Now for a good look at the power-usage numbers:
While the Intel G45 and Nvidia 9300 are showing similar results on the LGA 775 platform, the AMD power usage is showing quite a bit more variance.
Of course, the Phenom II X2 550 runs at a much higher clock speed than the Core 2 Duo E7200, so we expect a higher power draw from the AMD platforms. But what's interesting is that the 785G and 790GX boards are using so much more juice than the GeForce 8200.
Between the older 790GX and newer 785G boards, there is a power drop, which is likely because the newer 785G has a 200 MHz-lower IGP clock speed than the 790GX. In addition, AMD claims to offer better power management in the new 785G.
We do admit that the Phenom II X2 550 might be a tad overkill for a dedicated HTPC that is only going to see HD playback tasks, and we wanted to show that AMD isn't a bad alternative for power-conscious customers if fitted with a miserly CPU. The top result on the chart is from an Athlon II 250, and while it might sip a little more power than the E7200-equipped platforms, it's definitely in the same league. The Athlon II even has some respectable specs with its 3 GHz clock rate, so it's not going to fall on its face.
To put this power usage into perspective, I went over something similar in our recent 785G review, but if you missed it you might find it interesting.
I'm all for environmentally friendliness, but all too often I think the bottom-line cost for an end-user is overlooked. So let's examine the power savings of the E7200 compared to the Phenom II X2 550.
At idle, the Phenom II X2 is drawing the highest H.264 playback power draw: 110W on the 790GX motherboard. In contrast, the E7200 is drawing a low 78W on the most efficient platform, Nvidia's GeForce 9300. It looks big on the chart, but it's a difference of 32W.
In the most populated coastal cities of the United States, electricity costs are the highest in the country at about 15 cents per kilowatt/hour. With this information, we can calculate the cost to use the Phenom II X2 550 compared to the Core 2 Duo E7200.
Let's compare the worst-case scenario (a PC with a Phenom II X2 550 and a 790GX motherboard), to the best-case scenario (a machine with a Core 2 Duo E7200 paired with an Nvidia GeForce 9300 motherboard). If you turned on your HTPC and watched a two-hour Blu-ray disc every day with the Phenom II X2 550/790GX-equipped PC, and then turned your HTPC off when you were done, you would be billed $1.64 more compared to the E7200/G45 in electricity costs for the entire calendar year.
For the home user, that shouldn't be as much of a concern. I'd recommend the faster processor so that the strength is there when you need it. As for environmental concerns, Mother Earth is far better served by turning the PC off when you're not using it, as leaving it on when it isn't being used is much more wasteful.
There are two lessons to be learned here: 1) if you really care about the environment, turn your PC off (or at least configure it to enter sleep mode) when you're not using it, and 2) don't be afraid of purchasing a better processor for an HTPC based on the fear that it will cost you big money in power use.