Not sure about the assumption of 1c per Wh, easier just to work...

Not sure about the assumption of 1c per Wh, easier just to work with the MWh price.

Wholesale flat swap price for Queensland is between $50 to $60 per MWh (slide 10 of recent AGL presentation), throughout the day the MWh price varies between about $20 to $95 per MWh (slide 18 of recent GNX presentation) which is the basis of the pumped water storage arbitrage opportunity.

First stage of solar (50MW) produces 130,000 MWh per annum.

Based on these figures the sales revenue per annum would be 130,000 MWh x $55 = 7.15m, plus the cash from the Renewable Energy Certificates (Large-scale Generation Certificates). These fluctuate a bit but are currently worth $80 per certificate, as I understand it one certificate equates to one MWh. 130,000 MWh x $80 = 10.4m.
Total annual revenue 17.45m.

If they go ahead with expansion to 150MW then figures for annual solar revenue can be multiplied by 3.

Re the $95 figure in the AGL presentation, I don't think this is annualised running costs, it is headed as "Renewable generation long run cost". I'd say this is AGL's overall cost (Capex - grants + Opex) for a MWh.

Anyway still an interesting company with proven management, I like the arbitrage and crossover with the certificates - sell the solar to get the revenue from the certificates, then buy back coal generated power at $20 per MWh to pump up to the top dam, letting the water go when the power generated can be sold for above $60 MWh. Question is whether they can get certificates for the hydro as well, does it get classified as renewable even though the water was pumped up by coal power?

Apparently the energy efficiency of pumped water storage is typically between 70-80%.

So for a rough idea of pumped water storage revenue let's start with 50% of nameplate of 450MW operating 5 hours a day = 1125MWh per day * 365 = 410,625 MWh per year.
Purchase 410,625 MWh @ ~$25 per MWh = 10.26m.
Power return of 410,625 MWh x 75% = 307,968.75 MWh
Sell 307,068.75 @ ~$65 per MWh = 19.96m
Annual revenue = 19.96m - 10.26m = 9.7m (at only 50%)

If they get certificates for it the figure can be roughly doubled, and if they operate at full capacity it can be doubled again.