Thanks for the various bits of info. Its quite good to get back to digging out and reading life cycle reports although my day job was for the built environment rather than vehicles.
There is an interesting report on life cycle of EVs versus ICE from the Union of Concerned Scientists in the USA dated 2015. Generally, even with the relatively dirty USA electricity at that time, EVs were better than ICE vehicles on a life cycle basis. With cleaner grid electricity the advantage is getting better.
The full report is linked below and the Exec Summary is at
https://www.ucsusa.org/sites/defaul...er-Cars-from-Cradle-to-Grave-exec-summary.pdf
I've also found the average embodied CO2 per kWh for grid electricity in the USA was 0.439kgCO2/kWh in 2017
Assessing the evolution of power sector carbon intensity in the United States - IOPscience and the equivalent figure in 2018 for the UK was 0.281 kgCO2/kWh
Greenhouse gas reporting: conversion factors 2018
The average for diesel is 2.65 kgCO2/litre on same basis from same UK report. So for my allegedly inefficient I-Pace at say 40kWh/100 miles thats about 11kg CO2 and a good diesel at say 60mpg thats about 20kg CO2. Lets ignore the other diesel emissions.
Of course if you have a fully green electricity tariff you could argue that you have near enough zero CO2 emissions depending on how you account for embodied CO2 in the transmission system and the actual power generation equipment.