Fodd bynnag, mae cyfran helaeth o ynni Cymru yn dod o danwydd ffosil o hyd a cheir cyfran uchel o ddiwydiant trwm y DU yma. Mae gan lawer o gartrefi waliau solid, gan eu gwneud yn fwy costus i’w hinswleiddio, ac nid oes gan lawer o gartrefi gyswllt â’r grid.  Gall natur wledig rhannau mawr o Gymru wneud teithio sy’n ecogyfeillgar yn fwy anodd.
However, a large proportion of Wales’ energy still comes from fossil fuels, while a high share of the UK’s heavy industry is based here. Many homes have solid walls, making them more costly to insulate, and many homes are ‘off-grid’. The rural nature of much of Wales can make environmentally-friendly travel more difficult.