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Looking to cut electricity use as prices rise and environmental awareness grows? One option attracting attention is voltage optimisation (VO): a device that reduces and stabilises the voltage supplied to your home. This report explains VO in plain terms and reviews a real-world installation of an EnergyAce 100A unit fitted on 19 November 2022, using actual EDF Energy meter data (2020–2024) to assess its impact.
Context
Before installation, this home used unusually high amounts of electricity after replacing gas radiators with electric heaters in 2020. Unit rates rose from about 14.55p/kWh in 2020 to around 34p/kWh in 2022, sharply increasing bills. No major changes to appliances or heating were made around the VO installation date, so before/after comparisons are meaningful.
What is a voltage optimiser?
A VO unit is a specialised transformer/regulator installed between the meter and consumer unit. UK mains is typically ~240 V and can legally reach ~253 V, while most appliances are designed around 230 V. A VO trims the excess so your home runs closer to 220–230 V. Many household loads are voltage-dependent (for example, resistive heaters, towel rails, heated mirrors, some legacy appliances). Lowering voltage reduces their power draw and heat losses, often without noticeable performance changes. It can also reduce stress on equipment and extend service life. Units may offer fixed voltage drops (e.g. –10/–15/–20/–25 V) or auto-regulated outputs.
Manufacturers typically claim savings of 5–20% depending on incoming voltage and load mix. EnergyAce advertises “up to 20%” and guarantees a minimum 10% kWh reduction or refunds the unit cost.
The EnergyAce 100A installation
The homeowner selected the EnergyAce Compact 100A (single-phase, whole-house up to 100 A). A qualified electrician installed it in about three hours, inline between meter and consumer unit. Initial testing tried a –25 V tap (observed ~211 V), then settled on –20 V (~216 V) to remain within the recommended lower limit. No other system changes were made.
Why this device?
With projected annual use near 18,000 kWh in 2022, a 10% saving would be ~1,800 kWh/year. At 34p/kWh that’s roughly £612/year (about £270/year at 15p/kWh). EnergyAce’s domestic calculator estimated ~£539/year saving at 34p/kWh for this home. The 10% guarantee and five-year warranty helped de-risk the choice.
Electricity use 2020–2024
From 2020 to 2022, use remained high, peaking at 17,862 kWh in 2022. After VO installation (Nov 2022), consumption fell to 15,102 kWh in 2023 and 14,767 kWh in 2024. That’s about a 17% reduction relative to 2022, exceeding the guaranteed 10%.
Did VO actually save energy?
The data indicates yes. In 2023, usage was about 2,760 kWh lower than 2022. At an average 28p/kWh, that equates to ~£772.80 saved in 2023.
Why might savings be this strong?
• Voltage-dependent loads: Simple resistive devices (towel rails, older heaters) draw less power at lower voltage.
• Thermostatic loads: Some appliances (ovens, immersion heaters) take slightly longer to reach temperature; total energy to reach set-point may be similar, but reduced peak power can avoid overshoot and cycling losses in real-world use.
• Electronics: Modern switch-mode devices (TVs, chargers, laptops) draw near-constant power; VO has little impact on their kWh, though it may reduce internal heating and provide gentler operation.
• Motors: Effects vary by loading and control method; many modern appliances use electronically controlled motors, so savings are modest here.
This home already had LED lighting, so the most likely drivers were the numerous resistive heaters (ten 1.5 kW units—15 kW total). In such a load profile, VO can have a marked effect.
Independent checks with EDF bills
EDF bills support the change in usage pattern. A July 2022 bill (pre-VO) listed estimated annual electricity consumption at ~16,879 kWh. A July 2023 bill (post-VO) showed ~15,188 kWh. Year-on-year meter readings corroborate the broader ~17% reduction observed in full-year totals.
Costs, savings, and payback
Based on 2023 consumption, the device saved ~2,760 kWh (~£772.80 at 28p/kWh). With an installed cost of £829.99, payback was just over one year (≈1.07 years), faster than the calculator’s initial projection of ~1.54 years.
Nuance and limitations
VO is not a cure-all. Homes with lower incoming voltage, predominantly voltage-independent loads, or already efficient electrics may see smaller savings. Some independent studies have reported modest benefits in typical households. The technology performs best where voltage is consistently high and the load mix includes significant voltage-dependent demand (as in this case).
Environmental impact
Cutting ~3,000 kWh/year typically reduces CO₂ emissions by roughly 0.7–1 tonne/year, depending on the grid mix—an additional benefit alongside the bill savings.
Key takeaways for homeowners
• Suitability matters: Expect larger savings if your supply sits high (240 V+) and you use significant resistive heating or other voltage-dependent loads.
• Track your data: Compare annual kWh from bills before and after installation to verify results.
• Do the maths: As a rule of thumb, 10% of your annual kWh × your unit rate ≈ expected annual saving. If that figure is small, payback may be long.
• Side benefits: VO can smooth over-voltage, reduce equipment stress and heat, and operate silently in the background.
• Complementary measures: VO fits alongside insulation upgrades, efficient appliances, smart controls, and behavioural tweaks.
Conclusion
For this high-consumption household, the EnergyAce 100A voltage optimiser delivered a clear, data-backed reduction in electricity use—about 17% in the first full year—beating the manufacturer’s 10% guarantee and paying back in just over a year. VO won’t deliver identical results everywhere, but where conditions are right it can be a practical, set-and-forget addition to an energy-saving toolkit, lowering bills and carbon without affecting comfort or routine.
For more information on Voltage Optimisation in the Home: A Case Study with the EnergyAce talk to Expert Electrical Supplies Ltd