The Garraways called police, who came and searched the lounge, but failed to turn up the mystery object.
"We heard a terrific crack and I thought it was the television. I didn't know what it was," Mr Garraway says.
As an ex-Army paratrooper, Mr Garraway knows what bullet holes look like, and he's convinced that nothing but a bullet or perhaps a projectile fired at high speed could have left such a hole.
His friend Cliff Joy, also a former Army man, agrees, saying such a hole could only have been made by a small round pellet travelling very fast, although he said the entry angle was strange.
The couple only moved to Taupo from Tauranga a month ago and say apart from the damage to their window, they've been very happy in their new home and have lovely neighbours.
They haven't had any trouble since the bullet incident last week and hope it was just a one-off.
"Why should anybody want to shoot us? We haven't done anything to anybody."