k-value (or λ lambda value)
The k- value, otherwise known as the thermal conductivity or lambda value, of a material to lead or to resist heat transfer. When used in reference to insulation, the lower the k-value, the better the insulation.
A unit of measure equal to 1,000 watts of power expended for one hour.
Kilowatt-hours peak (kWp)
The primary unit of measurement used by the solar energy industry. Watt peak is the DC output of a PV module under conditions defined by a common standard.