Complete transparency on assumptions, calculation methods, corrections, and uncertainty underlying the economic projections presented throughout this website. Updated December 2025 to reflect verified current BESS benchmarks.
Material correction — December 2025: Previous versions of this website cited total system savings of £161–187bn and BESS savings of £121–134bn. These figures used pre-2025 BESS cost assumptions of £250–300/kWh, which have been superseded by dramatic cost reductions in 2024–2025. Revised figures using verified 2025 benchmarks are presented throughout this site. The correction was first acknowledged in our Fourth Formal Representation to DESNZ (02/03/2026). We are committed to accuracy over advocacy.
| Parameter | Value Used | Source / Notes |
|---|---|---|
| Solar Capacity Target | 45–47 GW | UK Solar Roadmap, DESNZ, June 2025 |
| Analysis Timeframe | 30 years (2025–2055) | Conservative — modern panels often exceed 30-year warranty |
| Pipeline Scale | 65+ GW total | REPD October 2025: 41.2 GW sub-NSIP + 24.7 GW NSIP-scale |
| VBPV Energy Premium (vs TMPV reference) | seasonal range 14.77%–24.52%; winter peak +24.52%. Note: TMPV monofacial baseline only — not directly comparable to TBPV. TBPV's bifacial rear-side gain is concentrated at midday, amplifying grid surplus and increasing BESS demand beyond TMPV figures. | Badran & Dhimish (2024), University of York — full year empirical. Note: measured vs tilted monofacial (TMPV) reference at 45°. TBPV's bifacial rear-side gain may reduce the net annual advantage vs TBPV while widening the winter seasonal advantage. |
| Duck Curve Reduction | 57% less severe | Derived from University of York generation profile comparison |
| Grid Hosting Capacity | +46% | Joutijärvi et al., Solar Energy, 262, 111819 (2023) |
| Agricultural Productivity | 80–90% maintained | Riaz et al. (2021), IEEE Journal of Photovoltaics; Next2Sun data |
| Scenario | BESS Required | Basis |
|---|---|---|
| TBPV (47 GW) | 170–190 GWh (TMPV reference baseline; TBPV bifacial rear-side gain will increase this figure) | Required to manage duck curve and provide evening peak supply. TBPV's bifacial rear-side gain deepens duck curve beyond monofacial reference. |
| VBPV (47 GW) | 78–87 GWh | 57% duck curve reduction vs TMPV reference → significantly less storage needed than TBPV |
| Storage avoided | ~92–103 GWh | TBPV requirement minus VBPV requirement (indicative — peer-reviewed TBPV-specific modelling not yet in published literature) |
| Source | BESS Cost (2025) | Date |
|---|---|---|
| BloombergNEF Energy Storage Cost Survey 2025 | $117/kWh global average turnkey | December 2025 |
| Ember — "How Cheap is Battery Storage?" | $125/kWh all-in utility-scale | October 2025 |
| Previous assumption (now superseded) | £250–300/kWh | Pre-2025 data — obsolete |
Avoided storage: 92–103 GWh
Unit cost (2025): $117–125/kWh ≈ £93–99/kWh (at £/$1.26)
Including replacement factor (30 years): ×1.0 (single installation at 2025 costs)
Result: (92–103 GWh) × (£93–99/kWh) = £8.6–10.2bn
Rounded to campaign figure: £9.5–10.5bn (conservative mid-range)
Why the figure fell so dramatically: The BESS market has experienced extraordinary cost reductions — a 40% fall in 2024 alone (BloombergNEF), with further falls in 2025. The $117/kWh 2025 figure is approximately 75% lower than the $500+/kWh assumption used in 2023-era analyses. The reduction in savings headline does not weaken the VBPV case — it reflects market reality and is more defensible to policymakers.
BESS figures caveat: The BESS requirement figures above (78–87 GWh for VBPV; 170–190 GWh baseline) are modelled against the tilted monofacial reference system (TMPV) used in the Badran & Dhimish (2024) and related studies. As TBPV (Tilted Bifacial PV) replaces TMPV as the UK industry default, TBPV's bifacial rear-side gain will increase the baseline BESS requirement above 170–190 GWh — further improving the relative BESS saving from VBPV deployment. Peer-reviewed TBPV-specific BESS modelling is not yet available in published literature.
Grid infrastructure savings derive from VBPV's 46% higher grid hosting capacity (Joutijärvi et al. 2023) and its superior demand alignment, which reduces the need for distribution network reinforcement, substation upgrades, and balancing services.
| Infrastructure Component | VBPV Saving (estimate) | Basis |
|---|---|---|
| Distribution network reinforcement deferral | £5–10bn | +46% hosting capacity → deferred DNO capex |
| Substation upgrade deferral | £3–7bn | Reduced peak loading from better demand alignment |
| Balancing services reduction | £2–4bn (over 30 years) | 57% less severe duck curve → less gas peaking, less curtailment |
| Transmission reinforcement | £4–5bn | Improved demand correlation reduces transmission constraint |
| Total grid savings estimate | £15–25bn | Conservative; independent verification needed |
Economic projections are inherently uncertain. The following caveats apply:
Independent Verification Encouraged. These projections represent our analysis of available research. We actively encourage independent verification by energy economics experts, peer review of methodology, and site-specific analysis for UK deployment locations. If you identify errors or have alternative methodological approaches, please contact the campaign.