In the year to June 30 it had spent $3.8 million preparing for its proposed partial listing and has spent more since then and expects to spend $2.5 million a year on maintaining a presence on the NZX.
Chairwoman Joan Withers and chief executive Doug Heffernan would not comment on the partial listing, saying it was up to the Government, or forecast financial performance for the coming year because of pre-listing restrictions.
"We're not through the process yet. Obviously we've still got a way to go," Withers said.
The Government has said it will announce a decision next week on whether to go ahead with the sale, the first of up to five sales of minority stakes in state-owned energy companies and the national airline, Air New Zealand.
A Waitangi Tribunal report called on the Government to halt the process while a settlement is reached with Maori over claims to fresh water under the Treaty of Waitangi.
Retail sales volumes increased during the year by 5 per cent, largely due to a 14 per cent increase in sales to business customers, and a focus on high-value customer acquisition south of Auckland.
Heffernan said use of electricity by big industrial users had been declining for more than a decade.
Mighty River Power would not be affected more than any other supplier by the closure of part of Norske Skogg's Kawerau pulp and paper mill as it did not have a physical contract with the company, he said.
Smalley said the result was solid with "no nasty surprises".