The company has submitted plans to regulator Ofgem that it says will support a transition to a low carbon economy in the UK.
The investment will see inspection and maintenance work carried out on 65,000 kilometres (40,000 miles) of underground cables, 40,000 kilometres (25,000 miles) and 30,000 substations between 2015 and 2023 to improve services for 3.5 million customers in central Scotland, Merseyside and north and mid Wales.
Many of the cables and stations were built between the 1950s and 1970s, and are approaching the end of service, the company said. A focus would also be on reinforcing power lines in rural areas to prevent power cuts caused by severe weather.
If approved, it would be the largest investment by ScottishPower in its distribution network. A £2.6 billion project to improve efficiency and reliability in parts of the network started this year and will last until 2021. About £90 million of the new investment would be spent on the recruitment and training of the 2,500 people needed to make the upgrades over the eight-year period, the electricity company said.
ScottishPower Energy Networks chief executive Frank Mitchell said: "We have a unique opportunity to completely modernise our infrastructure and create a blueprint to support growth for generations to come. Millions of homes and businesses in our network areas rely on a safe and secure supply of electricity. Through high levels of maintenance, we currently have reliability on average of more than 99%.
"However, to keep driving improvements and deliver more advanced and smarter infrastructure, which will bring real benefits for customers, we need to invest significantly in our network. This £5.2 billion investment will create thousands of highly skilled jobs, as we will need a new generation of engineers and technicians to deliver the upgrades. We have already started recruiting and we are also investing in partnerships with educational establishments to encourage more people to benefit from the opportunities in our industry."
ScottishPower also said it will improve its customer services by doubling compensation payments for customers who lose power for extended periods from 2015.
Customers listed on the company's priority services register will also be automatically offered accommodation and hot food if they are without power for more than 12 hours during severe weather.