Calculation of reduced tax rate

If a unit has been incapable of generating electricity for eighteen consecutive months, the tax on that unit for taxable periods beginning after the eighteenth month must be reduced by the ratio that the estimated cost to repair bears to the original cost of the unit. When the unit is again capable of generating electricity, the reduced tax rate must be recalculated, using the ratio that the cost to repair bears to the original cost of the unit. Taxes for all taxing periods during which the reduced rate was in effect must be recalculated, and adjustments for underpayments or overpayments made. The full tax rate will be in effect for the month in which the unit is again capable of generating electricity.