tion." Congress by these terms plainly was trying to reconcile the claims of federal and of local authorities and to apportion federal and state jurisdiction over the industry. To define the scope of state controls, Congress employed terms of limitation perhaps less scientific, less precise, less definite than the terms of the grant of federal power. The expression "facilities used in local distribution" is one of relative generality. But as used in this Act it is not a meaningless generality in the light of our history and the structure of our government. We hold the phrase to be a limitation on jurisdiction and a legal standard that must be given effect in this case in addition to the technological transmission test. Nor do we think the exemption of "facilities used in local distribution" exempts only those which do not carry any trace of out-of-state energy. Congress has said without qualification that the Commission shall not, unless specifically authorized elsewhere in the Act, have jurisdiction "over facilities used in local distribution." To construe this as meaning that, even if local, facilities come under jurisdiction of the Federal Commission because power from out of state, however trifling, comes into the system, would nullify the exemption and as a practical matter would transfer to federal jurisdiction the regulation of many local companies that we think Congress intended to leave in state control. It does not seem important whether out-of-state energy gets into local distribution facilities. They may carry no energy except extra-state energy and still be exempt under the Act. The test is whether they are local distribution facilities. There is no specific provision for federal jurisdiction over accounting except as to "public utilities." The order must stand or fall on whether this company owned facilities that were used in transmission of interstate power and which were not facilities used in local distribution. Opinion of the Court. 324 U.S. Since the Court of Appeals considered irrelevant the jurisdictional test which we find to be imposed by Congress, the inquiry on review has not proceeded under a correct rule of law and it follows that the judgment of the Court of Appeals must be reversed. Whether the Commission's decision was reached under the same misapprehension of the law of its jurisdiction is not made so clear from its findings or opinion. Of course under the Act "The finding of the Commission as to the facts, if supported by substantial evidence, shall be conclusive." § 313 (b). The Commission has found that each of the facilities in question is "used for the transmission of electric energy purchased as aforesaid from the Connecticut Power Company, as distinguished from local distribution thereof." It has not, however, made an explicit finding that these facilities are not used in local distribution; and we are in doubt whether by application of the statute as herein construed it could have done so. We have said, and it is applicable to this case, that "Where a federal agency is authorized to invoke an overriding federal power except in certain prescribed situations and then to leave the problem to traditional state control, the existence of federal authority to act should appear affirmatively and not rest on inference alone." Yonkers v. United States, 320 U. S. 685, 692; Florida v. United States, 282 U. S. 194, 211-12; cf. Palmer v. Massachusetts, 308 U. S. 79, 84; Federal Trade Commission v. Bunte Bros., 312 U. S. 349, 351. Nothing except explicit findings excluding the grounds of state control gives assurance that the bounds of federal jurisdiction have been accurately understood and fully respected, and that state power has been considerately and deliberately overlapped. The findings and opinion of the Commission leave us in doubt, to say the least, as to whether what we consider limitations on the jurisdiction of the Commission were so considered by it. The only specific reference to the sub ject is the statement that "Respondent's contentions that it is subject to regulation by the Public Utilities Commission of the State of Connecticut and therefore not subject to the regulation provided by the Federal Power Act must be rejected," citing Northwestern Electric Co. v. Federal Power Commission, 125 F. 2d 882, and In the Matter of Hartford Electric Light Co., 2 F. P. C. 502, aff'd, 131 F.2d 953. In both of those cases factual differences in reference to the status of the company as a public utility were involved, and we agree with the Commission that once a company is properly found to be a "public utility" under the Act the fact that a local commission may also have regulatory power does not preclude exercise of the Commission's functions. Cf. Northwestern Electric Co. v. Federal Power Commission, 321 U. S. 119. But such a rejection of state control as grounds of exemption must be preceded by the finding, giving due weight to the policy declaration in doubtful cases, that the company in question is a "public utility" by reason of ownership of facilities not used in local distribution. In determining this the Commission announced and applied a rule which appears to be one of law as to interstate transmission: "Such transmission, in our opinion, extends from the generator, where generation is complete [citing Utah Power & Light Co. v. Pfost, 286 U. S. 165, 181] to the point where the function of conveyance in bulk over a distance, which is the essential characteristic of 'transmission,' is completed and the process of subdividing the energy to serve ultimate consumers, which is the characteristic of 'local distribution,' is begun [citing Southern Gas Corp. v. Alabama, 301 U. S. 148, 155; and East Ohio Gas Co. v. Tax Commission, 283 U. S. 465, 471]." The Southern and East Ohio cases both involved natural gas transportation into a state and sales of gas at retail therein. Each was a tax case in which the state 637582°-46- -38 Opinion of the Court. 324 U.S. asserted that the sales within the state constituted an intrastate business which in one case would support a state levy of an annual franchise tax based on the actual amount of capital employed in the state; and in the other, an excise tax based on gross receipts from the business within the state. The companies each contended that sales made to consumers within the state were still within interstate commerce and hence there was no state jurisdiction to tax. In neither case was this Court required to determine the exact point at which interstate commerce ceased and intrastate commenced. It was required to find only some "doing of business" within the state in order to sustain the constitutionality of the statutes involved. In both cases it upheld the power of the state to tax and in both held that the distribution at low pressure was a local business for taxation purposes as distinguished from transmission in interstate commerce. But a holding that distributing gas at low pressure to consumers is a local business is not a holding that the process of reducing it from high to low pressure is not also part of such local business. In so far as the Commission found in these cases a rule of law which excluded from the business of local distribution the process of reducing energy from high to low voltage in subdividing it to serve ultimate consumers, the Commission has misread the decisions of this Court. No such rule of law has been laid down. But for such an erroneous view of the law established by our decisions it seems doubtful if the Commission would have reached the conclusion that it did upon this record. Nor is it clear that if it were reached it would be supported by substantial evidence. Expert testimony received by the Commission on the subject from the Commission's own experts seems to have been predicated upon the Commission's understanding of the law. It is not for us to make an original appraisal of the facts. We do not therefore undertake to decide as an original matter whether the facilities in question are or are not facilities which can subject the Company to the Act. Nor do we undertake to pass upon the contention of the Government that even if the present facilities do not constitute a sufficient basis for federal jurisdiction the operation of other facilities since abandoned subjects the Company to the accounting order of the Commission for the period of January 1, 1937, when it became effective, until June 1, 1941 or some other date, depending on the facility found to be the basis of jurisdiction. The Company contends that to make it install an expensive system of accounting for a period that was short and has already expired would be a mere waste of time and money and would be of no practical benefit. The Commission contends that the accounting requirements and information would tend to discourage further write-ups and inflation of accounts and would amount to "regulation by the informatory process." It contends that this company has been guilty of accounting abuses in the nature of write-ups and the creation of fictitious surpluses which would be eliminated or at least discouraged by an application of its uniform system of accounts. The Company denies that such abuses exist. It is not, however, contended that Congress has conferred any jurisdiction upon the Commission to reach accounting abuses when and if they exist except as to companies which own facilities subject to the jurisdiction of the Commission. In other companies the correction of these abuses, if they exist, is left to the state government, which has this company completely within its power and whose constituents are the sufferers by any abuses that may exist. We will not undertake to make an original finding as to jurisdiction for a period, any more than as to jurisdiction at the present time. Another contention made by the Company may be shortly disposed of. It is contended that the volume of energy passing over certain of these facilities is insignifi |