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Here are calculation explanations for a selection of cards in the Housing category.

This category includes the greenhouse gas emissions from:

– Production of electricity, and energy for heating.

– For refrigerators, freezers, cooking, dishwashing, laundry, etc., both the manufacture and use of the appliances are included in most cases.

The greenhouse gas emissions from the following activities are not included:

– Construction and maintenance of houses and apartments.


We have assumed that the water in the shower holds 39 °C.

The efficiency of the fossil gas boiler is measured as the ratio between the useful output (heat), and the input (fossil gas). We used the following average efficiencies: 

– Fossil gas boiler in the UK: 82.5% based on DECC (2014).

– Fossil gas boiler in the US: 85% based on STRATEGO (2015).

The conversion efficiency of a boiler or furnace cannot be more than 100%. The air conditioner, however, functions in a different way. Instead of burning fuel to create heat (like the boiler), it uses electricity to move heat from one place to another (indoor to outdoor, in the case with cooling). Technically, an air conditioner works as a heat pump, and can have an efficiency above 100%. We assumed that the US air conditioner has a conversion efficiency of 310% based on STRATEGO (2015). This means that for every unit of electricity supplied, the air conditioner transfers more than three times as much heat from inside to outside the house, thereby cooling the house. 

The emission value is negative since it refers to the avoided emissions that are saved by using solar panels. The value on the card has been calculated as the difference between the emissions from using the average power mix in each country/region and the emissions from generating electricity using solar panels.