David MacKay ouitlined the relevant physics; see https://withouthotair.com/cA/page_256.shtml and the surrounding pages (download the pdf if you prefer).
So, making the assumptions he stated in the reference, he gets 80kW generated by an ICE assuming a 25% efficiency. That translates to 20kW from a perfectly efficient engine, which is surprisingly close to your figure od 18kW
Mmm, I do love MacKay's book. Another interesting calculation I did which I was surprised worked so well was, on the basis of this power consumption at one speed, what is the top speed of the Golf GTE Mk7 (with battery depleted and engine at full bore). The engine is 148hp or about 110kW. So knowing P ∝ kV
3, I calculate k = 0.0525 for my car (power in watts). This calculates to a top speed of 128 mph. And... looking at the specifications: rated top speed 134 mph continuously.
Then back calculate this for the Golf GTI Mk7 with a 227 hp engine and presumably similar drivetrain and aerodynamic losses. That comes out around 147 mph, the vehicle has a rated top speed of 155 mph. There probably a slight deviation from a simple power law, or the 18kW figure is a low side estimate.
It's nice when maths just... works out.
Of course, that won't help when plod pulls you over for such liberal use of the accelerator. Maybe an EV is better for maintaining the licence, given they tend to top out below 100 mph. Autobahn aficionados need not apply.
EVs (including PHEVs) already outsell diesel and their combined volume is the same as hybrid (of any fuel type)...
...people do not want to buy a vehicle they feel will be obsolete in the next 10-15 years.
Combining any other type of vehicle with EV sales, including long-range PHEVs like the Volt, is grossly misleading IMO. Abolutely any use case fulfilled by an ICE vehicle, including zero access to charging, can be managed by a PHEV and there are tax credits and incentives in many cases to reduce the cost. I've nothing against PHEVs, but 100% BEV vehicles need to be analyzed in their own category if you want any meaningful analysis of consumer preferences and behavior.
As far as obsolescence, who do you think feels more obsoleted right now--the owner of a 2010 Nissan Leaf or a 2010 Honda Accord ICE?
Mmm, but both EVs and PHEVs require some form of charging infrastructure; PHEVs ideally want as much charging as they can get with their tiny battery packs, so you can consider a combined statistic as representing demand of one kind or another for charging infrastructure. Since there are no taxation advantages any more for PHEVs in the UK, these vehicles will be purchased by people who want an EV but aren't brave enough to go fully electric yet. But, yes, if you want to look at the stats independently, you can still see that battery-electric only will be, if growth rates continue as they are (and looking at other countries there's no reason to think that'll change) beating all other vehicle types by 2025. We're clearly on the exponential now.
As for obsolete Leaf - no, I don't think the Leaf is particularly obsolete. I wouldn't buy one, if only because Nissan can't build a battery pack that lasts a decent amount of time but Chademo is still a supported connector and the type 1 charging connector for AC charging is fully backwards compatible with type 2 with a simple cable. Given the really poor battery retention on pretty much all Leaf's from 24 to 40kWh (seriously Nissan, what the hell?) and the serious issues with "rapidgate" for the 40kWh models which prevent more than 2-3 rapid charging sessions in any one day, I think road tripping in any Leaf is a particularly brave adventure. But that's nothing to do with obsolescence, that's just really bad design!