The developers submitted plans to the PSC in November 2016 as part of an application process. It had been expected the PSC would only approve one of the two projects.
US Wind won the US' third federal lease round in August 2014 for a 323-square-kilometre site located about 18km off the coast of Ocean City, Maryland. The 248MW project is due online from 2020.
Deepwater Wind's 120MW Skipkjack site is located just north of US Wind's and 30km northeast of Ocean City and completion is expected in 2022.
The PSC awarded the Offshore Renewable Energy Credit (ORECs) at a levelised price of $131.93/MWh.
"The approval today of the nation's first large-scale offshore wind projects brings to fruition the General Assembly's efforts to establish Maryland as a regional hub for this burgeoning industry," said Kevin Hughes, the Commission Chairman.
"We have taken great care to ensure that this decision maximizes economic and environmental benefits to the state while minimizing costs to Maryland ratepayers," Hughes added.
The PSC said the ORECs would add less than $1.40 to residents' monthly electricity bills once the projects start generating electricity.
As part of the approval terms, the PSC said the developers should create almost 5,000 direct jobs in the state, pass 80% of any cost savings to residents and contribute to a local development fund.
There must also be investment in a steel fabrication plant in Maryland, and the state's port facilities in either Baltimore or Ocean City must be utilised, the PSC said.
US Wind and Deepwater Wind have until 25 May to accept the conditions.
"US Wind wants to thank the PSC for this favorable decision, as well as governor Larry Hogan and commerce secretary Mike Gill for showing that Maryland is truly 'Open for Business.' Maryland is now the undisputed national leader for offshore wind," said US Wind director of project development, Paul Rich.
Maryland has a renewable energy portfolio standard, which requires the state to source 25% of its electricity from renewable energy sources by 2020.