I think the biggest factor is your washer. Yes, your washer!
I have a HE washer that spins the clothes at over 800 RPM's. When the clothes come out they are damp not wet. If I hang up my pillow cases under the ceiling fan they will actually be dry before the next load of clothing is finished washing.
BF has an old top loader and his clothes come out wet. So, when I am there I take all day to was 4 or 5 loads of cloths. When I am here I can wash that many before lunch.
As the clothes are only damp when they go in the dryer, they take almost no time to dry. Since the dryer only runs a little while, the costs are lower.
My old Kenmore dryer (not HE) always has the clothes dry before the next load is out of the washer, no matter if it is towels, jeans or even a comforter.
Before I bought my dryer (second hand of course) I airdryed my clothes on racks inside my apartment. There was less than $5 a month change on my bill when I got my dryer.
Of course, I wash no more than 5 loads every 2 weeks for myself.
