The Annual Cost of Watt vs. Newcomen Engines During the Duration of Watt’s Patent and the Threshold Price of Coal

There were multiple factors determining the decision to adopt a steam engine, as opposed to opting for other power sources. But at the most elementary level this sort of decision, as well as the choice between adopting an atmospheric type or a Watt engine, hinged on the annual operating cost a potential adopter would have to incur. Authors who have previously dealt with the subject of steam power have made extensive references to the cost components of the two engine models albeit such accounts were not systematic and comprehensive enough. This chapter will attempt to fill the void, will confirm the major importance of fuel consumption in the choice of technique, and it will take a fresh look at the so-called threshold price of coal which defined the point above which the Watt model was preferred, an atmospheric engine having the advantage when the price fell below it. The derivation of the threshold coal price will be used to explain the regional and sectoral distribution patterns of the two models.