These schemes have often been targeted at the most vulnerable in society, who may be less able to deal with problems if an installation goes wrong.
Mae llawer o'r cynlluniau hyn yn cael eu targedu er lles y mwyaf bregus mewn cymdeithas, a fydd efallai'n llai abl i ddelio â phroblemau pan fydd pethau'n mynd o chwith.