The weight of the load is (mass) x (gravity).
The work done to lift it is (weight) x (distance) = (mass) x (gravity) x (distance)
The power is (work)/(time) =
(mass) x (gravity) x (distance) / (time) =
(500 kg) x (9.8 m/s²) x (12 m) / (1 sec) =
(500 x 9.8 x 12 / 1) (kg-m / sec²) (m) / (sec) =
(500 x 9.8 x 12 / 1) newton - meter / sec =
(500 x 9.8 x 12 / 1) joule / sec =
58,800 watts
= 58.8 kW
= about 78.8 horsepower