Thanks for these posts, very interesting for me. Murphy's law that I should read them less than a day after putting down a deposit on a new ICE bike!
Whilst £1,500 will be a welcome subsidy for a new bike, unfortunately it just isn't enough IMHO.
The NC750S DCT I'm picking up next week has a list price of £6,500. It is the most comparable ICE bike to a 2015 Zero S I can find. Similar performance, ABS, no gear changing and relatively low maintenance. I doubt there'll be much change from £13,000 for the Zero, so the Honda is exactly half the price. Even with the subsidy (which isn't available yet so no guarantees), I would have to chew through £5,000 of petrol and additional servicing on the Honda for the Zero to start making financial sense.
At current petrol prices, my 12,000 miles a year of commuting and (not enough) riding for pleasure will cost £850 in petrol on the Honda. Shall we say another £400 for the extra servicing a year? It makes the maths simple: £1,250 a year in extra running costs for the Honda over the Zero. I'll be generous and forget about the cost of electricity to run the Zero, which should soak up any other minor costs of the Honda over the Zero - like road tax.
So I'd have to own and run a Zero S for 4 years before breaking even with the Honda. I'd also need to keep my Fazer for my occasional longer rides.
The final nail in the coffin is that I'll have paid off the Honda in three years time, at which point I'll most certainly be ready for a new bike. I would have to finance the Zero over five years, which is a very long time to be paying off a bike apart from anything else. If I do keep the Honda for five years, I'll have had a couple of years to start saving for a new bike. At which point I hope there will be a 2020 Zero SR available and that I'll be able to afford it!