Being uploaded this weekend are simply some performance-per-Watt numbers comparing the A10-5800K at its stock speeds to being overclocked to 4.40GHz and then running the previous-generation AMD A8-3870K "Llano" APU. The A8-3870K was benchmarked from the same hardware and Linux software stack as its newer A10 brother.
Find the results on OpenBenchmarking.org with full system details and all of the results. Simply put, the performance-per-Watt of Trinity isn't always better than Llano. In some workloads the performance-per-Watt of Trinity is higher while in other cases it's the same or even slightly worse in select cases.
The Phoronix Test Suite is able to automatically monitor the system power consumption (via IPMI or select USB-based monitors) and also compute the performance-per-Watt for individual results by simply setting the PERFORMANCE_PER_WATT=1 environment variable or the MONITOR=all environment variable for monitoring all system sensors during testing. All of this is fully automated and seamless. In the case of this testing, a WattsUp USB power meter was used for measuring the overall AC power consumption at the power supply.
Again, see the results in full on OpenBenchmarking.org.