Morgan Est has been selected by power company E.ON for a 10-year electrical distribution framework worth an estimated £500m.
The contract for Morgan Sindall's infrastructure business covers E.ON's Central Networks eastern region.
The programme of works will include capital asset replacement and reinforcement to overhead lines and underground cables up to 33kV.
In addition, Morgan Est will carry out works to replace distribution plant and remedial work programmes, which include building, civil engineering works and the inspection and maintenance of the distribution network up to 132kV.
Work will begin this month.
Paul Smith, Chief Executive of Morgan Sindall plc, said: "This is a very important win for our Infrastructure Services division, building on the strong relationship we have developed with E.ON over the past decade. We see a number of opportunities in the energy sector and our position within this market leaves us well placed to benefit from this trend."