The fixtures I ended up using used the same bulbs and similar ballasts to the previous ones, but saved enough $$ to pay for themselves in less than a 2 year span.
How do you know this to be true?
other than believing their marketing.
usually when you replace
typical 2x2' or 2x4'
drop ceiling fixtures, restrike benefits do help
by delivering better light, but not that
savings in electricity against replacement costs.
one of the myth's of drop ceiling fixture replacement
is a savings on HVAC. it's often true you only enjoy
that if they are air return fixtures, and you use the
drop ceiling as a return. if you have separate air
return ductwork, then the fixture's heat impact on
your HVAC costs are of little consequence.
always take a "lighting engineers" advice with a grain of salt,
since his training is paid for by the fixture makers themselves,
and his bias can often cost you a lot more than you need.