By 1800, the firm Boulton & Watt had constructed 496 engines, with 164 driving reciprocating pumps, 24 serving blast furnaces, and 308 powering mill machinery; most of the engines generated from 5 to 10 hp. An estimate of the total power that could be produced by all these engines was about 11,200 hp. This was still only a small fraction of the total power generating capacity in Britain by waterwheels (120,000 hp) and by windmills (15,000 hp); however, water and wind power were seasonably variable. Newcomen and other steam engines generated at the same time about 24,000 hp.