Anglian Water will take delivery of around 500 Vauxhalls in 2012 after having a similar number join its fleet in 2011.
The water company has relied on Vauxhall vehicles for over a decade, with around 90% of its 2,000-strong fleet coming from the manufacturer.
"Put simply, our current fleet is the best, most cost-effective solution we've ever had," said Nigel Allen, Anglian Water's fleet manager.
"Vauxhall has worked closely with us to help us get to where we are today and there's always someone on the end of the phone. We've been constantly impressed with the vehicles' prices, maintenance costs and residual values.
"The two major drivers for our fleet decisions are whole life costs and CO2 emissions, both from an environmental and financial point-of-view. The whole life costs of all our Vauxhall vehicles - both cars and vans - are incredibly impressive and we also see the benefit of the ecoFLEX models in our fleet, including the New Combo and Vivaro ecoFLEX."
Anglian Water's fleet of 2,000 vehicles includes 1,200 light commercial vehicles, 600 cars and 200 trucks and heavy vans. Around 90% of the car fleet is comprised of Vauxhalls including Corsa, Astra and Insignia, and Vauxhall commercial vehicles make up more than 95% of the van fleet, including New Combo, Vivaro and Movano models.
Allen continued: "Our fleet vehicles are owned by us for four or five years. We sell the cars on once they clock up 100,000 miles and the vans when they reach 120,000 miles. Given the mileage involved, it's important our fleet is not only efficient and cost-effective to run, but absolutely dependable."
When any new parts are required, Anglian Water benefits from next-day delivery through Vauxhall Trade Club, helping to reduce downtime.