If you want to run it overnight, or while you're at work, so it finishes as you arrive and doesn't leave the clean clothes in a clump for hours (or so it runs during cheaper power hours)
>and doesn't leave the clean clothes in a clump for hours
As opposed to having your clothes be in a wet clump for hours? Between the two choices I'd prefer it being dry, because I know at least there will be less microbial activity.
30p/kWh in the day, 12p/kWh at night.
Dry an entire load for less than the cost of a Day Rate kWh, simply by pressing the "delay" button a few times.