dehumidifier

Peltier style dehumidifiers are very inefficient. They are cheap to buy but consume a lot of electricity for what they do. A compressor dehumidifier is more energy efficient. If you are running a ventilation fan in your tent the dehumidifier is almost useless. Most fans can exhaust air faster than a dehumidifier can dry it. So, the two fight each other. In a sealed tent a dehumidifier does not need to run much to keep humidity under control. If running a vent fan it will run almost continuously because the vent fan is constantly sucking in humid air that needs to be dried.

Wish I had your electric bill! Mine runs a little over 0/month. And when I need a dehumidifier, which is the entire length of any of my grows, it's turned on 24/7... and hang the expense because I'd rather pay a lot more on my electric bill (which the dehumidifier actually doesn't have much of an effect on) than save a little bit of money and lose my entire crop - which would make all the money I've put into my electric bill for the lights end up a big waste... not to mention my time and the money I've put into the soil and nutes and fans etc. Suck it up - turn the dehumidifier on 24/7. At 80% humidity, you are in dangerous territory. Good luck...

Photosynthesis, as a by product of creating the starches and sugars, excess water is pumped into the air by the plant. Should not be much RH at night. But even the fact you made 80rh is worrying. There is no cheap way to effectively manage that level of humidity.

40e a month. Crap, if its that cheap why not. I'm 300e every 2 months without 1. So you good going. Every 4hrs it will use roughly 1kwh..... but I'm a tent, that's sealed right, as why would you put a,dehumidifier inside a tent that sucks in undehumidified air right? If you have air been drawn into it, by way of an intake. You really should have it on the outside. Or just turn your intake so it comes on when the temperature goes up to high. Or just do what I do. Do the room. And your tent will be in a 10% dif from what your room is if you set up a negative seal. So, I do my room, and I only do 1-3 every 3hrs and yes. To avoid mold and so on. Keep it near that level. Not much you can do about it when they go into the dark. The RH just jumps right up in my environment, that's when I turn up my intakes and up the fans.. but I bother as much with RH unless it goes near 60% as its just not worth the money for the difference. Its only slight and its just taste really.