One lossless png (a screenshot) was converted to (default web quality, which is lossy) webp, and visually it was identical. Original png was 151k, webp was 23k.

One lossless png (a screenshot) was converted to (default web quality, which is lossy) webp, and visually it was identical. Original png was 151k, webp was 23k. Converting it to a jpg results in a size of 66k (equivalent quality to the webp). So in this case webp was a third of the size of a jpg. Typically, webp will be about 30-50% smaller than an equivalent jpg, which is a pretty significant amount.