In regards to maintenance costs, if a plugin hybrid is driven on electric 95% of the time (i.e, if it has a 60 - 100 mile electric-only range) then the gas engi

In regards to maintenance costs, if a plugin hybrid is driven on electric 95% of the time (i.e, if it has a 60 - 100 mile electric-only range) then the gas engine won't need maintenance that much (assuming things like oil changes and spark plugs are based on engine-running mileage). As far as overall complexity, a regular hybrid with a modern ECVT transmission (like Ford and Toyota have) is actually a lot simpler than a traditional automatic transmission. Then the plugin version is the same thing but with a bigger battery. For weight, a plugin-only with 350 mile range would have as much weight as a plugin-hybrid with a 60-100 mile electric range and a low horse power gas engine (the gas would be used to maintain highway speed and trickle charging the battery, and electric used for acceleration).