kWhm2år

KWhm2år, written as kWh/m^2·yr, is the unit kilowatt-hours per square meter per year. It expresses an amount of energy tied to a unit area over a one-year period. The unit is used whenever energy is reported relative to surface area, allowing comparisons across different sizes and locations.

There are two common contexts for kWh/m^2·yr. In solar energy resource assessment, it denotes the annual energy that would be incident on a surface per square meter, for a given orientation and tilt, typically on horizontal or tilted surfaces. In building energy performance, it denotes the annual energy use or demand per unit floor area, including heating, cooling, ventilation, hot water, and electricity, as a metric of energy efficiency or consumption.

Calculation and data sources vary by context. Solar data come from meteorological measurements or solar radiation models and are reported as energy per area per year. Building energy figures are derived from energy models, simulations, or actual energy bills and are often used in certification schemes and building codes. Values depend strongly on location, climate, orientation, and building design.

Common conversions include 1 kWh/m^2·yr = 3.6 MJ/m^2·yr. In practice, annual solar irradiance on a site typically ranges from about 800 to 2400 kWh/m^2·yr depending on latitude and climate, while building energy use per area can span from well below 100 kWh/m^2·yr for very efficient buildings to several hundred kWh/m^2·yr for conventional older buildings.