August 12, 1999

This supplement to the Ontario Energy Board ("Board") Staff Proposed Electric Distribution Rate Handbook (June 30, 1999) provides clarification and further details on the following:
  • Calculation of the market-based rate of return (Section S-1)

  • The use of Table 4-2 of the draft Rate Handbook, ROE Impacts of Varying Productivity Performance (Earnings Caps). This includes a proposal for the treatment of overearnings, in the event that a utility exceeds its selected ROE Ceiling in any given year (Section S-2)

  • An effective date is proposed for the change in treatment of contributed capital (Section S-3)

  • The use of actual line losses, where a utility has such information, in the unbundling of rates is clarified (Section S-4)

As with the proposals in the draft Rate Handbook, the proposals contained in this supplement are Board Staff proposals and, as such, are subject to comment by interested parties and change by the Board.


Several clarifications are necessary in regards to the market-based rate of return adjustment. These include:
  • The actual formula used to calculate the market based rate of return adjustment

  • Calculation of the rate base employed in the formula

  • The treatment of tax effects on contributed capital

  • Calculation of the target return on equity

S-1.1 Formula for Calculating the Market Based Rate of Return

Section 3.3.3 of the draft Rate Handbook provides a formula for the calculation of market-based rate of return. This supplement provides two clarifications on the formula. First, the formula has been adjusted to convert the historic return on capital used for the contributed capital portion of the equation to a before tax basis. Second, the formula now provides the revenue requirement associated with a market based rate of return. Since utilities are currently earning a return (be it negative or positive), a second formula is used to calculate the incremental amount to be included in rates associated with the start of a market based rate of return.

The reorganized formula is as follows:

This equation provides the total revenue requirement associated with the return on capital, debt expense, and income-based taxes. The first line calculates the net rate base to which the market-based rate of return is applied. The second line calculates the effective return on equity (grossed up for taxes) and the allowance for long-term interest payments. The third line calculates the increment to revenue requirements associated with providing the historical average (1994-1999) return on capital as well as making a provision for taxes associated with such a return.

In order to determine the additional revenue that a utility must collect in its initial PBR rates, in order to avail itself of the maximum adjustment for market-based rates, the return on capital that the utility earned during 1999 is subtracted from the MBRR value determined above as follows: Additional Revenue Required to Move to MBRR = MBRR (1999 Rate Base X ROK99) (1-2)

S-1.2 Definition of Rate Base

The rate base is the net fixed assets (average of year-start and year-end) plus a working capital allowance.

Net fixed assets is the total fixed assets (accounts 1600 through 2075 of the Board's Uniform System of Accounts) minus the total accumulated amortization (accounts 2100 through 2180). The proposed working capital allowance to be included in the rate base for first generation PBR is 15% of the sum of the cost of power and controllable expenses. This accounts for approximately 2-months of cost of power and 1 months of controllable expenses(1) and results in approximately similar levels to that allowed under the regulation by Ontario Hydro in the past. The working capital allowance component for the cost of power may need to be adjusted for market opening to ensure consistency with the Retail Settlement Code, in which case the utility may file for such a change as a transition cost after market opening.

A more rigorous method involving tracing of cash flow (e.g. lead-lag studies) and periodic asset valuation (e.g. monthly averages) will be considered for second generation PBR.

S-1.3 Treatment of Tax Effects on Contributed Capital

As noted in the MBRR equation (1-1) above, the return on contributed capital is now proposed to be grossed-up for the effect of PILs (payments in lieu of taxes). Utilities will use the effective tax rates to adjust rates for the tax impacts of the market-based rate of return on income taxes.

S-1.4 Calculation of the Target Return on Equity

In the draft Rate Handbook, Staff showed a 9.75% return on equity as a placeholder. It should be noted that Staff intended this target ROE to be a placeholder. The proposal is to use the methodology currently employed in gas regulation to fix the target ROE on the basis of market conditions as they exist at the time of publication in the final rate handbook. A description of the determination of the Regulatory ROE for electricity distributors in Ontario is provided in Section 5 of Dr. Cannon's December 1998 paper(2).


S-2.1 TABLE 4-2

An Excel spreadsheet that drives the analysis used to derive Table 4.2 is provided on this Web site and is named Table 4_2.


In the draft Rate Handbook, Table 4-1 provided options for pairs of Productivity Factors and associated ROE Ceilings.

The Initial ROE Ceilings for the PBR options would be set as:


Selection Productivity Factor
(annual percent change)
ROE Ceiling

In Table 4-1 of the draft Rate Handbook, the assumed MBRR was 9.75%, based on the analysis by Dr. William Cannon in 1998.(3) The actual MBRR to be used for determining the ROE Ceilings at the onset of PBR will be set by the OEB to reflect economic conditions closer to the market start. It is proposed that it be established coincident with the setting of initial rates. It is proposed that the ROE ceilings for the PBR term be annually indexed to reflect changes in the price of capital.


The test to determine if the actual ROE is in compliance annually is:

    Actual Net Income / Deemed Equity = Selected ROE Ceiling (2-1)

    Deemed Equity = Deemed CER X Rate Base

    Deemed CER varies by the size of the distribution utility, and is taken from Table 3.1 of the draft Rate Handbook.

If the condition is not met, the utility has exceeded its ROE Ceiling (overearned). Earnings above the ceiling will be reduced as described in the following section.


In the event that a distribution utility earns, in any given year, an ROE greater than the Ceiling of the PF((4))/ROE option that it selected at the outset of the PBR term, it is considered to have overearned. In such a case, the allowed ROE is capped at the ceiling; the difference between the actual ROE and the Ceiling, known as the overearning, is to be returned to ratepayers.

It is proposed that overearnings be reduced according to the following priorities:
  1. If the distribution utility has existent Z-factors, transition costs, or other extraordinary costs that are being allowed by the Board in the price cap formula, the overearnings would be first used to reduce these additional costs.

  2. If there are no such extraordinary costs, or if there is any remaining overearnings after reducing existent extraordinary costs, then the overearnings should be returned to ratepayers as a one-time rebate at the end of the year. The amount rebated to each customer would be proportional to each customer's annual distribution charges (excluding charges for Standard Supply Service).

Using overearnings to reduce rates is not considered optimal. The overearnings may be a one time event; incorporation of it into rates could result in a permanent rate reduction for subsequent price cap adjustments unless a true-up is done the following year (i.e. while the overearnings reduce rates in the next year, the base rates for the following year are readjusted to remove the overearnings component prior to calculating that year's price cap adjustments). This latter approach would seem overly burdensome.


The proposed effective date for changing the treatment of Contributed Capital would be January 1, 2000. Contributed Capital collected after that date would no longer be allowed to earn a rate of return. See also Section 3.3.2 of the draft Rate Handbook.


In the unbundling of rates, where a distribution utility has its own data on large-use line losses, this data should be used to derive unbundled rates. The 1% line loss presented in Appendix A of the draft Rate Handbook is a default value that should be used in the absence of actual line loss data.

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(1)Controllable expenses are the sum of Operations and Maintenance, Billing and Collection, and Administration.


(2)Cannon, William T., "A Discussion Paper on the Determination of Return on Equity and Return on Rate Base for Electricity Distribution Utilities", prepared for The Ontario Energy Board, December 1998.




(4)Productivity Factor

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