Kiwibank communications manager Bruce Thompson says while he can't release the figures, the short term promotion was extremely successful and there was temptation to keep going.
He says the special was done because interest rates were static for such a long time.
Thompson says Kiwibank thought it would start 2011 with something new and only do it for a short period because it wasn't related to the wholesale rates.
"We wanted to stir up the market and see what happened, particularly we were interested in new home buyers, those who had maturing loans with other banks, or money on variable loans with other banks.
"Because of its success, it is something we would consider again."
Kiwibank continues to offer a floating rate of 6.15%.