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 1680x1050 resolution, using the same settings we did for performance testing.

In spite of the fact that the GeForce GTX 260 Reloaded is based on a much larger chip, its power use is lower than the Radeon HD 4870's, especially at idle, where Nvidia has worked wonders. The GTX 260 Reloaded-based system draws 30W less at the wall socket than our otherwise-identical system equipped with the 4870 1GB. AMD does seem to be making progress, though. The newer 1GB version of the 4870 draws less power at idle than the 512MB model.

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. 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.

Some of the quieter cards, as you can see, fell below the ~40 dB threshold of our sound level meter, which robs us of exact data but points to a happy trend toward quiet coolers. The 4870 1GB and GTX 260 Reloaded were both able to register on our meter, but just barely. Neither card is annoyingly loud, and both exhaust hot air through openings in their expansion slot covers. Oddly enough, the GTX 260 Reloaded is quite a bit quieter than the GTX 280.

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. These temperatures were recorded while running the "rthdribl" demo in a window.

The 4870 1GB keeps alive the Radeon HD 4000-series tradition of high GPU temperatures. Its only close company on the Nvidia side of the aisle is a passively cooled GeForce 9500 GT and the GTX 280.