Genesis Energy has been burning more coal at its Huntly power station than at any other time in the past five years

It's burned almost twice as much coal in the December quarter as in the same period a year earlier.

The company's blaming an unprecedented combination of lower than usual hydro-lake flows and reduced production from the Pohokura gas field.

Those shortages were compounded by planned maintenance at the Kupe gas production station and its gas-fired Huntly unit.