-site solar REGOs (zero-carbon, emission factor = 0 gCO₂e/kWh) and any portion covered by a renewable PPA or green tariff: the market-based factor for those units is the lifecycle emission factor of the generation technology (solar PV: approximately 30–40 gCO₂e/kWh; wind: 7–12 gCO₂e/kWh). For residual grid import without renewable instrument coverage: use the UK residual electricity emission factor (published by DESNZ as the “supplier mix” figure, which is higher than the grid average because the green-attributed units have been removed from the pool).

A colocation operator with 10,000 MWh total annual consumption, 800 MWh covered by on-site solar REGOs, and the remaining 9,200 MWh on a standard commercial tariff (no renewable attribution):

• Location-based Scope 2: 10,000 × 147 = 1,470 tonnes CO₂e
• Market-based Scope 2: (800 × 35) + (9,200 × 487) = 28 + 4,480 = 4,508 tonnes CO₂e

Note the paradox: the market-based figure is higher than the location-based figure when residual electricity — which carries a high emission factor — makes up most of the consumption. This is why colocation operators who are early in their renewable energy journey should be cautious about reporting market-based figures without adequate renewable instrument coverage.

Responding to specific customer requirements

“We require our suppliers to use RE100-compliant renewable energy instruments.” RE100’s technical criteria (updated 2023) require unbundled certificates to be from the same country as consumption, within two years of the generation vintage. On-site solar REGOs satisfy RE100 criteria — they are UK-generated, same-year vintage, and directly attributable. Standard green tariff REGOs from older vintage or foreign generation may not.

“We require demonstrable Scope 2 reduction rather than just certificate coverage.” This is the strongest requirement and typically comes from customers who have adopted the Science Based Targets initiative (SBTi). SBTi’s corporate net zero standard requires actual Scope 2 reduction (not just certificate coverage) by 2030. For a supplier to demonstrate actual Scope 2 reduction, their location-based Scope 2 must decrease year over year. On-site solar directly reduces location-based Scope 2; purchased certificates do not.

“We require hourly CFE data matched against our consumption.” This is the most advanced requirement, typically from Google, Microsoft, or Amazon as customers. It requires that renewable generation in each hour of consumption be documented. On-site solar monitoring systems can provide hourly generation profiles; EnergyTag Granular Certificates provide an emerging certification framework for hourly matching. We configure our monitoring systems to export hourly generation data compatible with EnergyTag and customer-specific CFE reporting requirements.

Practical steps for colocation operators

1. Install on-site solar — the highest-quality renewable energy evidence, with direct asset linkage to your facility.
2. Register with Ofgem for REGO issuance — via an approved REGO agent (we facilitate this as part of handover).
3. Retire REGOs annually for the previous year’s generation — typically by 31 March of the following year to cover the calendar year.
4. Request a sustainability reporting template from us at handover — we provide a completed SECR-compatible Scope 2 calculation and a CDP-compatible renewable energy disclosure data sheet.
5. Upgrade your SLA documentation to include renewable energy evidence as a deliverable — we see leading colocation operators embedding quarterly generation reports and annual REGO retirement confirmations into customer SLAs.

The colocation market is moving toward renewable energy as a differentiator — then a standard — then a price-of-entry requirement. Operators who establish their on-site PV evidence trail now are better positioned for the procurement cycles of 2026–2028 when these requirements are likely to become universal among enterprise customers.

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We provide a complete sustainability evidence package at installation handover. Contact us to discuss how your specific customer requirements map to the available evidence.