On March 31, 1982, Southern California Edison applied to the Federal Energy Regulatory Commission for a rate increase. Five California cities, wholesale customers of Edison, intervened in opposition. 1 When a utility files a new rate schedule with FERC (formerly the Federal Power Commission), the Commission can take one of three actions:

FERC has 60 days to decide which course to follow. 16 U.S.C. § 824d(d) (West Supp. 1983); Indiana & Michigan Electric Co. v. FPC, 502 F.2d 336, 341 (D.C.Cir.1974), cert. denied, 420 U.S. 946 , 95 S.Ct. 1326 , 43 L.Ed.2d 424 (1975).

In this case FERC chose the second of the three options. On May 28, 1982, the Commission suspended step one of the proposed rate increase, the portion at issue in this appeal, for one day only. FERC also scheduled a hearing on the merits of Edison’s proposal and preserved the cities’ right to a refund if the rates were ultimately found excessive. Southern California Edison Co., 19 FERC ¶ 61,209 (May 28, 1982). In fixing the suspension at one day, FERC purported to follow the policy set out in West Texas Utilities Co., 18 FERC ¶ 61,189 (Feb. 26, 1982).

The cities petitioned for rehearing claiming that Edison’s filing should have received the maximum, five-month suspension. Their petition was denied on August 2, 1982 and they filed a timely appeal.

The cities raise several issues, two of which merit extended discussion: 1) whether FERC’s West Texas policy ought to have been adopted via rulemaking, and 2) whether FERC applied the policy improperly in this case. We hold that the West Texas policy was properly adopted and decline to review its application to Edison’s rate proposal.

A. The recent history of FERC’s suspension policy

West Texas was the culmination of three years of doctrinal development triggered by the District of Columbia Circuit’s opinion in Connecticut Light and Power v. FERC, 627 F.2d 467 (1980). There the court criticized FERC’s inadequate explanation of its suspension decisions and remanded for the Commission to “establish standards for the exercise of its discretion,” either by rule-making or in “individual cases.” Id. at 473 . FERC responded by announcing in Kansas City Power & Light Co., 12 FERC ¶ 61,118 (Aug. 1, 1980), that:

Identical language appears in subsequent FERC opinions. See, e.g., Alabama Power Co., 12 FERC ¶ 61,210 (Aug. 29, 1980); Boston Edison Co., 12 FERC ¶ 61,211 (Aug. 29, 1980).

*659 Since Kansas City Power and Light, FERC has found “particular circumstances” justifying a one-day suspension when preliminary analysis suggests that the proposed rates are not excessive. Cleveland Electric Illuminating Co., 12 FERC ¶ 61,184 (Aug. 22, 1980); Indiana & Michigan Electric Co., 13 FERC ¶ 61,241 (Dec. 18, 1980); Appalachian Power Co., 14 FERC ¶ 61,027 (Jan. 16, 1981). This consistent exception to the general policy of five-month suspensions was formalized in West Texas Utilities Co., 18 FERC ¶ 61,189 (Feb. 26, 1982). FERC not only made clear that the exception would continue to hold, but clarified its meaning:

No court has yet ruled on the legality of the West Texas policy, but Judge Robinson of the District of Columbia Circuit cited it approvingly in his concurrence in Southern California Edison Co. v. FERC, 686 F.2d 43 , 47-8 (D.C.Cir.1982).

B. Adjudication and rulemaking by agencies

Administrative agencies are free to announce new principles during adjudication. NLRB v. Bell Aerospace Co., 416 U.S. 267, 290-5 , 94 S.Ct. 1757, 1769-72 , 40 L.Ed.2d 134 (1974); Saavedra v. Donovan, 700 F.2d 496, 499 (9th Cir.1983). Two exceptions qualify this general proposition. First, agencies may not impose undue hardship by suddenly changing direction, to the detriment of those who have relied on past policy. See Ruangswang v. INS, 591 F.2d 39 (9th Cir.1978), where the plaintiff qualified as an investor under the letter of the regulation, but faced deportation because of an adjudicatory opinion that further restricted the definition of investor status. The adjudicatory opinion cited by the INS was published after Mrs. Ruangswang had made her initial investment. The present case stands in sharp contrast. The cities have not taken any particular action in reliance on FERC’s pre-West Texas suspension policy. Also, West Texas did not abruptly change but rather strengthened and clarified a previously recognized exception to the general rule of five-month suspensions. Further, even if the cities had relied on prior policy and even if West Texas were a radical policy change, the hardship would be minimal because FERC preserved the cities’ right to a refund.

