For real situation requirement, the emergency backup just need remain 20% of original lumens.
It's for emergency case, no need remain 100% lumen. Actually, based on maintain 20% Lumen Standard, 25W Emergency Backup could match at most 125W LED lamps. By the Way, Philip Bodine Emergency Backup has at most 23W option. OKT have 8W/12W/25W option.