Exhibit 99.1

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

Lightning eMotors, Inc. (f/k/a GigCapital3, Inc.) (the “Company”) is providing the following unaudited pro forma condensed combined financial information to aid you in your analysis of the financial aspects of the business combination between GigCapital3, Inc. and Lightning Systems, Inc., which was consummated on May 6, 2021. The historical financial information of Lightning Systems, Inc. was derived from the audited financial statements of Lightning Systems, Inc. as of and for the twelve months ended December 31, 2020. The historical financial information of GigCapital3, Inc. was derived from the audited financial statements of GigCapital3, Inc. for the period from inception (February 3, 2020) through December 31, 2020. This information should be read together with Lightning Systems, Inc.’s and GigCapital3 Inc.’s financial statements and related notes.

Description of the Transaction

On December 10, 2020, GigCapital3, Inc. and its wholly owned subsidiary, Project Power Merger Sub, Inc., entered into a Business Combination Agreement with Lightning Systems, Inc. Following the approval at the special meeting of the stockholders of GigCapital3, Inc. held on April 21, 2021, and pursuant to and in accordance with the terms of the Business Combination Agreement, Project Power Merger Sub, Inc. merged with and into Lightning Systems, Inc. with Lightning Systems Inc. surviving the merger. Upon the consummation of the merger, GigCapital3, Inc. changed its name to Lightning eMotors, Inc.

Subject to and in accordance with the terms of the Business Combination Agreement and customary adjustments, at the effective time of the merger, each share of Lightning Systems, Inc. capital stock issued and outstanding immediately prior to the effective time of the merger (other than shares owned by Lightning Systems, Inc. as treasury stock or dissenting shares) (i) converted into that number of shares of GigCaptial3, Inc. common stock that constitutes the merger consideration, which aggregate amount, including any shares issuable in respect of vested equity awards of Lightning Systems, Inc. that were exercised prior to the closing or equity awards of Lightning Systems, Inc. that GigCapital3, Inc. assumed and which are exercised following the closing in accordance with the terms of such equity awards, plus (2) up to an additional 16,463,096 shares of GigCapital3, Inc. common stock as stockholder earnout shares to former equity holders of Lightning Systems, Inc. who have received, or are entitled to receive, any per share merger consideration shares of GigCapital3, Inc. common stock earned due to the satisfaction of the earnout conditions set forth in and pursuant to the terms of the Business Combination Agreement.

Accounting for the Transactions

The business combination is accounted for as a reverse recapitalization in accordance with U.S. GAAP. Under this method of accounting, GigCapital3, Inc. will be treated as the “acquired” company for financial reporting purposes. This determination was primarily based on Lightning System, Inc.’s operations comprising substantially all of the ongoing operations of the post-combination company, Lightning System, Inc.’s senior management comprising substantially all of the senior management of the post-combination company and the existence of a majority voting interest in the post-combination company. Accordingly, for accounting

purposes, the business combination is treated as the equivalent of Lightning System, Inc. issuing stock for the net assets of GigCapital3, Inc., accompanied by a recapitalization. The net assets of GigCapital3, Inc. is stated at historical cost, with no goodwill or other intangible assets recorded. Operations prior to the business combination are the historical operations of Lightning System, Inc.

Basis of Pro Forma Presentation

The historical financial information has been adjusted to give pro forma effect to events that are related and/or directly attributable to the business combination, are factually supportable and, with respect to the pro forma statements of operations, are expected to have a continuing impact on the results of the post-combination company. The unaudited pro forma condensed combined financial information is for illustrative purposes only. The financial results may have been different had the companies always been combined. You should not rely on the unaudited pro forma condensed combined financial information as being indicative of the historical results that would have been achieved had the companies always been combined or the future results that the post-combination company will experience. Lightning System, Inc. and GigCapital3, Inc. have not had any historical relationship prior to the business combination. Accordingly, no pro forma adjustments were required to eliminate activities between the companies.

