dissenting.
Section 5(d)(1)(B) of the Pacific Northwest Electric Power Planning and Conservation Act of 1980, 94 Stat. 2697, provides:
“[T]he Administrator shall offer in accordance with subsection (g) of this section to each existing direct service *401industrial customer an initial long term contract that provides such customer an amount of power equivalent to that to which such customer is entitled under its contract dated January or April 1975 providing for the sale of ‘industrial firm power.’ ” 16 U. S. C. § 839c(d)(l)(B).
The critical question in this case is whether the contracts offered by the Administrator of the Bonneville Power Administration (BPA) pursuant to the 1980 Act are for “an amount of power equivalent to” the amount to which the direct service industrial customers (DSIs) were entitled under their 1975 contracts.
Under the 1975 contracts, 75 percent of the specified amount of power was virtually guaranteed; the “top quartile,” however, was subject to interruption at any time to meet the demands of preference customers. Thus, the actual amount of power delivered under the 1975 contracts was an amount somewhere between 75 percent and 100 percent of the amount stated in the contracts.1
Under the 1980 contracts, 100 percent of the specified amounts is virtually guaranteed. No longer is the first quartile subject to interruption at any time. The result of changing the “quality” of first quartile power is to provide the DSIs with a larger amount of power than they would have received under the 1975 contracts. That is plainly inconsistent with § 5(d)(1)(B), which indicates that the DSIs’
“contracts will provide power in amounts equal to, but not greater than, that which these companies are now entitled under existing contracts with BPA, and the terms of these contracts will require that these compa*402nies continue to supply reserves for the region.” H. R. Rep. No. 96-976, pt. 2, p. 29 (1980) (emphasis supplied).2
Thus, the new contracts do not comply with the plain language of the 1980 Act.3
*403The Court attempts to. square its holding with the language of the statute by drawing a distinction between the “quantity” of power offered and its “quality.” The Court believes that while § 5(d)(1)(B) requires the same quantity of power to be offered to DSIs as was offered in 1975, § 5(d)(1)(A) requires that the “quality” of the power be higher than under the 1975 contracts; under the 1980 Act the top quartile of power provided to DSIs is of a higher “quality” since it can be interrupted only for firm power loads. Ante, at 390-391. The proffered distinction between the “quantity” and “quality” of power is nonexistent, however. Kilowatts are fungible. Interruptibility is significant not because it affects the “quality” of power a customer receives, but because it affects the amount of power a customer receives. Under the challenged contracts DSIs receive power that is less freely inter-ruptible than it was under their 1975 contracts; hence they are now entitled to a greater “amount of power” than they were under their 1975 contracts. That result violates the plain language of § 5(d)(1)(B).
In the 1981 contracts the DSIs agreed that the second quartile of power would be subject to interruption on two contingencies that were not applicable to the second quartile *404under the 1975 contracts. They therefore argue and the Court concludes, ante, at 390-391, that since respondents do not object to the fact that the second quartile under the 1980 contracts is of a different quality than under the 1975 contracts, respondents must accept the conclusion that “quality” has a meaning different from quantity. But it was after the Act was passed that the Administrator and the DSIs agreed upon a new contract that provided the DSIs with substantially more first quartile power with a fairly remote possibility of a lesser amount of second quartile power. The net result of the trade-off is still to give the DSIs significantly greater contractual entitlements than they had under the 1975 contracts. Whatever the actual comparison between the second quartile provisions of the 1975 and 1981 contracts, this argument tells us nothing about the intent of Congress since the legislative history contains no indication that Congress was aware that it was altering the interruptibility provisions of either the first or second quartiles. To the contrary, the legislative history indicates that Congress thought it was not altering the DSIs’ entitlement to power. See n. 2, supra.
