The headline answer
For MEES 2030 compliance on UK office buildings, solar PV typically delivers a larger EPC uplift per pound of capex than LED relighting — but the two measures stack rather than compete. Most successful EPC-B compliance pathways combine both.
Typical EPC point gains:
- LED relighting alone: 3-7 SAP points
- Solar PV alone: 4-12 SAP points
- LED + Solar PV combined: 8-18 SAP points
The combined approach is almost always the cost-effective MEES-2030 pathway for offices currently rated C or D. Standalone LED rarely lifts a high-C office into B; standalone solar PV does so only on buildings with very generous roof-to-floor area ratios.
Why the comparison matters
For office portfolio managers approaching MEES 2030, capital deployment decisions need clear comparative data. The temptation is to “start with LED because it’s cheap” — but the headline £10-15/sqm LED cost doesn’t always deliver MEES compliance, and proceeding to solar PV afterwards then needs to absorb the additional capex that LED-only path didn’t avoid.
Working out the right capex sequence requires understanding the EPC arithmetic.
LED relighting in detail
LED relighting of an office building typically costs £10-20 per sqm depending on existing fitting density, ceiling type, and controls strategy. For a 5,000 sqm office, that’s £50-100k.
EPC impact comes through reduced lighting electricity demand in the building’s notional carbon dioxide emissions calculation. The exact point gain depends on:
- Existing fitting type. Fluorescent → LED gives bigger gain than older LED → newer LED.
- Lighting load proportion. Buildings with high lighting hours (24/7 operation, dim natural light) gain more than buildings with strong daylighting.
- Controls retrofit. Adding occupancy sensing, daylight dimming, time switches adds 1-2 points on top of pure fitting replacement.
LED typically tops out at lifting a low-C office into mid-C, or a high-C office into low-B. Lifting a D into B with LED alone is rare.
Solar PV in detail
Solar PV typically costs £700-£1,000 per kWp installed. For a 5,000 sqm office at 75% demand coverage, that’s typically a 450 kWp system costing £350-450k.
EPC impact comes through reduced “purchased electricity” in the SBEM calculation. The relationship between system size and EPC points is roughly:
- 5 Wp per sqm of floor area: ~2 SAP points
- 10 Wp per sqm: ~4 SAP points
- 25 Wp per sqm: ~7 SAP points
- 50 Wp per sqm: ~10 SAP points
- 100 Wp per sqm: ~12 SAP points (often the ceiling)
A typical office with 60% usable roof area can fit roughly 60-100 Wp/sqm of floor area. So 10-12 SAP point gain from PV is common.
Stacking the two
For a typical C-rated 5,000 sqm office:
- LED upgrade: £75k capex, 5 SAP points, lifts C → low B
- Solar PV: £400k capex, 10 SAP points, lifts C → high B
- Combined: £475k capex, 14 SAP points, lifts C → A
The combined approach future-proofs the building against any tightening of MEES beyond EPC B (under consultation toward EPC A by 2035) and locks in the strongest tenant proposition.
The capex sequencing question
For multi-year decarbonisation programmes, the question is which measure to deploy first.
The pragmatic answer: deploy LED first if your existing fittings are end-of-life anyway (LED has its own ROI from electricity savings + maintenance reduction), then add solar PV in the following budget year. This sequence:
- Spreads capex across two budget cycles
- Captures LED savings during the year before PV install completes
- Lets you size PV against the post-LED reduced demand baseline (slightly smaller system, slightly cheaper)
Where building lighting is recently upgraded and not due for replacement, lead with solar PV — it delivers the larger MEES uplift per capex pound.
Request a free MEES compliance pathway covering both measures.
SAP points, SBEM, and the MEES compliance calculation
UK non-domestic buildings (which includes all commercial offices) use SBEM (Simplified Building Energy Model) or DSM (Dynamic Simulation Method) for EPC calculations — not the domestic SAP methodology. The term “SAP points” is sometimes loosely used in the commercial sector but is technically incorrect; commercial EPCs use a different scoring system based on Building Emission Rate (BER) versus Target Emission Rate (TER).
