Part L (UK) Section of Building Regulations dealing with conservation of fuel and power. Read article by John Field. Performance deficit The excess quantity of excess consumed in a given period, relative to what would have been required if the building or process in question had been operated at best achievable efficiency Performance indicator, energy Usually a single numerical value intended to convey how energy-efficient a process or building is in operation. The attributes of a well-chosen energy performance indicator (EnPI) are that (a) it only changes when something is done which alters energy performance; (b) it changes by an amount consistent with the change in energy performance and in a consistent direction; and (c) it is immune to changes in factors (weather, production, etc) which are known to cause changes in consumption. These requirements are met for example by the Energy performance coefficient (formerly "Energy Intensity Coefficient"). Plug-in small appliance meters More.. Power factor Ratio, between 0 and 1, between the real power delivered in an AC circuit and the power which would be delivered if current and voltage were in phase. Click here here for an explanatory video. Power Strictly, the rate of generation delivery or conversion of energy and expressed in kilowatts, horsepower, etc. Click here for an on-line tool for estimating power requirement by step test. Price, energy Follow this link for UK Goverment quarterly energy price bulletins which includes comparisons of fuel prices in the EU and G7 countries Profile logger Instrument for recording variations in power consumption over the course of one or more days, for instance at 30-minute intervals Psychrometric chart Diagram showing the properties of moist air, with the horizontal axis showing dry-bulb temperature and the vertical axis the humidity ratio (grams of moisture per kg of dry air). Assorted curves, lines and external scales are provided such that at any point on the chart parameters such as enthalpy, relative humidity, dewpoint, vapour pressure and wet-bulb temperature can be read off. A downloadable version is provided here. PV Photovoltaic; generating electricity directly from light, usually sunshine.