Light bulb by wattage

To use this methodology set the wattage of the bulb(s) using the wattage parameter. Finally, users must choose between two ways of specifying the duration for which lighting was in use.

Lighting usage

Specifying an absolute time

To specify a single, absolute quantity of time, set this duration using the totalTimeInUse parameter. The returned value represents CO₂ emissions associated with the specified duration of lighting use, based on the emissions factors for electricity generation and consumption in the United Kingdom (this location can be overriden - see below).

Specifying regular usage

Users can alternatively specify repeated intervals of lighting usage by specifying two parameters representing a rate of lighting usage and a period under consideration. For example, users could set the number of hours per day and the total number of days. To use this approach, set the rate of lighting usage using the timePerTimePeriod parameter and the duration under consideration using the timePeriod parameter. Discover converts this specification into a total quantity of lighting (electricity) consumption and calculates the associated emissions. By default, the units for the timePerTimePeriod parameter are set to hours ('h') per day ('day'), while those of the timePeriod parameter are set to days ('day') with a default value of 365.2425 (based on Gregorian calendar). This means that, unless these default values are overridden, an annual quantity of emissions based on the number of hours of lighting used per day will be returned. It is best practice to always specify units and 'per-units', however.

Specifying multiple bulbs

Users can specify multiple light bulbs, if appropriate, although it should be noted that each must represent similar wattage and usage. This may be useful where a single light fitting contains several bulbs, or perhaps where multiple rooms or internal spaces are lit consistently. To indicate that multiple light bulbs are to be considered in the emissions calculation, set the number of light bulbs using the number parameter. Discover scales up the emissions calculation accordingly. This value is set to 1 by default.

Setting the country

By default, the emissions factor for UK grid electricity generation is used to convert lighting associated electricity consumption into a quantity of greenhouse gas emissions. However, users can specify an alternative country by setting the country name or ISO code in the country parameter. In this case, Discover will lookup the appropriate grid electricity emissions factor from this dataset. If calculations are stored using profiles, the country can be specified within the profile metadata. Users should note, however, that directly specified country parameters override any set as profile metadata.