The second limiting doctrine is that agencies may not use adjudication to circumvent the Administrative Procedure Act’s rule-making procedures. NLRB v. Wyman-Gordon Co., 394 U.S. 759 , 89 S.Ct. 1426 , 22 L.Ed.2d 709 (1969); Montgomery Ward & Co. v. FTC, 691 F.2d 1322 (9th Cir.1982); Patel v. INS, 638 F.2d 1199 (9th Cir.1980); Ruangswang, supra. This exception is inapplicable to the present case. FERC has not used West Texas to amend a recently adopted rule, as in Montgomery Ward, Patel, and Ruangswang , or to supplant a pending rule-making proceeding, as in Ford Motor Co. v. FTC, 673 F.2d 1008 (9th Cir.1981), ce rt. denied, 459 U.S. 1008 , 103 S.Ct. 358 , 74 L.Ed.2d 394 (1982).

The cities, seizing upon broad language in Ford Motor Co., 673 F.2d at 1009-10 , argue that any agency principle of general application that changes existing law must pass through formal rulemaking procedures. Even if this were an accurate statement of the law, FERC’s clarification of its suspension policy in West Texas was a minor adjustment, a fine tuning of doctrine that does not require rulemaking unless it imposes severe hardship or circumvents existing rules. By contrast, Ford Motor Co. involved a new interpretation of the Uniform Commercial Code that would have changed long-standing creditor practices. 3

*660 C. Judicial review of preliminary dispositions in rate cases

The Federal Power Act permits review in the court of appeals for “any party ... aggrieved by an order issued by the Commission.” 16 U.S.C. § 8257 (b). Soon after the Act was enacted, the Supreme Court narrowed the literally broad scope of judicial review by excluding procedural orders from those reviewable. FPC v. Metropolitan Edison Co., 304 U.S. 375 , 58 S.Ct. 963 , 82 L.Ed. 1408 (1938). The Court has never ruled on the reviewability of suspension orders or other preliminary dispositions under the Federal Power Act, but there is a wealth of precedent under analogous provisions of the Interstate Commerce Act. 4 Arrow Transportation Co. v. Southern Railway Co., 372 U.S. 658 , 83 S.Ct. 984 , 10 L.Ed.2d 52 (1963), held that courts may not enjoin rates from taking effect after the expiration of the maximum statutory suspension period. The Court said that “Congress meant to foreclose a judicial power to interfere with the timing of rate changes.” Id. at 668 , 83 S.Ct. at 989 (emphasis in original). United States v. SCRAP, 412 U.S. 669 , 93 S.Ct. 2405 , 37 L.Ed.2d 254 (1973), reversed the district court for enjoining a rate increase the Interstate Commerce Commission had declined to suspend. “Arrow was grounded on the lack of power in the courts to grant any injunction before the Commission had finally determined the lawfulness of the rates,” wrote the Court. Id. 372 U.S. at 691 , 93 S.Ct. at 2417 . In Southern Railway Co. v. Seaboard Allied Milling Corp., 442 U.S. 444 , 99 S.Ct. 2388 , 60 L.Ed.2d 1017 (1979), the ICC’s decision not to investigate a proposed rate schedule was held not reviewable. The Court stated: “In view of this linkage [between investigation and suspension], we need look no further *661 than our previous decisions concluding that the merits of a suspension decision are not reviewable [citing United States v. SCRAP, Arrow, and Aberdeen & Rockfish R. Co. v. SCRAP, 422 U.S. 289, 311 , 95 S.Ct. 2336, 2351 , 45 L.Ed.2d 191 (1975).]” Id. at 458, 99 S.Ct. at 2396 .

Numerous federal appellate panels have declined to review FERC’s preliminary disposition of rate filings. In some cases, like the present dispute, customers have challenged one-day suspensions as too short. Borough of Ellwood City v. FERC, 701 F.2d 266 (3d Cir.1983); City of Westfield v. FPC, 551 F.2d 468 (1st Cir.1977), Municipal Light Boards v. FPC, 450 F.2d 1341 (D.C.Cir.1971). In others, customers have argued that FERC should have rejected the filing as defective on its face. Delmarva Power & Light Co. v. FERC, 671 F.2d 587 (D.C.Cir.1982); Papago Tribal Utility Authority v. FERC, 628 F.2d 235 (D.C.Cir.), cert. denied, 449 U.S. 1061 , 101 S.Ct. 784 , 66 L.Ed.2d 604 (1980); Municipal Light Boards, supra. In one recent case, the customer challenged FERC’s decision to accept a new rate schedule without a hearing. Cities of Carlisle v. FERC, 704 F.2d 1259 (D.C.Cir.1983). Utilities have attacked five-month suspensions as too long, without success. Southern California Edison Co. v. FERC, 686 F.2d 43 (D.C.Cir.1982); Delmarva Power and Light, supra.

