Zwift vs Road Power

Over winter I spend a lot of time on Zwift and improved my ftp and overall power output. Now as its summer I’m spending a lot more time on the road riding and only occasionally going on Zwift. However, when I’ve been going on Zwift my power output and ftp are a lot lower than they use to be in winter when I trained on Zwift everyday training session.

However, on the road I’m hitting new pb and faster times on my rides than last year. So I was wondering if anyone could explain to me why my wattage on Zwift is lower than winter, even though I’m achieving Pbs on the road currently? I thought that my wattage and ftp on Zwift would have gone up after trialing on the road and improving my times? Thanks!

How are you measuring your power, both on the road and on Zwift?

So on Zwift, I’m using a Smart Turbo Trainer {Directo XR}
and on the road a power meter.

I experience something similar in that in Zwift my cadence is lower, while outside on a real bike I comfortably pedal at 90-100rpm and go quickly.

Zwift is with a Kickr Bike. Outside is with a Cervelo S5 with SRAM E-Tap AXS and Quarq power meter.

As long as I’m not getting slower I’m happy.