I mean, yeah. Anything taking juice will put it into hybrid mode sooner.
That said, i very much don’t think that it’s 4-5kw. In winter with the heating going, the range drops by around 7 miles (from 39 to 32 on full charge), a preheat for 5 minutes takes around 3-5 miles. Maybe if you heat to 25 degrees, but not to 22-23 where we set it at.
I actually am pretty certain about this since you can preheat the Golf on the granny charger (it’s not bypassing the battery, it’s topping it up as fast as you use it) – but only up to 22 degrees. A VW granny charger delivers 2.2kw, so it has to be somewhere around that number.
If the journey is anything more than local i preheat while the car is plugged in anyway, so it does have zero impact. If i need to extend by a little (one hospital is 36 miles round trip) and feel particularly tight, we stop the heating half way on the return trip and only use the seats and wheel to heat (or sustain, rather) the interior. That’s pretty rare though. Generally, i just spend the 50p in petrol to get home, or drive in hybrid on the most strenuous part of the journey (uphills, 70 zones etc).
I will say, i don’t think that in your example, with the engine running every now and then to sustain heat, rather than just driving the last 3-4 miles on the engine itself makes a big difference in consumption. Particularly if we take into account that, if the engine in your car is running for the heating at a red traffic light, it will also use it to accelerate “while it’s at it”.
But, yeah. Our electric journeys are 100% electric in winter. No petrol engine required. Which also has the advantage (and we noticed that very quickly) that the car basically instantly blows warm air, from cold.
Here’s some info on how this all works, including a diagram for the high/low temp circuits, the part about auxiliary heating etc. That’s for the MQB platform, doesn’t apply to the Tucson (but both our GTE and Tiguan). A few things have been facelifted (battery size, engine size for the Tiguan etc), but the concept still applies.
https://www.greencarcongress.com/2014/04/20140403-mqbphev.html
Prior: SEAT Ateca Xcellence Lux 1.5 TSI DSG MY19, VW Golf GTE PHEV DSG MY23
Current: Hyundai Ioniq 6 Ultimate
Next: we'll see what's available in 2028.