MacTracker provides detailed information for every mac ever made
If your mac has bluetooth 4.0, it supports Bluetooth Low Energy.
Here is a screenshot from Mactracker
For reference, Bluetooth 4.0 became standard on Mac Computers in mid 2011
system_profiler also returns a plethora of information about the hardware. Run the following from the command line.
system_profiler | grep -m1 -i 'Bluetooth -- LE'
A Mac with BtLE will return the following
2014-01-15 22:26:46 -0700 kernel: Bluetooth -- LE is supported - Disable LE meta event
A Mac without BtLE will return nothing.
My answer is correct for using a GUI to find this information, MrWonderful's answer is better if you want to do this from the command line.