From the airport to the Hilton, went to the Kenatco Kiosk and pre-paid 2500 shillings (US $25). Had to make a few trips back to the airport for work during my two weeks in Nairobi and from the Hilton Kenatco was 1900 shillings (US $19) each time. Also during my stay, needed a car for a day a few times, and other times just needed a one way fare. The Hilton hooked me up with Kenatco each time. Overall was very happy with them, good service, nice cars.
But one story for you - on my last day I was in a Kenatco taxi on the way to the airport at night and at a police checkpoint we were waved over. After the cop looked at the car he said something to the driver and waved us on. What was that all about? The driver said that the cop apologized for having pulled us over. In the dark he had not seen the Kenatco markings on the side of the car So? Why would that matter?
The driver explained that Kenatco was owned by the Kenyan govt and had been established to provide "first world comfort" to visitors from abroad. And that includes not being shaken down for bribes by the beat cops or anyone with a badge. I asked if that was a problem and he said "yes", the cops see a white person in a taxi and the next thing you know there is an "inspection" and then something is "out of order" and then there is a "fine" to be paid...
He said they cant mess with Kenatco taxis - if a cop tried that with his car he is supposed to use his radio to call dispatch immediately and that cop would be in big trouble. And the cops know that, hence they dont even try with Kenatco taxis.
Mind you, this was not some driver telling me this on my way into Nairobi from the airport on Day 1 to scare me into using his business while I was in town. This came up after two weeks of using them and only because I asked.