Are voltage optimisers worth it?

Helpful video reference. This guide draws on Jordan Farley's Artisan Electrics short "Think Twice Before Installing A Voltage Optimiser". Jordan is a qualified UK electrician and managing director of Artisan Electrics, a Cambridge-based firm with over 375,000 YouTube subscribers. His take on voltage optimisers is exactly the kind of sceptical, evidence-based view that saves homeowners money.

1. What a voltage optimiser does

A voltage optimiser sits between the incoming mains supply and your consumer unit. It uses a transformer to reduce the incoming voltage, typically from around 240-245V down to around 220-225V. The theory is that most UK electrical appliances were designed for 220V (the European standard that harmonised with the UK's old 240V nominal in 1995), so reducing to 220V allows them to run at their design voltage rather than slightly above it.

For resistive loads - anything with a simple heating element like a kettle, toaster, or old-style immersion heater - lower voltage means lower power consumption and lower energy use. If your kettle normally runs at 245V and you drop it to 220V, it will take a few extra seconds to boil but use slightly less electricity in doing so.

2. What the UK grid voltage actually is

The marketing for voltage optimisers often assumes UK homes receive 240V or higher. That used to be more reliable than it is today. The UK harmonised its nominal voltage to 230V in 1995, and grid management has gradually brought average delivered voltages down. The legal range is 230V +10%/-6%, meaning anywhere between 216V and 253V is within spec.

Measure your own incoming voltage with a multimeter at a socket. You may find it is already at 230V or below, particularly if you are in an urban area or on a newer part of the distribution network. If your incoming voltage is already at 225V, a voltage optimiser cannot reduce it by another 20V without going outside safe limits.

Many rural properties, older housing estates, and homes at the end of a long cable run may receive higher voltages - sometimes over 245V consistently. Those homes have more to gain from optimisation. If you are in a new build or a recently rewired property in a well-maintained urban grid, check before assuming you have a problem.

3. Which loads respond and which do not

This is where the headline savings figures break down. The energy savings from lower voltage only apply to resistive loads, and the list is shorter than most marketing suggests:

• Resistive loads that benefit: kettles, toasters, electric showers (to a small extent), old incandescent bulbs (now rare), and resistive storage heaters without thermostatic control.
• Loads that do not benefit: LED lighting (switch-mode drivers regulate to constant brightness regardless of input voltage), EV chargers (power electronics regulate themselves), heat pumps (compressor motor speed varies but efficiency is not straightforwardly improved), modern televisions and computers (switch-mode power supplies), and any appliance with a thermostat (it just runs for longer to reach the same temperature).

In a typical 2026 UK home - LED lighting throughout, a modern boiler or heat pump, a smart TV, and perhaps an EV charger - the fraction of electricity use that genuinely benefits from lower voltage is small. The immersion heater in the hot water cylinder is often the largest resistive load left, but if it has a thermostat it will compensate for the lower power by running longer.

4. The honest payback calculation

Take a realistic example: a home using 3,500 kWh per year, paying 24p/kWh, with 15% of consumption from resistive loads (unusually high for a modern home). A 5% reduction in consumption from those loads gives a saving of 3,500 × 0.15 × 0.05 = 26 kWh per year, or about £6.20. Even tripling that estimate for optimism gets to £20 per year.

A quality voltage optimiser (Powerstar, Powervar or similar) with professional supply and installation costs £400-800. At £500 installed and £20 per year saving, payback is 25 years. Most manufacturers quote a 10-15 year device life.

Some suppliers quote 10-15% whole-home savings. Those figures come from studies done in homes with high resistive loads and high incoming voltages, often commercial or older residential properties. They are not representative of a modern home.

5. When a voltage optimiser does make sense

There are situations where the calculation changes:

• Consistently high incoming voltage. If your measured voltage is regularly above 245V, you have more headroom to optimise and the savings are more meaningful.
• High resistive load. An older property with a primarily resistive heating system, an old immersion heater without a good thermostat, and little LED penetration has a bigger pool of loads that respond.
• Three-phase commercial supply. The business case in small commercial settings can be stronger than in domestic homes, with higher resistive loads and more consistent over-voltage.
• Appliance lifespan. Some evidence suggests running equipment at slightly lower voltage extends motor and component life. This is harder to quantify but is a legitimate consideration for equipment with high replacement cost.

6. What to spend the money on instead

For most UK homes, the same £500 spent elsewhere delivers a much better return:

• Loft insulation top-up to 270mm (if you have access) - often free or subsidised under ECO4.
• Replacing any remaining halogen bulbs with LED.
• A smart thermostat if you do not have one.
• An energy monitor to identify actual high-consuming appliances.
• Draught-proofing doors, letterboxes and loft hatches.

Each of those will outperform a voltage optimiser in a typical modern home.

When to call us

If you have been quoted for a voltage optimiser and want a second opinion on whether it suits your property, Richard can measure your incoming voltage and give you an honest view. For properties in east Kent with consistently high incoming voltage and suitable load profiles, the case can be made. For most modern homes, we would point you somewhere more productive.