From all I've heard, these days any radar detector will only tell you that you've already been clocked.
There may still be some smaller municipalities that have the old fashioned ones, but not many. Point and shoot technology isn't just in cameras anymore.
But for your question... No, I don't use one, but I believe many detectors draw about 1/4 of an amp (300mA).
AKA: Tim & 'The Adventure Cycle' VROC #24567, NEVROC, SteelCity VROC
"When life throws you curves,
Aim for the apex."