Moreover, it is questionable whether the second quartile interruptibility provisions of the 1980 Act constitute a real difference from the interruptibility provisions of the 1975 contracts with respect to that quartile. As the majority explains, ante, at 392, n. 8, the 1980 Act anticipated interruption of the second quartile only because of delayed completion or unexpectedly poor performance of generating resources or conservation measures. Prior to the 1980 Act, BPA had no authority to acquire or expand its resources; its function was merely to market power generated at dams constructed by the Army Corps of Engineers. See ante, at 386, and n. 5. Hence, the 1980 Act permits second quartile interruption only on a basis that would not have arisen under the 1975 contracts.4 Surely this relatively insignificant and some*405what esoteric modification of the second quartile provisions is less persuasive evidence of congressional intent than the plain language of the statute itself.
The language of § 5(d)(1)(A) should be of little comfort to the majority. All it says is:
“The Administrator is authorized to sell in accordance with this subsection electric power to existing direct service industrial customers. Such sales shall provide a portion of the Administrator’s reserves for firm power loads within the region.” 16 U. S. C. §839c(d)(l)(A).5
This subsection makes no reference at all to the “quality” of power to which DSIs are entitled. If this language was designed to entitle DSIs to higher “quality” power than they received under their 1975 contracts, then Congress picked a rather obtuse way of expressing the idea.
I read the subsection to mean what it says. The sales that the Administrator makes to the DSIs are part of the reserve for firm power loads.6 In the event of a shortfall, the Administrator is obligated to use top quartile DSI power to meet his firm power obligations even when there is a prefer*406ence customer seeking to purchase power; in this respect § 5(d)(1)(A) was necessary to change the law with respect to the rights of preference customers, which would otherwise have had priority even over purchasers of firm power.7 But a provision ordering the Administrator to use top quartile power as a reserve for firm loads sheds no light on the extent of his obligation to sell power to the DSIs. That obligation is governed not by § 5(d)(1)(A), but by § 5(d)(1)(B).8
Because I find nothing in the statute or in its legislative history to indicate that Congress intended to allocate a greater amount of power to the DSIs than they were entitled to receive under their 1975 contracts, I cannot square the Court’s holding with the plain language of the statute. I therefore respectfully dissent.
Apparently only about two-thirds of the first quartile load was being delivered to the DSIs during the years preceding the passage of the 1980 Act. See App. 36. Thus, it would seem that the amount of power actually delivered to those customers was approximately 91 percent of the stated contract amounts.
The passage from the Senate Report quoted by the majority ante, at 396, when read in context, is inconsistent with the majority’s conclusion that DSIs have greater protection against interruption under the 1980 Act than under their 1975 contracts:
“The power quality provided the direct-service industries is determined by the reserve obligations set forth in their contracts in order to protect service to firm loads of the Administrator. It is intended that these contracts at least provide peaking power reserves similar to those provided in the present contracts, and that the energy reserves shall include a reserve approximately equal to 25 percent of the direct service industrial load to protect firm loads for any reason, including low or critical streamflow conditions, and an additional energy reserve of approxiamtely [sic] the same amount to protect firm loads against the delayed completition [sic] or unexpectedly poor performance of reginal [sic] generating resources or conservation measures, and against the unanticipated growth of regional firm loads. One intended result of these procedures is that there will be no increase in firm power commitments to the direct service industrial customs [sic], except for technological improvements purposes.” S. Rep. No. 96-272, p. 28 (1980).
When read in light of its last sentence, this paragraph makes it clear that Congress intended that DSIs have no greater assurance against interruption than they did under their 1975 contracts. Moreover, in a rate analysis submitted to Congress by the BPA, it estimated its projected revenues under the proposed legislation by assuming that it would continue to interrupt the top quartile of DSIs’ power at the same rate that it had done so in the past, n. 1, supra, supplying from 86 to 96 percent of the DSIs’ loads, and also anticipated interruptions in the top quartile in excess of those necessary to protect firm loads. See S. Rep. No. 96-272, at 59.
