If you don't like folding hard tops because they add weight (about 50kg) then I don't think you'll like a hybrid (which adds up to about 300kg depending on battery size).I'm one of the 'BMW converts' that was mentioned earlier, and I've been following the development of this and the Supra hyper-closely for a couple of years now. I'm not a fan of the new Z4 (though unlike @Grasshopper , I am glad that it opted to get rid of the hard top for weight reasons, and actually really dig the shooting-brake look of previous Z3s and Z4s.). Two big reasons for this:
- No DCT. It's a good ol' ZF8. Again. Great transmission for what it is, but it's not a DCT -- and, therefore, it's limited.
- No planned ///M variant. This bodes badly for BMW's sporting intentions for the car -- and it's the main reason I don't believe it will come close to competing with the 718 as an all-around sports roadster.
That said, the Supra is rumored strongly to have a hybrid variant that will be available either at launch or soon after -- a hybrid Supra mule has been spotted/heard in multiple places. (Some of you may recall that the Lexus LC launched with a similar strategy last year.) My prediction is that BMW won't adopt that hybrid powertrain (or the coupe body style, but that's another post) for the Z4 until LCI -- likely 2021 -- and by then the car may actually compete with a next-gen 718 if it's also a hybrid -- which I personally believe it will be.
There was a recent survey in the UK where they calculated the fuel consumption of various hybrids (from company car records I believe) and found that they're no more fuel efficient than straight petrol/diesel versions - despite the very flattering mpg figures that the old official test promised. (Which made our government look pretty stupid because they've been giving big cash incentives to make people buy these cars). It'll be interesting to see how the new WLTP test rates them. Presumably they'll be downgraded very significantly on efficiency, which will make them much less attractive to manufacturers. The manufacturers already dislike them because they cut profit margins (according to Autocar) because they're so expensive to make. It may well be that they're confined to expensive sports cars in the future - but who knows.