Power grid had 'shallow' lack of reserve capacity on Monday afternoon but grid operator expects electricity system to cope with more hot weather

Sydney recorded its hottest March day for two years on Monday, and further hot temperatures are expected today and tomorrow, with maximums between 27 degrees and 32 degrees between today and Monday.

Although Tuesday's temperatures were almost as hot as Monday's - Newcastle was recording a mid-afternoon temperature of 35 degrees compared to a Monday peak of 37 degrees - the impact on the grid was nowhere near as severe, according to data from the Australian Energy Market Operator, AEMO.

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A spokesperson for AEMO said electricity usage in NSW peaked at 7pm with demand of 13,136 megawatts, which was 963 megawatts or 7.9 per cent higher than the previous record of 12,173 megawatts set on March 9, 2016.

AEMO said the mix of generation sources at the time of the 7pm peak was: black coal (52.7 per cent), hydro (16.2 per cent), gas (9.4 per cent), wind (6.1 per cent), grid-scale solar (5.8 per cent) and other (9.8 per cent).

For the 48 hours to 3pm yesterday, coal had provided 68 per cent of the state's power, with solar 13 per cent, wind 12 per cent, hydro five per cent and gas two per cent.

The AEMO spokesperson confirmed that an "actual lack of reserve level two" market notice had been sent out on Monday, calling for "an immediate market response" from power suppliers, saying "an insufficient market response may require AEMO to implement an AEMO intervention event".

"The forecast capacity reserve requirement is 700 megawatts (and) the minimum capacity reserve available is 611 megawatts," said the market notice for the half-hour period between 5pm and 5.30pm on Monday.

The AEMO spokesperson described the situation as a "shallow LOR2", and said the market response meant AEMO did not need to take action to forcibly reduce power consumption, as it was able to do under certain circumstances.

Although the wholesale price of electricity peaked briefly at above $1400 a megawatt-hour at about 6.30pm on Monday, it was nowhere near the market cap of $15,500.

Electricity transmission company Ausgrid did have to work to restore supply to about 11,000 homes in Sydney but said the outages were a result of a number of isolated incidents, and not the heat.

Although the grid eventually coped with Monday's heatwave, the remaining three units of AGL's Liddell power station are set to close next month, taking a potential maximum of 1500 megawatts out of the system.

The Hunter's hot weather this week has been driven by hot north-westerly winds, which blew throughout Monday and picked up again yesterday morning. The offshore wind continued until mid-afternoon, when a light but cooler nor-east wind began to bring down temperatures on the coast.

Temperatures at Singleton and Muswellbrook are forecast to be a few degrees higher than on the coast, with northwesterly winds to continue.

A severe weather warning remains for damaging winds on parts of the south coast, Southern Tablelands, Snowy Mountains, Canberra and South West Slopes.

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