Energy-efficient bulbs for home use cost more than regular bulbs, but they save the purchaser money over time, because the lights require less electricity to operate.
(they; save; the purchaser money; T:over time; because the lights require less electricity to operate) (the lights; require; less electricity; to operate) (less electricity; to operate; )
they the lights less electricity
save require to operate
the purchaser money T:over time because the lights require less electricity to operate
less electricity to operate