There's a "Dry" button on the bathroom control panel. Is it only for drying the bathroom itself? Half right. On a typical Japanese bathroom ventilation dryer (a ceiling unit that vents, heats and dries), dry mode is also used to dry laundry hung inside the bathroom.
So this works: wash, hang the clothes in the bathroom, switch on Dry, and the clothes and the bathroom dry together. No more hanging things outside, and fewer tense negotiations with the weather forecast. But it doesn't mean "no hanging at all," it means "no hanging outside." Hang clothes on a laundry rod or similar, and leave gaps so air can move through.
Here's how the modes split up: Dry dries clothes and the bathroom, Ventilation pushes humid air out, Heating warms the bathroom, and Cool Air blows air on models that have it.
So the lazy-person setup is laundry day = Dry, non-laundry day = Ventilation. On laundry day, hang well-spun clothes and run Dry. On days you don't wash, just ventilate after your bath. You're not adding a new chore. You're piggybacking bathroom humidity control on laundry you were doing anyway.
Door open or closed?
During Dry, keep the bathroom window closed. If the door has an air intake vent, close the door and leave the vent open. If there's no vent, some makers tell you to leave the door slightly open, so check your manual first. The 24-hour ventilation is a function that keeps the whole home gently ventilated at low airflow, so the key is not to block the air supply path.
Getting the bathroom back to a dry state quickly helps against humidity and mold, but "Dry button = mold gone forever" is not true. You still need to clean as usual.
How much per run? Is 1.5 hours realistic?
This varies a lot by model. In one example, the MAX BS-161H-2, strong drying uses 1,190W. At 31 yen/kWh, that's listed as about 37 yen per hour. Run that example for 1 hour 30 minutes and it comes to about 56 yen per run (37 yen x 1.5 hours).
At 3 times a week, that's roughly 13 runs a month, or about 730 yen. At 4 times a week, roughly 17 runs, or about 950 yen. Actual cost depends on your rate plan, your model, the mode and the drying time, so it's not "bathroom drying always costs 56 yen." It's an estimate for a 1.19 kW electric unit running 1.5 hours.
In the same MAX example, 24-hour ventilation draws 6W, which at 31 yen/kWh works out to about 134 yen per month. So Dry only on laundry days, 24-hour ventilation the rest of the time is an easy way to split the roles between features and running costs.
Drying time depends on the model, the season, room temperature and humidity, load size, fabric and how well the clothes were spun. Some makers set the default to 3 hours, so adjust based on how dry your clothes actually get and whether 1.5 hours is enough.
It also helps to put the lid on the bathtub, cut down on dripping water, avoid cramming clothes together, and hang thick items where the air hits them. Packing T-shirts shoulder to shoulder and then complaining "they're not drying!" is like yelling "drive faster!" at a traffic jam on the expressway.
Bottom line: a bathroom dryer isn't something that adds chores. It's equipment that bundles two jobs together: drying your clothes and not leaving the bathroom damp. For a load that dries in 1.5 hours, the electric example above costs about 56 yen a run. That's not a trip to the coin laundry every time, and it can fit straight into your laundry routine.
