Deary me.. What a question! One that has been covered by others here pretty well. I went solo (power) after I had done around 30 hours.. Up to that point I had done many landings at other airfields (including grass) I was able to demonstrate that I could select a field for an outlanding (my glider time came in handy for that). Added to that I went through a heck of a lot of different techniques like side slipping on approach, dealing with low level thermals on finals (i could have killed the local corn field for that).. The list goes on.
I'm sure that my instructor could have sent me off at least ten hours before he did. But when he did let me go. I certainly felt happy and able to deal with virtually everything that could be thrown at me..
On my solo they changed runways on me. Obviously I could have said (and my instructor made sure that it was my call as to anything they asked me to do) that I would prefer to use the runway that I took off from. I was happy to do as they say and it wasn't a problem. What I wasn't ready for, was the fact that the aircraft floated on and on (AA5) and I lost my nerve and opened her up to go around to try again.. Little hairy as I didn't anticipate the nose going up when I opened the throttle
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It was another four hours before I went solo again.. I made sure that I got some practice in at going around at low level.. Different ball game to touch and go ...
Sorry to have gone on a bit.. But it may help others to decide when they may be ready.. Don't be in a rush. Try and get your instructor to cover some of the more unusual things, so that they don't bite you when you least expect it... Ohh!! And if you have any doubts or holes that you want filled before you go it alone.. For Gods sake speak to your instructor!! There is no shame in taking a bit longer before going solo. It's far better to be safe than end up a statistic somewhere.
Astral