Another use for BPL is regulating public lighting.

With climate change and global warming the topic du jour, Schneider's Hadrian said his company has approached local councils to try and implement new energy-saving lighting systems that are based on BPL equipment.

One of Schneider's products, called the Lubio, can regulate the voltage applied to the lights for the majority of their operating time. He said it can be set up to work with photoelectric detectors - which are used to control the lights - in several ways.

"Lights generally need close to the full nominal voltage to start and stabilize. The Lubio ensures that full voltage is available for the first 10 to 30 minutes or so and then reduces the voltage. There is a slight reduction in light output but it is generally imperceptible. However, the energy saved is significant: 30 to 40 per cent," he said.

Alternatively, the voltage available from the network transformers also varies depending on the load on the electricity network.