Alloy rims being lighter is common misconception. Alloy rims are usually heavier than steel rims. They require a lot more "meat" to even come close to the strength of steel. For example: a 16" steel rim weighs about 8 kg vs a 16" alloy rim that weighs 9+ kg, some alloys even go as high as 15 kg in this category alone, now imagine the difference between larger rims.
I agree with weight of steels at 7.6kg 16" v's 9.8kg for alloys. Also consumption went up with alloy. Put that down to aero drag from the spokes whereas steels have no spokes (or impellers). On my electric car the range was hit by 25 to 33% depending how you measure. Unchanged in town, only cruising, so must be aero.