heat content is recovered by heating the compressed air entering the recuperator in line 4 the cooled exhaust gas leaves the recuperator in the exhaust gas duct 12 the compressor 3 and the turbine 10 are both mounted onto a common shaft 17 which also carries a high speed electrical generator unit 18 rotation of the turbine 10 induced by the gas flow in line 9 also rotates the generator 18 to provide electrical power in the conventional recuperated microturbine unit the exhaust gas is usually vented directly to a suitable stack 17 as indicated by the chain line 12 a in some units the exhaust gas is passed through a second heat recovery unit for example to provide hot air for space heating and then vented to a suitable stack in a recuperated microturbine unit according to this invention the exhaust gas leaves the recuperator 5 in the exhaust duct 12 and passes to the duct burner unit 13 in the duct burner 13 more of the oxygen in the exhaust gas in the exhaust gas duct 12 is burnt with further fuel in line 14 to raise the exhaust gas temperature the heated exhaust gas leaves the burner in a continuation 15 of the exhaust gas duct after passing through the heat exchanger 16 the exhaust gas is vented through a suitable stack 17 a second fluid also flows through the heat exchanger 16 entering in line 20 and leaving in line.