Normally the answer is “zero”, obviously IMHO.
But at where I am based there is a persistent “situation” at the pumps, where people just sit after getting fuelled-up, until the last possible moment, until they are totally ready to taxi out. It creates a huge backlog on nice days and a lot of people get cheesed off. ATC do also but they can’t say anything. I am sure this situation is not unusual.
I think the main reason is that almost everybody there is being billed for the time from brakes-off to brakes-on, which creates a huge disincentive to get out of the way. It also creates a huge incentive for other dodgy practices like a fast taxi with a cold engine…
If one was being billed for airborne time (maybe that plus a standard bit for taxi e.g. 5 mins) then it would open the way for people to move off the fuel pump spot and make room for others.
IMHO one doesn’t need a taxi clearance until one wants to move off the whole pump area, and I have been doing that for years.
That’s entirely aerodrome specific.
On many airports you need permission to start your engine(s) even without moving at all, at others, permission is required to tow aeroplanes, on others again you are allowed to take off without permission…
Cant they pull the aircraft (if it is able to be pulled of course) out of the way of the pumps to somewhere just out of the way, that doesn’t need taxi clearance? I guess if you have full ATC then you need clearance even to move a couple of metres under engine power – I am assuming there is no ‘free’ zone within a few metres of the fuel pumps.
That’s what we used to do at EGLG, and even dragging the planes up to the fuel pumps across the soft wet grass in the winter. When I was renting, based on hobbs meter, that’s potentially £30 odd to pay just for moving on and off the pumps.
There might a line on the appron stating the ATC responsibility – red color. But I am not sure if it´s harmonised accross the globe.
I cannot understand why a rental place would choose to use a scheme based on hobbs. It creates an incentives to hurry up your checklists and run ups. And as Peter says it seems to create queues at the pump (although I don’t understand why they can’t just push the aircraft out of the way).
Where I’m based we pay airborne time plus 10 mins per trip. It seems fair and I can take all the time in the world while on the ground without stressing. One might argue that someone could cheat the system as the times are based on what the pilot writes down but the club ‘sanity’ checks his times with the Tach time.
Cant they pull the aircraft (if it is able to be pulled of course) out of the way of the pumps to somewhere just out of the way….
With my record on Hot Starts I find I need to do that quite a lot!
There might a line on the appron stating the ATC responsibility – red color. But I am not sure if it´s harmonised accross the globe.
Unfortunately not. Not even within one country.
I think the main reason is that almost everybody there is being billed for the time from brakes-off to brakes-on, which creates a huge disincentive to get out of the way. It also creates a huge incentive for other dodgy practices like a fast taxi with a cold engine…
If one was being billed for airborne time (maybe that plus a standard bit for taxi e.g. 5 mins) then it would open the way for people to move off the fuel pump spot and make room for others.
Slightly off-topic, but I just found out on my recent trip that the billing difference is negligible.
The place that I usually rent from charges an hourly wet rate based on the actual flight time (as noted by the pilot and obviously the airfields, in case you wanted to cross-check for cheaters… 
=). Now after lenthamen’s tip to check out the club in Paderborn, which charges based on tach time (side question: that’s not the same as hobbs, right?), I tried to budget how much EXTRA I would spend per flight leg with the engine running in the ground. I budgeted a generous 15 minutes (10 minutes prior to take-off, including run-up and some waiting time for a take-off clearance and 5 minutes after landing).
Now after the trip, I find that the sum of the actual flight time (16,6 hours) is really about the same as (actually a bit more than) the recorded tach time (16,5 hours). That’s good because I saved a lot of money by renting for half the hourly rate indeed… 
It seems natural as you’re running low RPM on the ground most of the time. The effect of course might be aircraft-specific
In the US, there is no need to call for taxi clearance to start or taxi around on the ramp until you enter a controlled taxiway. There are often cars, bicycles and pedestrians on the ramp because they don’t need clearance either. The delineation between the ramp and taxiway is typically done with a yellow hold short line, which is usually positioned where you’ve broken out from between buildings and the tower can see the plane.
Google Maps and an iPhone allow me to search around for the right photo
