The tank your grill takes
Almost every gas barbecue sold in the United States runs on the same 20lb cylinder: the squat steel tank that sits in the cabinet under the grill, with the grey plastic collar and the QCC-1 valve. That is the one we deliver. If you bought your grill at a big-box store and it has a tank underneath it, this is the tank.
A full one holds about 4.7 gallons of propane and weighs roughly 37lb, against about 17lb empty. That weight is exactly why this service exists. Carrying one up a Brooklyn stoop is manageable. Carrying one there from a refill station on the far side of a bridge, without a car, is not.
How long a tank lasts on a grill
A typical gas grill burns through a 20lb tank in somewhere around 18 to 20 hours of cooking on high. In practice, for a household that grills most weekends through the summer, that is a large part of the season on a single tank.
Cook on medium and it stretches further. Run a big six-burner or a side burner and it goes faster. The honest answer is that you will not track it, which is why the people who never run out are the ones who keep a spare cylinder and swap the empty as soon as it happens, rather than the night they need it.
Running out mid-cook
The classic failure is the burner fading halfway through a tray of chicken. There is no fixing that quickly: no propane means no grill. If you would rather it never happened, order two tanks. The second one costs the same delivered price and it sits in the yard as insurance.
If it has already happened, call or text. Say what borough you are in and how fast you need it, and Rodrigo will tell you honestly whether he can reach you today.