This invention relates to an electricity generator comprising a pressure chamber having a releasably sealable air vent, a liquid supply, a sump tank configured to deliver liquid to the pressure chamber and a turbine. The electricity generator further comprises a piping network including an upright liquid conduit configured to deliver water from the pressure chamber through the turbine and back to the sump tank, a pressurized air supply operable to pressurize air in the pressure chamber, a plurality of valves, and a controller to operate the plurality of valves. In use, a small amount of air may be used to efficiently move a large body of water which in turn is used to power a turbine. The electricity generated by the turbine may be harvested and subsequently used, thereby reducing electricity spend. The installation is compact and may be installed in a factory or other installation where electricity requirement/spend are high.