Voltage optimisation: where it shines and where it doesn't

Voltage optimisation is not a silver bullet, but when applied to the right mix of assets it delivers a measurable reduction in energy cost and carbon intensity without compromising performance. The core thesis is simple: optimise the supply voltage to match the actual demand of your plant, and you can eliminate unnecessary reactive power and resistive losses – a proven lever for UK commercial sites that already benefit from TUS Group’s broader flex‑management portfolio.

Why voltage optimisation matters

The UK electricity network is designed to operate at a nominal 230 V (phase‑to‑neutral) for most commercial customers. In practice, supply voltages often sit 5‑10 % above this level, especially during low‑load periods. That excess voltage forces every resistive load – from motor windings to fluorescent ballasts – to draw more current than required, increasing I²R losses and raising the demand charge on your TNUoS and DUoS bills.

Under the Streamlined Energy and Carbon Reporting (SECR) framework, UK businesses must disclose energy efficiency actions and associated savings. Voltage optimisation provides a straightforward, low‑capital‑expenditure measure that can be quantified, reported, and verified – a valuable piece of the SECR puzzle and a way to demonstrate progress against the Climate Change Levy (CCL) and the Carbon Budgets set by the Department for Energy Security and Net Zero (DESNZ).

Where it delivers fast returns

Motor‑intensive plants

Industrial sites with large motor fleets – food processing, packaging, and automotive component manufacturers – typically run motors at or near full load for long periods. Motors are sensitive to supply voltage; a 5 % reduction in voltage can cut motor current by up to 10 % without loss of torque, translating into a 5‑12 % reduction in electricity consumption. For a 5 MW motor‑driven facility, a conservative 7 % saving equates to roughly 300 MWh per year, or £30,000 in avoided electricity costs at £0.10 kWh⁻¹. At a typical optimisation system cost of £15‑£20 kW, the payback falls within the 2‑3 year window.

Legacy lighting and fluorescent ballast loads

Older commercial premises still rely on fluorescent lighting and magnetic ballasts, which are inherently voltage‑sensitive. Reducing supply voltage by 5‑8 % can lower ballast current by 10‑15 %, delivering a 5‑10 % saving on lighting electricity. A 10,000 m² office building with a 250 kW lighting load would therefore save around 12 MWh annually – roughly £1,200 – against an optimisation installation cost of £5‑£7 kW, again delivering a sub‑3‑year payback.

Older electrical assets and transformer‑linked sites

Sites with ageing cabling, legacy transformers, or a high proportion of resistive heating (e.g., hot‑water boilers) experience amplified I²R losses when supplied at higher voltages. Voltage optimisation reduces line losses by up to 15 % in such contexts. For a site drawing 2 MW continuously, the loss reduction can save 260 MWh per year, equating to £26,000, comfortably covering the typical system cost of £10‑£12 kW.

When the economics fall short

Modern LED and VFD environments

LED luminaires and variable‑frequency drives (VFDs) already incorporate power‑factor correction and internal voltage regulation. The marginal benefit of external optimisation drops to under 2 %, often insufficient to meet a 2‑year payback. In a 500 kW office with full LED retrofit, the expected saving is less than 5 MWh per year – roughly £500 – which would require a system cost below £2 kW to be viable, an unlikely scenario.

Small, low‑load sites

Retail units or small service businesses with peak demand under 100 kW see limited absolute savings. Even a 10 % reduction yields only a few megawatt‑hours annually, making the capital outlay hard to justify unless the optimisation hardware is bundled with other services such as demand‑side response (DSR) or the TUS Yolk portal, where the free switching analysis can add ancillary value.

Calculating the payback

Example 1 – 3 MW food‑processing plant

• Baseline electricity use: 3 MW × 8 000 h = 24 000 MWh/yr
• Expected optimisation saving: 8 % → 1 920 MWh/yr
• Annual cost avoidance (£0.10/kWh): £192 000
• Optimisation system cost (incl. installation): £30 kW × £20 = £600 000
• Payback: £600 k / £192 k ≈ 3.1 years (improved to 2.5 years when combined with TUS flex‑management, which already delivers 150 + GWh under flex management and beats supplier forecasts by 20 %).

Example 2 – 250 kW office with fluorescent lighting

• Baseline use: 250 kW × 3 500 h = 875 MWh/yr
• Expected saving: 9 % → 79 MWh/yr
• Annual cost avoidance: £7 900
• System cost: £5 kW × £18 = £90 000
• Payback: £90 k / £7.9 k ≈ 11.4 years – not viable alone, but when paired with the Yolk portal’s average 27 % switching saving, the combined effect can reduce the overall energy bill by an additional £15 k, bringing the effective payback to just over 5 years.

Implementation considerations

Choosing a provider

A credible provider must demonstrate a track record – TUS Group currently manages over 150 GWh under flex management and operates a 30‑plus supplier panel, giving it the data depth to model voltage optimisation accurately. Look for third‑party verification, preferably through an accredited testing body such as the Energy Institute (EI) or an Ofgem‑approved scheme.

Integration with flex management and the Yolk portal

Voltage optimisation works best when combined with real‑time demand response. TUS’s flex‑management platform can curtail load during peak periods, while the Yolk portal offers a free, data‑driven switching service that has delivered an average 27 % saving for clients switching suppliers. The synergy reduces overall demand, improves the utilisation of the optimisation hardware, and shortens the payback horizon.

Compliance and reporting

Ensure the optimisation scheme is registered with Ofgem’s Metering and Data Management (MDM) system if you intend to claim any ancillary service payments. Record the voltage reduction settings and the resulting kWh savings for SECR reporting, and update your CCL exposure calculations accordingly. The system should also log voltage excursions to satisfy NESO’s network performance monitoring requirements.

Bottom line

Voltage optimisation delivers a reliable 5‑15 % reduction in electricity use for UK commercial sites that have motor‑heavy, fluorescent, or ageing electrical assets, typically achieving a 2‑3 year payback. The economics deteriorate for modern LED‑only or low‑load premises, where the savings rarely exceed 2 %. When paired with TUS’s flex‑management and the free Yolk switching portal, even marginal sites can improve their overall energy economics. A disciplined, data‑driven approach – backed by proven UK regulatory frameworks – ensures the investment is defensible, measurable, and aligned with corporate sustainability targets.