Charges relate to promotion of unlimited broadband plan.
Trustpower is being taken to court by the Commerce Commission over the company's "good things happen when power and broadband get together" ads.
Seven charges have been laid against Trustpower under the Fair Trading Act. They relate to television, online and billboard ads run between March and July 2015 promoting Trustpower's unlimited data broadband offer.
The broadband plan was promoted as costing $49 a month for 12 months. However, the $49 price was only available to customers who signed up for power and broadband at the same address on a 24-month contract. After the first year, the cost of broadband was up to $79 a month. This was only disclosed in the fine print. If a customer wanted to cancel during the 24-month period they had to pay exit fees.
The commission said Trustpower had co-operated with the investigation and indicated it intended to plead guilty.