Scope 2 reporting for UK offices — methods, DEFRA factors and how solar cuts your number

Scope 2 emissions explained: what counts and why it dominates office footprints

Scope 2 emissions are the indirect greenhouse gas emissions that arise from the electricity, heat, steam and cooling an organisation purchases and consumes. They are "indirect" because the combustion happens at a power station you do not control, but you cause them by drawing the energy. For an office occupier, that means almost entirely purchased grid electricity — the power running lighting, HVAC, lifts, IT, server rooms and small power across the floorplate.

The GHG Protocol categorises corporate emissions into three scopes. Scope 1 covers direct emissions from sources the organisation controls — gas boilers, company vehicles, refrigerant leaks. Scope 3 covers indirect value-chain emissions — supplier emissions, employee commuting, business travel, purchased goods and services. Scope 2 sits between them and, for offices specifically, usually dominates the directly-controllable footprint.

For most UK office occupiers, Scope 2 represents 60-90% of total Scope 1+2 emissions. A modern office has little on-site combustion — heating is often electric or heat-pump based, there are few or no company vehicles attached to the building, and there are no industrial processes. The carbon story is therefore an electricity story, which is precisely why on-site solar is so material for offices: it attacks the largest, most controllable line in the inventory.

UK grid electricity carries a carbon intensity averaging around 0.21 kg CO₂e per kWh under location-based methodology for 2024 — meaning a typical office consuming 1 GWh per year generates roughly 210 tonnes of Scope 2 emissions annually. On-site solar PV displaces grid electricity at the meter: under both location-based and market-based Scope 2 methods, every self-consumed kWh counts as zero-emission electricity.

Scope 2 reporting in the UK: the GHG Protocol dual-reporting rule

Scope 2 reporting in the UK follows the GHG Protocol Scope 2 Guidance, which requires organisations to disclose purchased-electricity emissions under two parallel methods — and to report both figures rather than cherry-picking the lower one. Getting this right is the single most common technical stumbling block in commercial energy reporting, so it is worth setting out clearly.

The location-based method uses the average emissions intensity of the grid in the geography where the electricity is consumed. For UK consumption it is the DEFRA / DESNZ factor for the year — approximately 0.21 kg CO₂e/kWh for 2024. It reflects the physical reality of the grid and changes annually as generation decarbonises. The market-based method uses contractual instruments — REGOs, GO certificates, PPAs, and on-site generation — to claim specific emissions factors per kWh purchased. A site on a 100% renewable tariff with full REGO coverage can report 0 kg CO₂e/kWh under market-based, regardless of the underlying grid mix.

For on-site solar, both methods credit the self-consumed generation: location-based recognises the avoided grid kWh, and market-based recognises the on-site generation as zero-emission and physically traceable. We provide both calculations in the commissioning documentation pack.

Location-based vs market-based Scope 2 reporting compared

How to report Scope 2 emissions: a 5-step worked example for an office

There is no mystery to the calculation — it is arithmetic applied to the right factor. Here is the method we walk customers through, with a worked example for a mid-size office running a 280 kWp rooftop array.

1. Gather your half-hourly electricity data. Pull 12 months of metered consumption in kWh from your half-hourly meter or supplier statements. Our worked office consumes 1,000,000 kWh/year before solar.
2. Choose your reporting method. Calculate both location-based and market-based — the GHG Protocol requires both to be disclosed. Below we run the location-based figure.
3. Apply the DEFRA grid factor. Use the factor for the year you are reporting. For 2024 that is approximately 0.21 kg CO₂e/kWh. Pre-solar: 1,000,000 kWh × 0.21 = 210 tonnes CO₂e.
4. Deduct self-consumed solar. The 280 kWp array generates around 258,000 kWh/year, of which 78% (≈201,000 kWh) is consumed on site. Grid import falls to 799,000 kWh: 799,000 × 0.21 = 168 tonnes CO₂e.
5. Disclose both figures. Report the location-based total, the market-based total, the intensity ratio (tonnes per FTE or per m²), and the methodology statement in your SECR or annual report. The solar contribution — about 42 tonnes CO₂e/year avoided — also strengthens your SECR energy-efficiency-actions narrative.

That 42-tonne reduction is the figure that lands on the page of the annual report. It is repeatable year after year for the 25-year-plus life of the system, and it grows in significance as a percentage of the total footprint while the rest of the business decarbonises.

UK grid carbon intensity by year (DEFRA factors)

The location-based factor is not static — it falls every year as coal leaves the grid and renewables grow. Always apply the factor for the specific reporting year. The trajectory below also shows why acting now matters: the carbon value of a kWh of solar self-consumption is highest in the early years.

Source: UK Government GHG Conversion Factors (DEFRA / DESNZ), published annually; projections per the Clean Power 2030 trajectory. Use the published factor for the exact year you are reporting.

Commercial energy reporting obligations for UK offices (SECR, ESOS, TCFD)

Commercial energy reporting in the UK is not a single regime but a stack of overlapping obligations, and which ones bite depends on your size and structure. The three most office-relevant are SECR, ESOS and TCFD, with PPN 06/21 added if you bid for large central-government contracts. Solar PV is a recurring, evidenced answer across all of them — it is an energy-efficiency action under SECR, a recommended measure under ESOS, a transition opportunity under TCFD, and an emissions-reduction project under PPN 06/21.

