There are two types of humidifier out there. Evaporative or Ultrasonic
They both have good and bad. The Evaporative is a bucket of water with a fan blowing over it. Cheap and they work. I use a Honeywell HCM-710 :
The Honeywell Easy to Care Top Fill Humidifier is an excellent addition for those searching to secure a healthy and pleasant breathing environment for medium sized rooms. This humidifier by Honeywell is incredibly easy to use and utilizes a top fill design that allows for seamless filling. This...
www.honeywellstore.com
Evaporative and you can just pour tap water in the top. Very easy to fill. I did not want one with a reservoir I have to carry to the sink. It does have a "wick" inside that needs to be replaced every few weeks. I could usually get one 12 week auto grow from one wick before it was cruddy and gross. Wicks are cheap of of amazon.
Evaporative humidifiers are not as strong as an Ultrasonic.
I have an Ultrasonic that I use for my larger 4x4 tent. Another Honeywell product:
The HUL570B
With ultra quiet operation the HUL570 delivers soothing, cool visible moisture to effectively humidify medium to large size rooms making it ideal for bedroom use. It also features a wide tank opening and carry handle to make filling, emptying and cleaning convenient and easy.
www.honeywellstore.com
Again a top fill design. You can remove the reservoir on this one but you do not have to. Ultrasonics are powerful and can push the RH% beyond what the air can hold. This means it can push enough moisture to create wet drips on the walls. Ultrasonic humidifiers should be used with distilled water only. They work with tap water but it will clog up the sonic emitter. If you use tap water it can and will deposit the dissolved minerals from the water on everything in your house. A fine white dust. Use distilled water and no problems.
I looked for 2 specific things when buying a humidifier:
Top fill. No lifting a tank and trying to fill and replace. You don't want to be reaching far into the tent over delicate plants with a heavy water tank that you drop.
A mechanical on/off switch. Any of the ones with a single big plastic dial on the front are mechanical. The membrane button units are usually fancier and nicer. But, if the power goes out they are usually off until you turn them back on. The mechanical switch will be on and resume if the power cuts, which brings me to my next suggestion:
Monitoring RH. The company Inkbird make some fantastic power strips that control an outlet based on temp or RH. Perfect for plugging in a humidifier to the RH side and a heater/cooler if needed to the temp side. Check out their items. You might like them for ease of use. So.... if you plug your mechanical humidifier into the Inkbird controller - It will cycle the unit on/off until the set RH% is reached. Easy, yea?
The inkbird controllers are pretty dependable. I have been using them for about 2 years. You won't be able to check the RH from work but you can be sure that the RH is being maintained.