Although new LGA1155 Celeron processors have declared 65 W TDP, like other dual-core processors designed for the same platform, it doesn’t mean anything in reality. In the real world they should be more energy-efficient, because they work at low clock speeds and have a small L3 cache. To check whether this assumption is correct, we performed additional testing.
The graphs below show the full power draw of the computer (without the monitor) measured after the power supply. It is the total of the power consumption of all the system components. The PSU's efficiency is not taken into account. The CPUs are loaded by running the 64-bit LinX 0.6.4 utility. We enabled all the power-saving technologies for correct measurement of the computer's power draw in idle mode: C1E, AMD Cool'n'Quiet and Enhanced Intel SpeedStep.
Things are quite what we expected them to be in idle mode. Celeron G540 based system needs a little less power than a similar system based on a Pentium processor. However, Socket AM3 or LGA775 platforms with older and simpler CPUs of the same class inside consume about 2-3 watts less.
I would like to say a few words about Celeron G440. This CPU consumes in idle mode so much power because it doesn’t support EIST and doesn’t drop its Vcore in this case.
Under peak load the situation changes just a little. Celeron G540 can’t retain the title of the most energy-efficient CPU in our today’s test session. The system with the older Celeron E3500 consumes much less power. Although in terms of dedicated performance per watt, faster Sandy Bridge will be beyond competition.