An alternating current electricity power that utilises two circuits with offset phases. Two phase electricity generation has been generally replaced by 3 phase electricity generation.

A two-tariff electricity meter which records separately the electricity used during the off-peak period so that it can be billed at a lower rate.

Two-photon photovoltaic effect (TPP effect) is an energy collection method based on two-photon absorption (TPA).

A two-stroke (or two-cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during only one crankshaft revolution.