It typically consumes less than 500MB–800MB of RAM upon a fresh boot, compared to the 1.5GB+ used by standard Windows 7.
While the performance gains are impressive, using a custom ISO comes with significant trade-offs: Ghost Spectre Windows 7 Superlite
If you have an old laptop with 2GB or 4GB of RAM and a mechanical hard drive, this OS can make the machine feel "snappy" again. It typically consumes less than 500MB–800MB of RAM