Power outage- don’t wanna take too much away from furnace and other household items

Well Rando, they do need some minimum amount of light not to die. A longer dark period is not a problem as long as they receive that minimum. It's a dark-dependent plant. The dark period being uninterrupted and sufficiently long enough will maintain the hormonal balance that causes "Flower" growth. It's a biological trigger within the plant. ~20dli will prevent loss of mass, i believe. Depending on how strong your lights are, you may or may not get there in 6 hours... if you are up near max over 12 hours (ambient CO2), it'll be about enough. 800-900umol/s per m^2 over 6 hours would keep them moving forward. Any amount of light in this context is a good thing... so do it for 6hours or as long as you can. if you take them outside you risk pests. If you do it, do not give them direct sunlight. They will wilt and burn. Shade needed.