Who must comply with UK commercial energy reporting

Public-sector offices sit outside SECR but report under the Greening Government Commitments and can fund the underlying solar through Salix and the Public Sector Decarbonisation Scheme — see our solar for public-sector offices guide for the funding routes and Green Book business-case detail.

Three ways an office cuts Scope 2: on-site solar vs PPA vs green tariff

There are three practical levers an office can pull to reduce its reported Scope 2 emissions, and they are not equal in either cost or credibility. Auditors and rating agencies increasingly distinguish between claims that put new renewable capacity onto the system (additional) and claims that simply re-allocate existing certificates. The table below ranks the three on the factors that matter when the figure has to survive assurance.

The conclusion most ESG leads reach is that on-site solar is the only lever that improves the location-based figure — the number that cannot be argued with — while also reducing energy spend rather than adding to it. A green tariff makes the market-based line look good but leaves the physical footprint untouched; on-site solar moves both. Pair it with battery storage to lift self-consumption further, and model the economics on our commercial solar cost page and across the four finance routes.

Office Scope 2 reduction case study: measured tonnes avoided

To show the figures in context, here is a representative outcome for a 280 kWp installation on a four-storey city-centre office of around 4,500 m² with a typical 9-5 occupancy profile. The numbers below are the kind that appear in the customer's SECR statement and CDP response the following year.

Because the office demand peak (HVAC, lighting and IT through the working day) coincides with peak solar generation, self-consumption is high — which is exactly what maximises both the Scope 2 reduction and the bill saving. The avoided emissions are metered and traceable, so they survive third-party assurance without the additionality questions that dog certificate-based claims. Explore more office solar case studies or read how landlords and tenants split the benefit on multi-let buildings in our landlord and tenant guide.

Estimating your own Scope 2 reduction

The arithmetic scales linearly: annual generation × self-consumption % × the DEFRA factor for the year gives the tonnes of CO₂e you avoid. As a rule of thumb for UK offices, every 100 kWp of well-sited rooftop solar generates roughly 92,000 kWh/year; at 75% self-consumption and the 2024 factor that is about 14-15 tonnes CO₂e avoided per 100 kWp. To model your specific roof, floor area and daytime load, use our commercial solar cost and payback calculator — it sizes the system and returns generation, saving and payback, which feed straight into the Scope 2 sums above. Estates and facilities teams managing a portfolio should also see our estates and facilities managers guide for roll-out across multiple buildings, and our MEES 2030 guide for how the same install lifts the EPC band.

The wider UK regulatory stack and your money pages

Scope 2 reporting does not sit in isolation. The same solar install that cuts your reported emissions also lifts the building's EPC band toward the MEES 2030 EPC B requirement for commercial lets, qualifies for the Annual Investment Allowance and other finance routes, and earns export revenue under the Smart Export Guarantee. Sector teams with their own reporting nuances can read our pages for financial-services offices and law firms, and any project can start with our 7-day desk feasibility process.

The Scope 2 Disclosure Pack we provide

Every commercial office solar installation we deliver includes a Scope 2 Disclosure Pack on commissioning. The pack contains:

1. Location-based and market-based Scope 2 emissions calculations with year-specific DEFRA conversion factors and citation references
2. REGO certificate handling explanation (whether REGO-certified, whether surrendered under SEG, or claimed on physical traceability)
3. Annual kWh generation evidence from system monitoring (with monthly resolution and string-level data on request)
4. SECR-ready narrative text suitable for inclusion in the annual report
5. CDP Climate Change response text pre-populated for sections C6, C8, C9
6. TCFD disclosure mapping across Governance, Strategy, Risk, Metrics and Targets
7. SBTi pathway alignment statement and PPN 06/21 Carbon Reduction Plan input data (where applicable)

The pack is updated annually on request to reflect changing DEFRA conversion factors and updated generation data, at no additional cost during the warranty period.

TCFD, CDP and SBTi: how solar reads across each framework

TCFD-aligned disclosure has four pillars — Governance (board-level capex sign-off on net-zero programmes), Strategy (transition opportunities and an electricity-price hedge), Risk Management (price and MEES regulatory risk reduced), and Metrics and Targets (Scope 2 reduction and renewable percentage). On-site solar features in all four.

CDP's Climate Change questionnaire credits documented renewable electricity programmes in sections C6 (emissions data), C8 (energy, including renewable percentage) and C9 (additional metrics and low-carbon investment). Companies moving from C/D to A/A- scores typically need both renewable electricity coverage — often solar — and validated targets.

The Science Based Targets initiative requires 1.5°C-aligned near-term targets (commonly around -42% absolute Scope 1+2 by 2030 from a recent baseline) and net zero by 2050. For most office occupiers, hitting 2030 SBTi targets is impossible without renewable electricity coverage, and on-site solar is usually the cheapest single contribution to it.