Distilled water is somewhat expensive, and humidifiers chew through water in the winter (at least here). I quickly switched away from ultrasonic for that reason, 6-8 litres of distilled water per day for a medium sized apartment is not sustainable. Evaporative with tap water and biocides is the way to go.

The air outside is extremely dry (<5% relative humidity once heated to indoor temperatures), and the air is quickly replaced by the ventilation. I have anecdotely heard that in the US they have much lower requirements of rate of air replacement than here in Sweden though, so maybe that could work there, but then you would also have stale air, which doesn't sound great.

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peteyPete an hour ago | parent [-]

A reverse osmosis filter will provide plenty of water with nearly no minerals. They're available to install under the sink/counter for a few hundred bucks and provide clean drinking/cooking water and work fine with ultrasonic humidifiers without the issue of depositing minerals everywhere / clogging up the ultrasonic emitter. So its a lot cheaper than buying it plus you get great water.

	▲	VorpalWay 41 minutes ago \| parent [-]
		Those aren't exactly common here, since municipal water is high quality and everyone drinks it as is. It is not like some parts of the world where the tap water is full of chlorine and barely drinkable (I ran into that when I went to Athens). And if you have your own well, you generally do a cheaper filter targeted at whatever impurity you have (such as an iron filter), rather than a reverse osmosis filter. With reverse osmosis the water also gets too pure for drinking and you need to add back minerals to it for safety, it is not healthy to drink ultra pure water for any prolonged period of time.