Mighty River Power plans to freeze its electricity and gas prices until April 2015. Its charges can make up to 60% of home electricity bills.
The commitment applies only to the company's standard charges and does not prevent the power generator from offering discounts and other special deals in particular areas or to specific groups of customers.
The price freeze also does not apply to the charges levied by lines companies or by national grid operator Transpower.
Consumer New Zealand chief executive Sue Chetwin said on Wednesday other generators will now be forced look at their own charges, and companies tend to react when big players hold or drop prices.
Ms Chetwin said it should be good news for consumers heading into winter.
Mighty River chief executive Doug Heffernan said the price freeze reflected his company's desire to retain its customers.
However, the company warned there are likely to be changes to bills in 2014 because of charges outside its control. They stem from transmission and distribution charges which are mostly regulated by the Commerce Commission.
