broadgage: 
It will happen when the electric van can be purchased on credit, and when the repayments are less than the running costs of a petrol or diesel vehicle.

As a rough guess, I would say that the cost/mile probably becomes cheaper with an EV around 20,000 miles/year. That's a lot for a private motorist, but not for a business user.

Of course it may all change when the tax benefits of running on leccy start to be adjusted.

broadgage: 
It will happen when the electric van can be purchased on credit, and when the repayments are less than the running costs of a petrol or diesel vehicle.

As a rough guess, I would say that the cost/mile probably becomes cheaper with an EV around 20,000 miles/year. That's a lot for a private motorist, but not for a business user.

Of course it may all change when the tax benefits of running on leccy start to be adjusted.