The Electricity Authority is not taking its investigation into high spot electricity prices in December last year any further after releasing a report on the causes.

Towards the end of November, wholesale spot prices began to increase and climbed rapidly throughout the first three weeks of December. The average price at the Haywards reference node for the first 22 days of December was $135.90 per MWh, up 144 per cent on the November average and 158 per cent on the average between December 1 and December 22 in 2009.

The authority released a report on the issue yesterday, which identified a number of factors including uncertainty about lake levels - which were at average levels, but were trending downwards - while inflows to hydro reservoirs were well below average levels.