No tank can be promised to last every night without knowing output and room conditions. Compare Levoit LV600HH with Classic 300S, then estimate water use at the setting you need. LV600HH is the documented hybrid model; “LV600CH” should not be used as an interchangeable model code.

A useful overnight calculation

Measure how much water is consumed during a typical session, then divide by its duration to estimate hourly use. Multiply that by your intended night length. Repeat on a colder or drier night before relying on the estimate.

This is an observation method, not a laboratory runtime claim. Automatic control may cycle, while maximum output can empty a tank sooner. A headline “up to” figure normally describes particular conditions and should not be treated as your minimum.

Which controls do you need?

LV600HH offers warm and cool modes and humidity control. Classic 300S is a cool-mist smart option. Compare the filling and cleaning arrangement, display behaviour and required space rather than only the nominal tank size.

If warm mist is not needed, do not choose it solely because a larger electrical rating sounds more powerful. Account for hot-water and steam risks wherever the unit will stand.

Do not trade cleaning for reservoir size

A tank large enough to retain water for several nights still needs its prescribed care. Do not top it up indefinitely without the emptying and cleaning routine. A full reservoir also adds handling weight if it must be carried.

Check room humidity before bed and in the morning. If condensation develops, reduce or stop output and reassess the conditions instead of buying an even larger tank.

Check the model before checkout

The Amazon links are searches. Match the complete model, supplied parts and intended use; search results may include other variants or replacement accessories. We have not measured these units side by side or confirmed seller stock. A published maximum runtime is not a promise for your room or setting.

Follow the exact manual for placement, water, cleaning and any permitted additives. Filter-free does not mean cleaning-free. A humidity reading and inspection for damp surfaces are more useful than running a unit continuously because its tank is still full.

Sources and method

This comparison checks the published product identity and intended use. It is not a hands-on test or a guarantee of seller stock, price or performance in your home.