It's hard to quantify, but when I switched from the Nexens to Michelin CrossClimate+'s, I would say my 4.2/4.3 mi/kWh average dropped to 3.8/3.9. But it has also been getting a lot colder, so it's hard to say for sure if it dropped a LOT.
I think I remember you were in FL, right? You won't need a super grippy tire like the Crossclimate for winter use, so perhaps there are other LRR tires out there that would work well?
Incidentally, I've been having issues with the CrossClimate+ tires, and am going back this afternoon to have them try to rebalance them, or perhaps change them out to something else. Leaning towards the Nokian WRG4 as that was my second choice (and some others on this forum reported having those tires as well on the Kona).