On Dec 24, 3:29*pm, wrote:

According to Wikipedia, coal is about 6.67 kWh/kg.

A lot depends on what sort of coal it is.

Also according to Wikipedia anthracite has an LHV of 33MJ/kg which
gives 9.17kWh/kg.

I doubt Aga owners will be feeding their beast on 'value' brown coal,
more like /Finest/ smokeless or anthracite ))

cheers,
Pete.