B  with keyboard                              = 1.89 W -> daily 45   Wh
B+ with keyboard                              = 1.21 W -> daily 29   Wh  
B+ with LAN/USB chip off (no i/o except GPIO) = 0.76 W -> daily 18.2 Wh  
B+ shut down                                  = 0.26 W -> daily 6.2  Wh  
A  idle                                       = 0.7  W -> daily 17   Wh
A+ idle                                       = 0.52 W -> daily 12.5 Wh
Pi2 B at idle                                 = 1.15 W -> daily 28   Wh
Pi Zero at idle                               = 0.51 W -> daily 12.2 Wh

The powersupply for Raspberry Pi 2 and higher need atleast 2.000 mA (!) at 5V (for the RasPi 3 even 2.500 mA and more).

This is 10Watts and more.

Pi3 speed comparison with Pi2 & Pi Zero

Pi3 speed comparison with Pi2 & Pi Zero

Pi3 multi-core use – current draw

Pi3 multi-core use – current draw

Here’s where differences start to become apparent.

Hammering all four Pi3 cores takes 480 mA more than idling,

whereas the corresponding Pi2 figure was 190 mA.

And don’t forget these measurements are blind to peak instantaneous current.

Summing Up

The Pi3B uses about the same power as the Pi2B except when the A53 CPU cores are being pushed.

Then it can use ~300 mA more than Pi2B, but will get the job done nearly twice as fast.

Stressing the WiFi adds 40 mA with occasional peaks up to 100 mA. But when not in constant use, the wifi adds no noticeable difference to the overall consumption.

Source: http://raspi.tv/2016/how-much-power-does-raspberry-pi3b-use-how-fast-is-it-compared-to-pi2b