Limited potential

The reported VPhase voltage reduction device

is similar to many domestic embedded renewables technology — good technical performance but its potential may only be about 10 per cent realised.

Voltage reduction may indeed save energy but, over time, for only a small proportion of electricity consumed. Most domestic electricity performs heating and work duties and these energies will be expended regardless of voltage, controlled by thermostats (heating and cooling duties), or motor speed, controlled by frequency (domestic appliances). Some duties may require more time, but overall, the same energy in kWh will be expended.

This leaves lighting and electronic appliances. A 10 per cent voltage reduction will reduce incandescent light by 30 per cent and annoy householders, who will simply select higher wattage bulbs. The quantity of electronic devices, TVs, computers, hi-fis, will depend on the size and age of the household.

The greatest gains from VPhase will be in a house full of teenagers and thumping music and in these cases the head of household may well wish to adjust voltage to zero. Such households, however, have a benefit that, with full voltage, the heat given out by the electronic appliances reduces the cost of fossil fuel heating bills.

I suspect about 10-20 per cent of energy savings will apply to about 10 per cent of electricity consumed, giving an overall saving of 1-2 per cent before subtraction of the 1 per cent consumed by VPhase, and its carbon footprint from procurement of copper, Perspex, plastics, heavy wiring connections and installation activity. Regrettably, any savings are only on the lowest-priced part of one's quarterly bill.

The device will need to withstand temperatures of -10ºC to + 50ºC and be rigorously EMC compliant to avoid interference with possible electronic gas meters, such as Lattice ('Wireless Watch',10 March), especially if switching 50 amp loads.