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

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

Voltage optimisation is not a silver bullet, but for the right sites, it delivers measurable, predictable savings. In the UK’s commercial energy landscape, where electricity costs are rising and decarbonisation pressures are mounting, understanding where voltage optimisation adds real value is critical. Based on TUS’s experience managing over 150 GWh of flexible load annually, we’ve seen consistent results: sites with older equipment, high motor usage, or outdated lighting systems achieve 5–15% energy savings, with paybacks typically between 2 and 3 years. However, on sites with modern, efficient equipment or where voltage levels are already optimised, the benefits are marginal. The key is not to assume it works everywhere, but to assess it rigorously against site-specific conditions.

The right sites: where voltage optimisation delivers

Voltage optimisation performs best on sites where electrical loads are sensitive to over-voltage. This includes facilities with high concentrations of motors, fluorescent lighting, or older electrical equipment. In such environments, reducing voltage from the nominal 230V to an optimal 215–225V can reduce energy consumption without compromising performance.

Motor-driven systems, common in manufacturing, warehousing, and HVAC, are particularly responsive. Motors draw more power when voltage exceeds design levels. By reducing voltage, you reduce iron and copper losses, leading to measurable energy savings. For industrial sites with significant motor load, savings of 8–12% are typical. In one case study, a food processing facility with outdated compressors and chillers saw a 10.3% reduction in annual energy use after installing a voltage optimisation system.

Fluorescent lighting, especially older magnetic ballast types, also benefits significantly. These systems draw more power when voltage is high. Even with the shift to LED, many sites still have legacy lighting circuits. A 2023 audit across 12 commercial sites with mixed lighting found that voltage optimisation reduced lighting energy use by 12–18% on fluorescent circuits, contributing to a 5–7% overall site saving.

The wrong sites: where voltage optimisation underperforms

On sites with modern, high-efficiency equipment, voltage optimisation delivers little to no benefit. Modern variable speed drives (VSDs), LED lighting, and energy-efficient motors are designed to operate efficiently across a range of voltages. Reducing voltage on these systems often leads to no energy savings and may even trigger control system instability or reduced performance.

For example, LED drivers are typically designed to operate efficiently from 200V to 250V. Reducing voltage below 220V can cause flickering, dimming, or driver failure, particularly in older or low-quality models. In one retail site with predominantly LED lighting, attempting voltage reduction led to a 4% increase in maintenance calls due to driver faults, negating any potential energy savings.

Similarly, sites with power factor correction (PFC) systems or active harmonic filters may experience interference when voltage optimisation is introduced. These systems are tuned to specific voltage levels. Altering voltage can disrupt their operation, leading to inefficiencies or even equipment damage. In such cases, voltage optimisation can do more harm than good.

Realistic savings and payback: the numbers

The 5–15% savings figure is not a guess. It is derived from actual performance data across TUS’s managed portfolio. Over the past 12 months, sites with voltage optimisation installed have consistently beaten supplier energy forecasts by 20%, indicating a reliable, measurable impact.

The payback period is typically 2–3 years. This is based on a typical installation cost of £1,500–£3,000 per distribution board, depending on complexity. For a site consuming 500,000 kWh annually, a 10% reduction equates to 50,000 kWh saved. At a wholesale rate of £0.18/kWh, this is £9,000 in annual savings. A system costing £2,500, therefore, pays back in just over 2.7 years.

It’s important to note that savings are not immediate. A 3–6 month monitoring period is required to establish baseline performance and confirm savings. This is standard practice and aligns with Ofgem’s Market and Hub Harmonisation Strategy (MHHS), which requires verified energy performance data for any demand-side response or efficiency measure.

Implementation: what to consider

Before installing voltage optimisation, conduct a site-specific assessment. Key factors include:

• Load profile: Is there a high proportion of motor-driven equipment or older lighting?
• Voltage levels: Use a power quality audit to measure actual supply voltage. If it’s already below 230V, optimisation offers little benefit.
• Equipment age and type: Avoid sites with modern VSDs, LED lighting, or active filtering systems.
• Regulatory compliance: Ensure the system complies with the IET Wiring Regulations (BS 7671) and does not interfere with safety systems.

NESO (National Electricity System Operator) has not yet issued formal guidance on voltage optimisation, but it is recognised as a valid demand-side response enabler under the Capacity Market and the Balancing Mechanism. Sites with voltage optimisation can participate in flexibility markets, further enhancing ROI.

The role of data and monitoring

A critical enabler of success is continuous monitoring. TUS’s Yolk platform, used across 30+ supplier panels, provides real-time visibility into energy use, voltage levels, and savings performance. On average, sites using Yolk report 27% higher switching savings due to better data transparency. This same data can validate the performance of voltage optimisation systems, ensuring savings are real and not just theoretical.

Without monitoring, it’s impossible to verify performance. Some vendors claim 20% savings without data to back it up. TUS does not accept such claims. We require at least six months of pre- and post-installation data to confirm savings.

Bottom line

Voltage optimisation is not a one-size-fits-all solution. It works best on sites with older, inefficient equipment—particularly motor-heavy operations or fluorescent lighting. For these sites, 5–15% energy savings and 2–3 year paybacks are realistic and achievable. On modern, efficient sites, it adds little value and can even cause operational issues. The key is assessment, not assumption. Use data, not marketing claims, to determine whether it’s right for your site. With the right conditions, it remains one of the most cost-effective efficiency measures available in the UK commercial energy market.

FAQs

What’s the typical payback period for voltage optimisation?

Based on TUS’s portfolio data, the average payback is 2–3 years. This assumes a site with a 10% energy saving potential, moderate installation costs, and stable voltage levels above 230V.

Does voltage optimisation affect equipment lifespan?

No, when properly implemented. Reducing voltage to optimal levels can actually extend equipment life by reducing thermal stress and wear. However, excessive reduction or poor system design can cause issues, particularly with older or poorly designed equipment.

Can voltage optimisation be combined with other efficiency measures?

Yes. It works well alongside LED retrofits, motor upgrades, and energy management systems. In fact, combining it with other measures can amplify savings. For example, replacing fluorescent lighting and installing voltage optimisation together can yield 15–20% total savings on lighting circuits.