TORONTO -- Hydro One makes its debut on the TSX today, and the $1.66 billion it raised from its underwriters makes it one of the largest initial public offerings in the last 15 years.

Here are five things to know about the power utility:

It's huge: Hydro One owns more than 150,000 kilometres of low-voltage and high-voltage transmission and distribution lines, with 290 transmission stations and 1,026 distribution and regulating stations. The system includes more than 1.4 million smart meters attached to homes and buildings across the province. The company has about 1.4 million customers and $22.6 billion in assets, making it one of the largest transmission systems in North America.

Big revenues, big profits: Hydro One made a profit of $749 million on revenues of $6.55 billion in 2014. Capital spending amounted to $1.53 billion last year. Revenue has increased by 13 per cent since 2012, and the company's net assets have increased by 15 per cent in the same period to $7.95 billion.

The sun shines on its staff: More than 4,300 employees at Hydro One and its subsidiaries made Ontario's Sunshine List of those who make more than $100,000 per year on the public dime. That's out of more than 5,700 total full-time employees. CEO Carmine Marcello was one of the top-ten best paid public employees with a salary of $745,208.25 in 2015, more than three times that of Premier Kathleen Wynne at $209,385.30. After the IPO, Hydro One salaries will no longer be disclosed on the Sunshine List.

Acquisitions: Hydro One already transmits and distributes around 97 per cent of Ontario's power, based on revenue, and the company has been growing its footprint by buying smaller distributors. In 2014, Hydro One completed its buyout of Norfolk Power and agreed to buy two other local power companies, Woodstock Hydro and Haldimand Hydro.

Communications: Hydro One's telecom subsidiary owns a 6,000-km fibre-optic network and sells capacity to telecom carriers and commercial customers. The network includes hospitals and other health care locations across Ontario.