Just put it into the case, and place in aircond room. The aircond only on during night when u sleep and sometimes in the day...no need 24/7.
The proper case will restrict the fluctuations of humidity.

As for the dehumifier beads...tried that route before..even bought a whole large metal can of it...and even the giant store humidifiers where it collects water...place inside the case.. use to do that only when u do not have air cond.

Been storing my taylor 310 that way for more than 10 years in aircond room chuck under the bed, and a Norman solid top as well.

Can't quantify the electricity bill, as i only on the aircond during night time mainly and daytime only when in room.
But i do not turn on the aircond specifically just for the guitars, the guitars basically tumpang the aircond only when its switch on for daily use.

But i do believe that quality cases like the Taylor stock hardcase makes a difference in regulating extreme fluctuating in humidity...compared to a bare guitar in a aircond room that switch off-on periodically..

The other DIY method i previously practiced was, i put a few humidifier bead packets into a mini ziplock bags, and punch holes on it. Then i attached a string to that bag, and loop it to the bridge pins. Then the ziplock bag goes into the guitar thru the soundhole, and store the guitar in the case.

When i wanna play, i just pull out the ziplock bag. And change periodically when it turns color.

I was able to buy like 10kgs of these humidifier packets many years ago by chnace from a supplier, but now i got no idea where to source this stuff.