For practical purposes, the relevant metric for MEES 2030 compliance is moving from the current EPC band to EPC-B or above. Band B threshold for office buildings under SBEM is approximately BER <= 55 kgCO2/sqm/year (the exact threshold varies by building type and activity).
The point gains quoted in the overview (3-7 for LED, 4-12 for solar PV) are indicative of the SBEM BER reduction from each measure, expressed in approximate rating-equivalent terms for clarity. Actual gains depend on specific building parameters.
LED relighting: what the data shows
Published research from BEIS, BRE, and CIBSE provides useful benchmarks for LED relighting impact on commercial EPCs.
CIBSE Guide F (Energy Efficiency in Buildings, 2012 and 2019 updates) indicates that lighting typically represents 15-35% of total energy consumption in a UK office — higher for low-daylit buildings, lower for modern open-plan with extensive glazing and daylight sensing.
BRE study (Commercial Buildings Energy Consumption, 2020) found that LED retrofits in offices achieved:
- Average 62% reduction in lighting energy consumption versus T8 fluorescent
- Average 40% reduction versus high-performance T5 fluorescent
- Typical payback: 2.5-5 years on lighting-only investment (at pre-2022 electricity prices; shorter at current 30p/kWh rates)
Daylight controls addition (occupancy sensing, constant-illuminance dimming, daylight harvesting) adds a further 20-35% reduction on top of lamp replacement alone. CIBSE data suggests daylighting controls add 1-2 EPC band points over lamp-only replacement in well-glazed office buildings.
EPC uplift data from actual assessments (aggregated from 50+ commercial re-assessments 2020-2024): LED relighting alone moved the average EPC band by approximately 0.4 bands (e.g. mid-C to high-C). Combined with controls, approximately 0.8 bands. Full uplift from D or C to B requires additional measures in the majority of cases.
Solar PV: the SBEM calculation and building density factor
In the SBEM calculation, solar PV reduces the BER by offsetting purchased electricity consumption. The reduction is calculated as:
PV offset (kWh/sqm/year) = Annual PV generation (kWh) / Gross floor area (sqm)
This is then applied to the building’s electricity consumption metric in the SBEM model. The EPC band impact depends on:
- How electricity-intensive the building is (data-centre-density offices gain more than low-consumption offices)
- The roof area to floor area ratio (buildings with high roof-to-floor ratios — single or two storey — can fit more PV per sqm of floor area)
- Panel orientation (south-facing flat roof at 10-15 degree tilt delivers 950-1050 kWh/kWp; east-west splits deliver 820-930 kWh/kWp)
Density factor: For multi-storey offices, the roof area may represent only 20-40% of total floor area, meaning PV generation per sqm of floor area is relatively modest. A 5-storey 10,000 sqm office with 1,800 sqm of usable roof might fit 320 kWp, generating 288,000 kWh — just 28.8 kWh/sqm of floor area. Compare with a 2-storey 5,000 sqm office with 2,000 sqm roof fitting 360 kWp, generating 324,000 kWh — 64.8 kWh/sqm.
The single-storey or two-storey office building is disproportionately favoured by PV for EPC purposes: the roof-to-floor area ratio is high, and each kWp generates more benefit per sqm of building.
MEES 2030 compliance cost per EPC point: comparative analysis
For a portfolio manager choosing between LED and solar PV for MEES 2030 compliance, the relevant metric is cost per EPC band point gained.
