Penthaz is a municipality in the district of Gros-de-Vaud in the canton of Vaud in Switzerland. Penthaz is first mentioned in 1011 as Penta. Pe…Penthaz is a municipality in the district of Gros-de-Vaud in the canton of Vaud in Switzerland. Penthaz is first mentioned in 1011 as Penta. Penthaz has an area, as of 2009, of 3.83 square kilometers. Of this area, 2.57 km² or 67.1% is used for agricultural purposes, while 0.52 km² or 13.6% is forested. Of the rest of the land, 0.67 km² or 17.5% is settled, 0.03 km² or 0.8% is either rivers or lakes and 0.07 km² or 1.8% is unproductive land.