It all depends on the type of grill you have, and more importantly — how quickly the charcoal needs to be completely cold. How long this takes depends on how much charcoal you have left. Be careful—adding water to hot coals can create hot steam. Make sure you water slowly to avoid creating hot steam. If you’re not in a hurry and have time on your side, consider displaying your charcoal grill the traditional, old-fashioned way.
This will extinguish the coals.
How do you cool down a charcoal grill?
If you are more experienced, try to keep the bottom vent fully open permanently and use the lid vent for temperature control. I’ve seen some people suggest simply spraying or pouring water on the coals to cool them down faster, but that’s just too risky as the sudden temperature imbalance can cause your grill chamber and any porcelain in the grill to shatter (e.g. completely prevents ingress of oxygen in the grill and burning the charcoal. By setting up a hot zone for searing and a “cooler” zone for indirect cooking, you can control how well your meat is cooked by simply moving it to the correct side of the grill rack.
Can I pour water on my charcoal grill?
Regardless of which vent you play around with, remember that open vents mean hotter and faster burning charcoal. Another danger that comes from pouring water directly onto the coals is that it produces strong steam and disperses hot ash, which in turn causes nasty burns. In these cases, use as little water as possible and then transfer all the chaos to a metal can for safe transportation. To protect yourself, your family, and your guests, find the vents on your grill before you use it, and don’t use more charcoal briquettes than you need.
Do you just let charcoal burn out?
Once the coals are completely extinguished, you can open the vents at the bottom of the kettle and hang the lid on the side of the kettle using the lid hook to let the grill cool down quickly. The charcoal will continue to burn until it is completely extinguished unless you extinguish it yourself. Knowing how charcoal works can help you do just that and make the whole cooking experience even more convenient. Just close the lid of your grill and close the vents until the ash is completely cool for at least 48 hours.
However, this technique will cause the grill to maintain its temperature for quite a while as it will take a while for the heat of the coals to cool down.