The company has already signalled that there will be no more special dividends while it faces the challenge posed by the planned closure of its biggest customer, the Tiwai Point aluminium smelter, next August.
Tiwai consumes about 13 per cent of New Zealand's power output.
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The company said it had deferred the $400m Harapaki wind farm project in the Hawke's Bay because of Tiwai's planned closure.
Over the year, Meridian generated a record amount of electricity in New Zealand, supported by improved wind farm availability and lake inflows that were 115 per cent of average.
Chief executive Neal Barclay said 2020 was another successful year for Meridian.
"But there are significant challenges on the horizon, particularly the global impact of the Covid-19 pandemic and, the closure of the Tīwai Point Aluminum Smelter," he said.
"These changes will affect the way in which we operate our business and we are confident we have the team and the strategies to manage through these uncertain times."
The volume of electricity sold to customers increased by 18 per cent and 24 per cent in New Zealand and Australia respectively.
Customer numbers were also well up in both countries.
Just after financial year's end, Tiwai's majority owner Rio Tinto announced it was terminating its electricity supply contract with Meridian Energy.
Meridian worked with the industry to offer the smelter a deal worth $50m a year from day one, increasing to close to $60m-$70m over the next three years.
"Despite our efforts the owners have made the decision to terminate the electricity supply agreement with Meridian in August 2021 and close the smelter."
Meridian had engaged with Rio on the possibility of extending the closure period from one year to four years.
"At this stage we are not aware if an extended closure proposition is acceptable to them," Barclay said.
"Rio Tinto's decision is hugely disappointing for the Smelter workforce and the Southland community and this outcome is not one that Meridian would have chosen.
"However, given the age of the facility, a decision to close was probably inevitable within this next decade in any event."
Barclay said Tiwai closing created an "imperative" for New Zealand to use it as an opportunity to further reduce carbon emissions and its reliance on fossil fuels.
On Harapaki, Barclay said: "While the business case for Harapaki is very sound, the market needs time to adjust to Rio Tinto's decision to exit New Zealand. We're still confident that we'll build Harapaki in the future."
The Harapaki wind farm is in the Maungaharuru Range in Hawke's Bay, about 35km northwest of Napier.
The site consists of two adjacent wind farm sites - Hawke's Bay Wind Farm and Titiokura Wind Farm - that were originally consented in 2006 to Hawke's Bay Wind Farm Ltd and Unison Network Ltd.
In 2010, Meridian purchased the consents for both sites.
As of last year, Meridian has approval from the Hastings District Council to construct and commission a 41-turbine wind farm.
The wind farm would have had the capacity to power around 70,000 homes.
Meridian shares last traded at $5.03, down 9c from Tuesday's close, having gained 9.6 per cent over the past 12 months.
