Gas bills will rise by an average of 11 percent next month for Contact Energy customers, and 10 percent for Genesis customers - if not on fixed term contracts.
Electricity prices are also on the rise, by an average of 8 percent for Contact customers; Genesis does not yet have that figure available.
The size of the increases vary from customer to customer, and depend on where they live, and which plan they are on. One Contact Energy customer in Wellington has been notified of a 15 percent increase in their electricity price.
The companies have pointed to low gas production, and the increased cost of carbon credits, for rising gas prices.
However the four major generator-retailer companies; Contact, Genesis, Mercury and Meridian, have doubled their profits in the last 12 months from $788 million to more than $1.5 billion.
Kathryn speaks to Mike Fuge, the chief executive of Contact Energy and Paul Fuge, the manager of Powerswitch - Consumer NZ's price comparison website.