Do I need ECC RAM for a home NAS build?

Probably not. For a home NAS with movies, backups, or family photos, regular RAM is fine. ZFS checksums everything and catches single-bit errors during scrubs. The real cost is the server-grade motherboard and CPU needed for ECC support, which adds $200–$400—money better spent on more storage or a better UPS. Only go ECC if your data is truly irreplaceable or you’re running a production server.