Optimum start is a control strategy that initializes building conditioning (heating or cooling) prior to occupancy based on a building's computerized controller
In HVAC, optimum stop is a control strategy that turns off the cooling compressor (or heating equipment) but keeps ventilating the building during the time period when occupants are getting ready to leave. Depending on the building, this can be as much as 1.5 hours to 15 minutes before the building becomes unoccupied. The building temperature drifts slightly during this time period. Optimum stop can be used in a building that uses optimum start, but the two strategies are completely separate and not dependent on each other (as is a common misconception)
A receptacle load is the amount of load produced by a device plugged into a receptacle (often called plug loads). Receptacle loads typically produce heat and consume electricity
The setpoint temperature is the temperature at which a zone is controlled during occupied hours. In LEED buildings, it is required that there is a 5 degree difference between cooling and heating setpoints (i.e. if the heating setpoint is 70 degrees, the cooling setpoint must by 75 degrees)
Simple payback is a number, typically in years, for the time it takes to pay for an initial investment. It does not account for the time value of money. Equation: (Initial Investment Cost)/(Cost savings per year)