I may have missed that point. I think plug-in hybrids are optimal for those who have cheap power available. Some are sold as 'self-charging' but they should all have regenerative braking anyway. I've not seen the stats on how much hybrids save compared to the most efficient pure petrol cars. The hybrids are likely to be heavier. I suspect the manufacturers have to build them to meet various rules, but it should be about burning less oil.