More people are opting to take on fixed price electricity contracts to avoid the uncertainty of price hikes.

Mighty River Power says the proportion of Mercury Energy residential customers on fixed-price contracts increased to 43 percent during the three months to March.

More than 28,000 customers took up a two-year offer.

The company said national demand for electricity rose to the highest level on record for the third quarter.

It's up half a percent compared to the same period last year.

Mighty River Power will release its financial results for the 12 months to June 2016 on August 23rd.