At the time, 95% of the main heating systems installed in properties by Nest and 98% by Arbed were fossil fuel based.
Ar y pryd, roedd 95% o'r prif systemau gwresogi a oedd wedi cael eu gosod mewn eiddo gan Nyth, a 98% o'r rhai a oedd wedi cael eu gosod gan Arbed, yn defnyddio tanwydd ffosil.