The rationale for the unreviewability doctrine is straightforward and well-articulated. See Papago, 628 F.2d at 238-44 . Preliminary dispositions of rate cases are not final decisions on the reasonableness of proposed rates. FERC has at most 60 days to decide on suspension. To subject a rough, preliminary decision to judicial scrutiny, especially where the final rate decision is reviewable, would disrupt the administrative process unnecessarily. Further, the discretionary phrasing of 16 U.S.C. § 824d(e) argues for judicial deference, Southern Railway, 442 U.S. at 456-9 , 99 S.Ct. at 2395-96 (construing the analogous Interstate Commerce Act), as does the risk of non-uniformity wrought by uncoordinated rulings of various circuits. See Arrow, 372 U.S. at 663, 83 S.Ct. at 986 (discussing the origins of the ICC’s rate suspending powers). Finally, customers are protected by the right to a refund with interest, accrued at the prime rate and compounded quarterly. 18 C.F.R. § 35 .19a(a)(2). The cities argue that “forced loans” irreparably harm them regardless of subsequent refunds. Even if this is true, it has never been found decisive. In fact, most of the plaintiffs — e.g., the competing carriers in Arrow, the utility plaintiffs, and the customers in cases where no suspension had been ordered — were not protected by refunds, but were still denied judicial review.

The cities argue that FERC misapplied its own West Texas criteria in this case and erred by failing to make summarily certain corrections proposed by the cities and acceded to by Edison. Faced with the formidable weight of policy and precedent supporting unreviewability, the cities rely on Connecticut Light and Power v. FERC, 627 F.2d 467 (D.C.Cir.1980), the same case that stimulated the development of FERC’s suspension policy culminating in West Texas. FERC had explained its five-month suspension of Connecticut Light and Power’s rates with boilerplate language, stating only that the rates “have not been shown to be just and reasonable and may be unjust, unreasonable, unduly discriminatory, or otherwise unlawful.” Observing that identical language had been used to justify a one-month suspension in a contemporaneous case, the court said, “Indistinguishable rationales for differing results constitute no rationale at all,” and remanded. Id. at 471 .

Connecticut Light and Power carved out an exception to unreviewability that threatens to swallow the rule. In reviewing the reasons given for distinguishing between similarly situated plaintiffs, courts can dig deep into the merits of the contested rates, especially since the suspension standard refers to the ultimate reasonableness of the rates. The District of Columbia Circuit has moved to preserve the rule of unreviewability. Judge Wilkey, author of Connecticut Light and Power , wrote in Delmarva Power & Light, 671 F.2d at 595 :

We follow the D.C. Circuit and refuse to extend Connecticut Light and Power . We will not review FERC’s suspension decision under the guise of examining the adequacy of its reasons. There will be ample opportunity to correct any agency abuses after a decision on the merits of Edison’s proposed rate increase. 5

Affirmed.

. The five cities of Anaheim, Riverside, Banning, Colton, and Azusa, California have appealed together and will be referred to as “the cities.” The city of Vernon has intervened and filed a short brief.

. 16 U.S.C. § 824d(e) reads as follows:

This section was enacted as § 213 of the Federal Power Act in August, 1935, 49 Stat. 851 , and was designated as § 205 of the Federal Water Power Act.

. The cities also challenge the substance of the West Texas policy as contrary to the consumerist purposes of the Federal Power Act. But it is readily apparent that West Texas does not conflict with any provision of the Act. General propositions from the legislative history, such as those cited in the cities’ brief, are no substitute for analysis of the Federal Power Act’s *660 particular accommodation of producer and consumer interests. See FPC v. Memphis Light, 411 U.S. 458, 474 , 93 S.Ct. 1723, 1732 , 36 L.Ed.2d 426 (1973); Consumer Product Safety Commission v. GTE Syivania, Inc., 447 U.S. 102, 108 , 100 S.Ct. 2051, 2056 , 64 L.Ed.2d 766 (1980).

. Compare the former 49 U.S.C. § 15 (7), set out below, with 16 U.S.C. § 824d(e), set out at footnote two:

The current analog of this section can be found at 49 U.S.C.A. § 10708 .

. While courts are properly hesitant to invade FERC’s zone of discretion, they are free to construe the governing statutes that define the scope of FERC’s authority. In Otter Tail Power Co. v. FERC, 583 F.2d 399 (8th Cir.1978), cert. denied, 440 U.S. 950 , 99 S.Ct. 1431 , 59 L.Ed.2d 639 (1979), the court examined whether a rate filing was a “new rate” under the terms of 16 U.S.C. § 824d. The Supreme Court addressed the same issue under an analogous provision of the Interstate Commerce Act in Trans Alaska Pipeline Rate Cases, 436 U.S. 631 , 98 S.Ct. 2053 , 56 L.Ed.2d 591 (1978). In Indiana & Michigan Electric Company v. FPC, 502 F.2d 336 (D.C.Cir.1974), cert. denied, 420 U.S. 946 , 95 S.Ct. 1326 , 43 L.Ed.2d 424 (1975), the Commission had effectively lengthened the maximum five-month suspension period by impermissibly postponing the start of the suspension. The court reversed.

As we observed at footnote three, this avenue of judicial review is unavailing. West Texas does not contravene the governing statutes.