The selling point for WebP is that it can display the same quality image using less data. That means fewer bits are needed for storage and transmission, which equals faster page loads for you. Of course, Google is also interested in WebP because its bandwidth bills go down when images are smaller.
The very first public release of WebP was able to shave 45% off the file size of a PNG when it was converted to WebP, and the newest 0.4.0 release offers a 25% increase in decode speed (loading images). Besides, GIFs can now be converted to WebP for much smaller file size and smoother animation.
However, none of this applies if you’re not using Chrome. Note that, Google’s Chrome browser is the only one that natively supports WebP. If the new 0.4.0 update (currently in Chrome Beta) is able to make a dent in page load times, maybe other companies will finally get on board as browser makers do love to show off their page load times.
Source: WebP (Blog)