Variable-speed drive
See VSD

Vats
See tanks and vats

Vending machines
The National Union of Students has a range of useful Reducing Energy Guides covering vending machines for food and drink (both heated and cooled) including also photo booths, slot machines, and advertising signs. (Link dated 9 Jan 2013)

Ventilation losses
Pathway for heat loss from a building in which fresh air brought in to the space must be heated to the occupied temperature while air which has previously been heated is discharged. More..

Voltage optimisation
Marketing misnomer signifying reduction of mains supply voltage which results in reduced power consumption in some classes of connected equipment. More..

VRF
Variable refrigerant flow: a control regime for cooling systems in which flow and return temperatures of the circulating chilling medium are held constant with output varied by regulating the flow.

VSD
Variable-speed drive: technique for reducing the power consumed in equipment driven by synchronous electric motors. Try our on-line simulation

VT
Variable temperature (in the context of heat distribution circuits)