The report by Pennsylvania-based Liberty Consulting Group was prepared for the provincial Public Utilities Board as it investigates the power failures.
Rotating and unplanned outages on the island for six days starting on Jan. 2 at one point affected up to 190,000 customers.
Liberty Consulting says a lack of power to meet customer demand was on top of a lack of maintenance work to ensure backup generation was available.
"Liberty found that a continuing and unacceptably high risk of outages from such causes remains for the 2015-2017 winter seasons."
It recommends that Newfoundland and Labrador Hydro plan its resources to meet more severe weather than it has assumed in the past.
"Liberty found that Hydro's shortage of generation capacity was exacerbated by a failure to complete planned outage work needed to ensure the availability of its full range of generating facilities as the winter began," says the 86-page report.
It says the electricity company must review its planning criteria for adding new generation capacity.
The report makes 46 recommendations in all. They advise both Newfoundland and Labrador Hydro and Newfoundland Power, the province's two major utilities, to plan by June 15 a joint "lessons learned" exercise.
Planned rotating outages on the island of Newfoundland started Jan. 2 as electricity demands spiked amid an unusual cold snap of -15 C plus wind chill. A public call to conserve energy went out that day before rolling blackouts began.
But massive unplanned blackouts Jan. 4 and 5 were blamed first on a transformer fire and then a separate breaker malfunction that threw the province's thermal power plant in Holyrood offline. Various generating equipment that might have helped make up the resulting shortfall was down for maintenance.
Energy analysts at the time compared the lack of capacity and backup systems to power failures usually seen in the developing world.
Liberty recommends the two utilities jointly craft by June 15 a public communications plan for storms, outages and other major events to inform customers and follow up.