If electric, 50 amperes (5)
I believe the answer is:
lamps
'if electric' is the definition.
I can't judge whether this defines the answer.
'50 amperes' is the wordplay.
'50' becomes 'l' ('L' can be a synonym of '50').
'amperes' becomes 'amps' ('amp' can be a synonym of 'ampere').
'l'+'amps'='LAMPS'
Can you help me to learn more?
(Other definitions for lamps that I've seen before include "Devices for giving light" , "Lights" , "light fittings" .)