Lines company Unison is increasing charges from today for households generating their own electricity, typically solar generation.

Unison manager of business assurance Nathan Strong said it was to make sure they paid their fair share - they payed less because of lower electricity volumes yet they still used the network.

"Unison must build and maintain a network to support the delivery of electricity at peak demand, which is during the winter evenings - a time when most distributed generation systems, such as solar panels, are not helping to reduce the network peak," he said.