Crested geckos come from humid island forests where temperatures sit close to a comfortable room, and that origin flips the usual power-cut advice on its head. Most crested geckos face more danger from an owner sealing the enclosure beside a heater or piling in heat packs than from a night without equipment, so the calm priorities are a stable interior room, humidity kept up with stored water, and temperature checks before any attempt at warming.
Room temperature is the starting point, not the problem
Move the enclosure, if it lifts safely and stays upright, into the warmest interior room away from external walls, windows and draughts, or insulate its current spot lightly with a blanket over the back and sides while leaving the top ventilation open. Resist hot-water bottles inside the enclosure, heat mats pressed to the glass and placing the tank near a fireplace or fuel heater, all of which can push a small glass box into stressful heat quickly and unevenly, and fumes from combustion heaters are a hazard in their own right. If the house genuinely cools hard over many hours, a wrapped bottle of warm water stood outside the glass, checked often and removed as it fades, gives a gentle nudge without creating a hot spot the gecko cannot escape inside its own home.
Humidity and food while equipment is off
Mist the enclosure with stored, treated water at room temperature in the evening as usual, since the mister or fogger is off but the gecko still drinks droplets from leaves and needs the humidity rise for a clean shed. Prepared crested gecko food can be offered as normal if temperatures are near usual, because digestion in this species is not tied to a basking lamp, but replace it on the normal schedule rather than leaving it to spoil in a warm room, and refresh drinking water if the dish is fouled. Avoid handling beyond necessity, since a startled leap can cost a gecko its tail, and outages are exactly when startles happen.
Doors, lids and a gecko built to climb
A crested gecko explores upward, sticks to glass and squeezes through a door left resting on its latch, so check the enclosure is genuinely closed after every misting and temperature check, and count on torchlight hiding a gecko pressed flat behind a plant rather than proving it missing. If you must move the gecko itself, coax it onto a hand and into a ventilated, securely lidded tub with a damp paper towel and a piece of cork, kept in the same warm room, rather than carrying it loose through a dark house. When power returns, restart misting equipment and check its timers rather than running a long catch-up fog that saturates the enclosure and cools it by evaporation.
Watching recovery and preparing for next time
In the days after a cold outage, look for a gecko that stays hidden through its normal active hours, refuses its prepared food repeatedly, keeps shed stuck on toes and tail tip despite restored humidity, or shows a wavy, soft-feeling tail that can signal longer-term problems worth a vet's opinion. Contact a reptile vet if appetite does not return with normal conditions, shed will not clear, or the gecko becomes weak and unresponsive, and mention the lowest temperature you recorded. Then assemble the small kit this species actually needs: stored treated water, a hand mister, spare thermometer batteries, a latching tub and this plan written down. Should this gecko slip beyond the house while the power is off, the KinsLe Lost Pet Alert System gives whoever picks it up a straight route back to you, which suits a pet small enough to hide in a houseplant for days.