How much does your humidity/VPD fluctuates?

You probably need a dehumidifier even if you run lights at night. The biggest factor when lights go out is the drop of temperature and potential condensation. i run a space heater during my dark cycle. I set it based on temperature and RH when lights are on and reference the resulting dewpoint. Around 27-30C and 50% give or take, you end up with a dewpoint that's in middle to upper 60s F. (sorry for mixing of imperial/metric.. my themometer in tent is C, but my space heater is F, so this is what i am familiar with off the top of my head) In vege phase, my room only gets to 24C but in flower i am 27-30C with lights at 100%. I set my space heater much lower during vege to save watts. Do not let it hit the dewpoint, even if only for a short period when lights go out, temps drop, and a dehum can't quite keep up with rising RH. Get a space heater and set it 1-2 degrees above dewpoint. may need some trial and error if you want to save as many watts as possible. i shoot for +2F from highest dewpoint i'll see. If you have a dehum, could just have the space heater on for first couple hours of darkness and make sure the dehum has enough time to lower RH properly. at that point, dewpoint is reduced to some value you'll likely never hit. so, lights go out, temps start to drop, but dehum has enough time to wrangle RH%. then, space heater can turn off and temp can drop further with no condensation occurring. many space heaters have a 2-4-8 hour timer setting then shut off. So, when my temps are high during lights on, i reference where the dewpoint is, and i keep it a couple degrees above that point. i am absent-minded, so resetting my space heater every single night isnt something i want to do, lol. i'll spend a few extra dollars to avoid it, because i will forget and i will get condensation and it;s a fucking disease vector from hell. many combinations of temps and rh equate to the same VPD. temperature still has it's own effect. 25-30c is a good target and then whatever RH% results in proper VPD is what you should try to maintain. warmer is better than colder -- given common sense. i.e. don't run at 35C no matter what the VPD is, lol. 1.3-1.5 vpd isn't going to ruin vege growth. Is it better at 1.1-1.2ish? probably. Is such a small variance a huge difference? probably not. Avoiding dewpoint and massive catastrophe that is white powdery mildew more than makes up for it.