Our test system is based on a power hungry Core i7 965 / X58 based. This setup is overclocked to 3.75 GHz. Next to that we have energy saving functions disabled for this motherboard and processor (to ensure consistent benchmark results). On average we are using roughly 50 to 100 Watts more than a standard PC due to higher CPU clock settings, water-cooling, additional cold cathode lights etc.
Keep that in mind. Our normal system power consumption is higher than your average system. We'll take one reference card as example:
Graphics card
1. Advertised GeForce GTX 460 TDP = 150W (768MB) 160W (1024MB)
2. System in IDLE = 178W
3. System Wattage with GPU in FULL Stress = 307W
4. Difference (GPU load) = 129 W
5. Add average IDLE wattage ~ 25W
6. Subjective obtained GPU power consumption = ~ 154 Watts