Electricity supply was affected in the state around 2.30 AM and lasted nearly nine hours.
The technical malfunction has been removed and normal power supply has been restored, an electricity board official said.
Power was restored around 10.30 AM in some parts of the state while it was normalised in other parts by noon.
Lack of electricity affected the pumping of water at stations which could result in curtailing water supply tomorrow, Shimla Municipal Corporation authorities said.
Power generation in all major hydro-power projects also came to a halt as the projects were shut down. The 1500 MW Nathpa-Jhakri hydropower project resumed power generation after seven hours.
Banking services were affected and mobile coverage remained erratic.