To the extent that the Court relies on “deference” to the Administrator’s interpretation of the 1980 Act, ante, at 390, it must be borne in mind that what is at issue here is the agency’s construction of a statute:
“The interpretation put on the statute by the agency charged with administering it is entitled to deference, but the courts are the final authorities on issues of statutory construction. They must reject administrative constructions of a statute, whether reached by adjudication or by rulemaking, that are inconsistent with the statutory mandate or that frustrate the policy that Congress sought to implement. Accordingly, the crucial issue at *403the outset is whether the Court of Appeals correctly construed the Act.” FEC v. Democratic Senatorial Campaign Comm., 454 U. S. 27, 31-32 (1981) (citations omitted).
It is also worth noting that the Adminstrator’s interpretation of this Act has not been a model of consistency. In the BPA’s final Environmental Impact Statement, issued in December 1980, it stated that top quartile DSI power can be interrupted “[a]t any time for any period for any reason.” App. 31. Similarly, in its summary of its original draft contracts under the 1980 Act, it stated: “BPA may interrupt a portion of the DSI load, not to exceed 25 percent of the Operating Demand plus the Auxiliary Power, at any time, for any reason, and for any duration.” Id., at 74. See also n. 2, supra. In light of the lack of clarity that has characterized BPA’s position both before and after the passage of the 1980 Act, its position surely is not entitled to so much deference as to override the plain import of the words Congress enacted. See General Electric Co. v. Gilbert, 429 U. S. 125, 143 (1976).
Even if the issue would have arisen under the 1975 contracts, it is doubtful that the DSIs would have been entitled to second quartile power *405in the circumstances in which interruption is permitted under the 1980 Act; those circumstances most likely would have given rise to a commercial frustration defense permitting BPA to interrupt second quartile power to the DSIs.
Section 3(17) of the Act defines “reserves”:
“ ‘Reserves’ means the electric power needed to avert particular planning or operating shortages for the benefit of firm power customers of the Administrator (A) from resources or (B) from rights to interrupt, curtail; or otherwise withdraw, as provided by specific contract provisions, portions of the electric power supplied to customers.” 16 U. S. C. § 839a(17).
The legislative history of § 5(d)(1)(A), of which the Court makes so much, ante, at 396-397, does not demonstrate that the statute means something other than what it says. The passages from the Committee Reports on the Act quoted by the majority state that the Administrator must treat the top quartile as a reserve to protect firm loads. That he has surely done. But it does not speak to whether that quartile is interruptible to meet the needs of preference customers. See also n. 2, supra.
Prior to the passage of the 1980 Act, the Ninth Circuit had construed preference provisions to prohibit the sale of power to a private customer whenever there is a preference customer willing to buy it. See City of Santa Clara v. Andrus, 572 F. 2d 660, 670-671 (CA9), cert. denied, 439 U. S. 859 (1978); Arizona Power Pooling Assn. v. Morton, 527 F. 2d 721, 727-728 (CA9 1975), cert. denied, 425 U. S. 911 (1976).
In Part II-C of its opinion, ante, at 398-400, the Court points out that the higher rates charged to DSIs provide a subsidy for certain consumers served by investor-owned utilities, implying, I suppose, that it makes good sense to sell the DSIs more power than they received under the 1975 contracts. If Congress had wanted the Administrator to exploit the DSI market by increasing the amount of such sales, it should not have limited their share of the available supply to an “amount of power equivalent to that to which” DSIs were entitled under the 1975 contracts. And in fact the rate analysis submitted by BPA indicated that it would supply power to DSIs at the same levels as it did under the 1975 contracts. See n. 2, supra. Rather, the fact that the Administrator charged higher rates to DSIs after the 1980 Act became effective is significant only because it explains why § 5(d)(1)(B) did not simply provide that the new contracts would contain precisely the same terms and conditions as the 1975 contracts. Under the new contracts the DSIs’ entitlement to power was to be the same as under the old contracts, but the DSIs had to pay a higher price for it.