A few things in my experience aren't quite right. We have MAN 3500kg EVs, they carry the same as their diesel equivilents apart from not being LWB. The weight versus volume is very dependent on the day, the time of year, and almost every other factor you can think of. Some pet food supplier does a special on 30kg dried dog food and all of sudden the day is very heavy!!Electric delivery vans are now economical in larger towns and cities. They tend to travel at lower speeds, don't carry that much weight (mainly volume), can do dozens of stops for not many miles and EVs have an advantage in stop-start conditions. They cost more up front, but cost very little to run. Charging every night at the depot isn't an issue for them.
Up front costs are ridiculously high and even with the grant for purchase price and help with the ev charger, its still too early to say how cost effective it is. Typically the stop rate for ev vehicles is lower than fossil fuelled vehicles because it is believed that the running costs are lower. BUT with the cost of energy prices soaring through the roof this might not be the case. I have an EV tariff with Octopus which gives me 5p/Kw between 0030 and 0430, then at all other times is 25p/Kw. The depot has a flat rate of 25p and not enough chargers for the whole ev fleet, apparently there is a issue with the sites electrical design and what it can handle and presumably what the local substation can supply....I don't know the ins and outs of that but I do know that they had to install faster chargers for the MANs and that reduced the capacity for the Maxus and Nissans.
Ev vans suffer greatly with payload vs driving style and the effective range. One of our city centre drivers struggled to do his route because of his driving style. There is an argument that the way the vans are driven, loaded etc is due to the pressures of having to do your route in a certain way ie morning rush hour traffic, lack of loading bays, people parking in loading bays especially with the massive increase in uber/deliveroo/just eat drivers hogging them, deliveries having to be done before 1030, 1200 etc.
With regards to running them...my insurance is higher than having a LWB Sprinter. The Sprinter was a 316 auto which did a 52 mile round trip commute and on average 50 route miles/day, it averaged 40 mpg. The Milk Float, as I call it, does the same mileage but struggles to get 35 mpg. In fairness, with time the mpg might increase but I'm still not convinced that it is the way forward.