Power consumption
We measured total system power consumption at the wall socket using an Extech power analyzer model 380803. The monitor was plugged into a separate outlet, so its power draw was not part of our measurement. The cards were plugged into a motherboard on an open test bench.

The idle measurements were taken at the Windows Vista desktop with the Aero theme enabled. The cards were tested under load running Half-Life 2 Episode Two at 2560x1600 resolution, using the same settings we did for performance testing.

Well, not bad. The GeForce GTX cards pull less power at idle than the 9800 GTX or the Radeon HD 3870 X2. They're not quite down to Radeon HD 3870 levels, but this is a much larger chip. When running Episode Two, the GT200 cards' power draw shoots up by quite a bit, but remains well within reasonable limits.

Noise levels
We measured noise levels on our test systems, sitting on an open test bench, using an Extech model 407727 digital sound level meter. The meter was mounted on a tripod approximately 12" from the test system at a height even with the top of the video card. We used the OSHA-standard weighting and speed for these measurements.

You can think of these noise level measurements much like our system power consumption tests, because the entire systems' noise levels were measured, including the stock Intel cooler we used to cool the CPU. Of course, noise levels will vary greatly in the real world along with the acoustic properties of the PC enclosure used, whether the enclosure provides adequate cooling to avoid a card's highest fan speeds, placement of the enclosure in the room, and a whole range of other variables. These results should give a reasonably good picture of comparative fan noise, though.

I wasn't able to reliably measure noise levels for most of these systems at idle. Our test systems keep getting quieter with the addition of new power supply units and new motherboards with passive cooling and the like, as do the video cards themselves. Our test rigs at idle are too close to the sensitivity floor for our sound level meter, so I only measured noise levels under load. Even then, I wasn't able to get a good measurement for the GeForce 8800 GTX; its cooler is just too quiet.

All of Nvidia's new-look coolers are louder than the incredibly quiet dual-slot cooler on the 8800 GTX. The GTX 260 and 280 both put out a fairly noticeable hissing noise when they're running games, as our readings suggest. I wouldn't consider them unacceptable, because they're nice and quite at idle. And, as you'll see, I think there's a reason the new GPU coolers are louder.

GPU temperatures
Per your requests, I've added GPU temperature readings to our results. I captured these using AMD's Catalyst Control Center and Nvidia's nTune Monitor, so we're basically relying on the cards to report their temperatures properly. In the case of multi-GPU configs, I only got one number out of CCC. I used the highest of the numbers from the Nvidia monitoring app. These temperatures were recorded while running the "rthdribl" demo in a window. Windowed apps only seem to use one GPU, so it's possible the dual-GPU cards could get hotter with both GPUs in action. Hard to get a temperature reading if you can't see the monitoring app, though.

Looks to me like the 8800 GTX is so much quieter than newer cards because it's willing to let GPU temperatures climb much higher. 84°C is pretty warm, so I can't complain too much about the acoustics of the later cards.