CNET lists the rating on this one as ANSI:
But Epson manufacturer page lists it as IDMS 15.4 (probably more correct than CNET, even though the general consensus is these two standards are pretty comparable).
The problem is that there are many variable affecting illuminance that aren't exactly the same as measuring brightness. Unfortunately it's more than the average consumer should need to know to make an informed purchase, and the only way to really know is put them side by side. Due to variations in projection tech (DLP vs 3LCD for instance), it's nearly impossible to develop a single standard across the whole industry.
Here's a good PCMag explainer on the topics of lumens and brightness:
And another one reviewing some tests at InfoComm
In practice, I have found the 3LCD projectors to be amazing when it comes to color and crisp even in a bright room, but I still stick in the neighborhood of 2,000+ IDMS 15.4 lumens. Considerably brighter than what the prism offers however you measure it.