From the Ontario Governments Ministry of Revenue web site:
"GRC Rates:
Effective January 1, 2001, the current GRC rates for both property tax components are graduated based on the annual generation of a station as follows:
1. 2.5 per cent on gross revenue from the first 50 gigawatt hours of annual generation from the generating station.
2. 4.5 per cent on gross revenue from annual generation from the generating station above 50 gigawatt hours up to and including 400 gigawatt hours.
3. 6.0 per cent on gross revenue from annual generation from the generating station above 400 gigawatt hours up to and including 700 gigawatt hours.
4. 26.5 per cent on gross revenue from annual generation from the generating station above 700 gigawatt hours.

Every station owner benefits from the lower rates on the gross revenue from the first 700 gigawatt hours of annual generation for each station. The GRC water rental charge rate is fixed at 9.5% of a station's gross revenue from annual generation. "

The MNR Policy WR 3.02.01 only provides a 10 year holiday from the GRC rates for both property tax components. It does not provide relief from the 9.5% water rental charge which is applied against a stations gross revenue.

The OPA working assumption that waterpower projects do not have to pay for the water is incorrect. Waterpower projects must pay 9.5% of gross revenue for water rental, as well as the GRC rates for both property tax components after the initial 10 year grace period provided by the MNR has expired.