BUY WITH YOUR HOME IN MIND
Choose for size and warm mist
Choose the HM311S if you want smart cool-mist humidification in a smaller, lighter machine. Choose the HM713S if the extra water reserve and warm-mist option would be useful enough to justify a taller body and more weight.
Both models already have a humidity target, controls on the unit and Dreo app support. Moving to the HM713S is mainly a change in tank size and mist options. You do not need the larger model just to get automatic humidity control.
The smaller model is easier to lift
The HM311S is shorter and lighter when empty. That matters if you often carry the tank to a sink, lift the machine off a table or move it aside for cleaning. It also leaves more space above the lid on a suitable open surface.
The HM713S holds more water. At the same rate of water use, that gives you more reserve between refills. It also gives you more water to lift when the tank is full. A smaller jug may be easier to manage than carrying the filled tank.
Tank capacity alone does not establish how long either model will run in your room. A higher output setting uses water faster, while automatic control can reduce or pause mist once the sensor reaches its target. Choose by the refill routine you can comfortably keep up with.
Both offer the smart features that matter most
Each model lets you set a humidity target instead of relying only on a fixed mist level. You can make everyday adjustments on the machine, with the app available for remote control and other settings.
The HM311S is therefore worth keeping on the shortlist even if you want a smart setup. The HM713S adds a visible humidity indicator and warm-mist choice, rather than turning a basic manual machine into a smart one.
On either model, the sensor reads air near the unit. Leave it clear, aim the mist into open air and check a separate humidity meter elsewhere in the room if the display seems misleading. Raising the target is a poor fix for mist that is landing back on the sensor or nearby furniture.
Decide whether you will actually use warm mist
The HM311S provides cool mist. The HM713S can heat water for warm-mist operation and can also run in cool mode. If you expect to use cool mist all the time, the smaller model may already cover the features you need.
Warm mode adds a heating step and a cooldown routine before handling wet parts. Keep the unit where children and pets cannot reach it, and follow the manual before refilling or cleaning after heated operation. A warm setting does not make the tank self-cleaning.
Do not choose the HM713S on the assumption that heated mist will fix every dry room. A portable humidifier still needs suitable placement, enough output for the conditions and sensible humidity settings. More water in the tank is useful reserve; it is not a guarantee of even humidity across several rooms.
Water and cleaning remain shared jobs
Both are ultrasonic humidifiers. Distilled or suitable purified water helps limit mineral residue, and both still need old water emptied and wet parts cleaned. Their optional mineral cartridges do not make every type of tap water equivalent to distilled water.
Top filling makes adding water convenient on both models. Check that you can remove the lid, reach the opening and lift out the tank without hitting a shelf. Keep water out of the air outlet and electronics, and do not keep topping up old water just because the lid is easy to reach.
Reviews praise convenience and quiet use on both listings, but neither has a clear reliability advantage in the feedback available. The HM311S draws cracked-tank and durability concerns; the HM713S draws leakage and early-failure concerns. Those are useful cautions when considering the return policy and care routine, rather than proof that one will last longer.
Which would fit your routine?
The HM311S is the simpler choice when you want cool mist, automatic control and less to lift. The HM713S makes more sense when you have a suitable spot for the larger body and will make use of warm mist or the larger water reserve.
If the recurring job of buying low-mineral water is the main problem, consider an evaporative design instead. Changing the way the machine adds moisture may help more than moving between these two ultrasonic models.
If the heating option is the deciding feature, read warm vs cool mist humidifiers for the differences in handling, electricity and water care.
If you would rather use a wick than manage mineral mist, our ultrasonic vs evaporative guide explains the change in design.
Before choosing the larger body, check where to put a humidifier so there is room for airflow, filling and safe handling.