The maximum freight charge per mile for the same wagon load was 20 d. Room heating was normally better done by charcoal braziers than hypocausts.But hypocausts did allow them to exploit any poor-quality smoky fuels like straw, vine prunings and small wood locally available.

All technology uses energy to transform the material into a desirable object or uses some form of mechanics combined with another form to make something better.

The cheaper energy is, the wider the class of technologies that are considered economic.

This is why technological history can be seen as a succession of ages defined by energy type i.e. The Romans used water power, and watermills were common throughout the Empire, especially to the end of the 1st century AD.

They were used for cereals milling, sawing timber and crushing ore. There were huge reserves of wood, peat and coal in the Roman Empire, but they were all in the wrong place.

Wood could be floated down rivers to the major urban centres but otherwise it was a very poor fuel, being heavy for its caloric value.

If this was improved by being processed into charcoal, it was bulky. Diocletian's Price Edict can give us a glimpse of the economics of transporting wood.

The maximum price of a wagon load of 1,200 lbs of wood was 150 d.(denari).

Roman technology is the engineering practice which supported Roman civilization and made the expansion of Roman commerce and Roman military possible for over a millennium (753 BC–476 AD).

The Roman Empire was one of the most technologically advanced civilizations of antiquity, with some of the more advanced concepts and inventions forgotten during the turbulent eras of Late Antiquity and the early Middle Ages.