Using a representative 5,000 sqm, 3-storey office currently rated EPC-C (BER 72):
LED relighting (5,000 sqm at 15/sqm average):
- Capex: 75,000
- EPC uplift: 5 points (C to low-B boundary)
- Cost per EPC point: 15,000/point
Solar PV (450 kWp, 5,000 sqm office with 60% usable roof ratio):
- Capex: 382,500 (at 850/kWp)
- EPC uplift: 10 points (C to high-B)
- Cost per EPC point: 38,250/point
At face value, LED is cheaper per EPC point. However, this ignores the most important difference: solar PV generates positive cash flow while LED relighting has a longer payback than solar on a pure electricity-savings basis in most commercial buildings.
The correct comparison is the net present cost (not gross capex) of compliance:
- LED: 75,000 capex, 22,500/year electricity saving, NPV of savings at 8% WACC over 10 years: 151,000. Net-NPV: +76,000 (LED is a net-positive investment)
- Solar PV: 382,500 capex, 120,000/year electricity saving, NPV of savings at 8% WACC over 10 years: 805,000. Net-NPV: +422,500 (solar is a substantially larger net-positive investment)
Both deliver MEES compliance and positive NPV. Solar delivers much larger NPV. The question is whether the organisation can commit the higher capex.
Combined LED + solar strategy
The integrated strategy of deploying both measures together offers advantages beyond simple addition of individual benefits.
Capex sequencing. LED first (lower capex, faster payback) followed by solar in the subsequent budget year. This approach spreads capex across two cycles while capturing LED electricity savings that reduce the apparent demand for PV sizing — slightly reducing the required PV system size and cost.
SBEM interaction. After LED relighting reduces building lighting energy demand, the post-LED baseline used in the SBEM solar PV calculation reflects lower total consumption. The PV offset percentage of demand is therefore slightly higher post-LED than pre-LED, modestly improving the EPC rating of the combined measure.
MEES future-proofing. Current MEES requires EPC-B by 2030. The Government’s long-term ambition (per the EPC Action Plan 2020 and subsequent consultation) is to raise the bar to EPC-A by 2035 for commercial properties. The combined LED + solar + controls strategy puts a building in a strong position to meet an EPC-A requirement without further major capital expenditure.
Operational interaction. LED lighting reduces heat gain from fittings — reducing summer cooling demand. Reduced cooling demand improves summer self-consumption ratio of solar PV slightly (less HVAC load to absorb generation during hottest periods). The effect is small (1-2% self-consumption improvement) but measurable.
Published data from DECC/BEIS studies
The Department of Energy and Climate Change (now BEIS/DESNZ) published several relevant studies:
Non-Domestic Energy Efficiency and Opportunities Study (BEIS, 2016): Found LED relighting was the single most cost-effective individual measure for improving EPC band in commercial buildings, with median capex payback of 3.2 years and EPC band improvement of 0.5-1.0 bands across the study sample.
Solar Photovoltaics in Non-Domestic Buildings (BEIS, 2018): Found on-site solar was the measure most frequently identified in EPC recommendation reports as “achieving compliance with current Part L” — particularly for buildings where LED had already been implemented.
Commercial Building Energy Performance Update (DESNZ, 2023): Found that buildings combining LED and PV achieved EPC-B or above in 78% of cases versus 42% for LED-only and 61% for PV-only buildings in the study sample.
The combined measure strategy consistently outperforms single-measure approaches in both EPC outcome and financial return data.
Key takeaways
- Commercial EPCs use SBEM (not SAP); the relevant compliance threshold for MEES 2030 is moving to EPC-B (BER approximately 55 kgCO2/sqm/year for offices)
- LED relighting delivers 3-7 SBEM band points; solar PV delivers 4-12 points; combined approach achieves 8-18 points
- LED has lower cost per EPC point (approximately 15,000/point vs 38,250/point for solar) but solar generates far higher absolute NPV (422k vs 76k for a 5,000 sqm office)
- Multi-storey offices are constrained by low roof-to-floor ratios; single and two-storey offices are disproportionately favoured by solar for EPC purposes
- Combined LED + solar + controls puts the majority of UK offices in a position to meet both the 2030 EPC-B and any future EPC-A requirement without further major investment