Bluetooth range and Power
Each particular Bluetooth module will have a maximum amount of transmit power, like +8 dBm, and you can run up to that maximum (using more supplied power to the module) or run at a lower level.  The higher the transmit power, the longer the range.

But you also have to be able to receive the signal from the other end.  Each module will also have a corresponding receive sensitivity, the lower the better  (i.e. -98 dBm is betetr than -86 dBm)  This number is fixed for each module and not something you adjust.  A high transmit power with a lousy receiver sensitivity doesn't help.

Different chips will be designed to run at different levels of maximum power, and type of transmitter.

Using some of the Bluegiga modules, whith which I am the most familiar, some figures are:

Model       Max Transmit      Max Receive Sen      Range (m)

WT12         +3 dBm            -86 dBm              20-30
WT11i       +17 dBm            -86 dBm              100-300
BLE112       +3 dBm            -93 dBm              30-150
BLE121LR     +8 dBm            -98 dBm              450


The WT12 is a class 2 "classic" Bluetooth module, and the WT11i is a class 1 "classic" Bluetooth module.  The last two are both BLE (Bluetooth Low Energy), aka Bluetooth 4.0.  Note that the BLE121LR (LR for long range) gets a much greater range using +8 dBm of transmit power than the WT11i does with 17 dBm.

The range figures in meters are all for line of sight, outdoors.  Figures for indoors, or outdoors with obstructions, will be lower.

In the past, it was pretty much the case Bluetooth range was limited to 100 meters.  You can see with different modules, you can now go anywhere from 20 to 450m.

Note: these figures were all obtained with the built-in "chip" antennas on the Bluetooth modules.

I have no association with Bluegiga other than being a customer.