A fresh install of GrapheneOS has far lower idle power usage than the stock Pixel OS. Power usage while active is comparable. Making a similar setup to the stock Pixel OS by installing sandboxed Google Play and a couple dozen apps doing a bit of background work will result in similar battery life.
@GrapheneOS This thread sounds an a lot like "GrapheneOS battery life is very much the same as stock Pixel OS". Could you explain what I am missing here?

@gbsills If people use sandboxed Google Play with a lightweight setup and don't have other stuff heavily running in the background, they'll tend to get better battery life. The stock Pixel OS has a ton of stuff installed and running in the background by default.

Many people don't use sandboxed Google Play or keep it in a dedicated profile they don't usually have running. They can get much better battery life if they avoid apps doing inefficient background work and use UnifiedPush for push.