PRO FORMA CONDENSED COMBINED BALANCE SHEET AS OF DECEMBER 31, 2020

(in thousands except share and per share amounts)

(unaudited)

Pro Forma Adjustments to the Unaudited Condensed Combined Balance Sheet

(A) Derived from the audited condensed balance sheet of the Gig Capital 3, Inc. as of December 31, 2020.

(B) Derived from the audited condensed consolidated balance sheet of Lightning Systems as of December 31, 2020.

(1) To reflect the release of $202,029,000 of investments and $2,000 of interest receivable held in the Trust Account as all amounts held in the Trust Account are to be released upon the consummation of the Business Combination to either be used to satisfy the exercise of redemption rights or for use by New Lightning eMotors.

(2) To reflect the sale under a subscription agreement with PIPE Investor of 2,500,000 shares at $10.00 per share for a total of $25.0 million.

(3) To reflect the issuance of Convertible Notes due in 2024 to Convertible Note Investors totaling $100 million, the derivative liability for the conversion feature, mandatory redemption and the interest make-whole provision ($42.5 million) and to reflect the debt discount resulting from the issuance of 8,695,652 warrants with the associated debt discount ($29.0 million). The Convertible Notes are convertible into Common Stock at a rate of 86.9565 shares per $1,000 of principal amount.

(4) To reflect the 5,816,664 shares redeemed into cash by the stockholders of GigCapital3, Inc. in conjunction with the vote to approve the Business Combination. To reflect the surrender of shares of Lightning Systems Capital Stock (including shares resulting from the conversion of notes, warrants and preferred stock), after redemption of the 5,816,664 shares of Common Stock, and the issuance of 50,652,890 shares of Common Stock ($0.0001 par value).

(5) To reflect the elimination of the historical accumulated deficit of GigCapital3, Inc., the accounting acquiree.

(6) To reflect the payment of estimated transaction costs of approximately $40.0 million, including debt issuance costs of $5.0 million, and deferred underwriters’ fees already accrued of $8.0 million, in conjunction with the Business Combination.

(7) To reflect the payoff of certain outstanding debt (the unsecured facility agreement and working capital facilities) of Lightning Systems, in conjunction with the closing of the Business Combination.

(8) To reflect the write off by Lightning Systems of the unamortized debt discount.

(9) To reclass the private placement warrants of GigCapital3, Inc. from equity to long-term liabilities at fair value

PRO FORMA CONDENSED COMBINED STATEMENTS OF OPERATIONS

FOR THE YEAR ENDED DECEMBER 31, 2020

(in thousands except share and per share amounts)

(unaudited)

Pro Forma Adjustments to the Unaudited Condensed Combined Statement of Operations

(A) Derived from the audited statement of operations of the GigCapital3, Inc. for the period from inception (February 3, 2020) through December 31, 2020.

(B) Derived from the audited statement of operations of Lightning Systems for the year ended December 31, 2020.

(1) Represents an adjustment to eliminate both the interest income on marketable securities held in the Trust Account as of the beginning of the period and the corresponding income tax expense.

(2) To reflect the reversal of the loss from change in fair value of warrants liabilities incurred by Lightning Systems as the Business Combination is reflected as if it had occured at the beginning of the twelve-month period.

(3) To reflect the amortization of the regular interest plus the debt discount of $71.4 million on the notes financing ($42.5 million from the derivative liability and $28.9 million resulting from the warrants issued) over three years (the term of the loan) at a constant interest rate as if the loan had occurred at the beginning of the twelve-month period.

(4) To reflect the reversal of interest (including the amorization of debt discounts) on the unsecured facility agreement and other notes that would be either converted to common stock or paid off at the start of the twelve-month period as the Business Combination is reflected as if it had occured at the beginning of the twelve-month period.

(5) To expense advisory fees paid at deal consummation as if the Business Combination had occurred at the beginning of the twelve-month period.

(6) As the Business Combination is being reflected as if it had occurred at the beginning of the twelve-month period ended December 31, 2020, the calculation of weighted average shares outstanding for basic and diluted net loss per share assumes that the shares issuable to the Lightning Systems equity holders in the Business Combination have been outstanding for the entire period presented. This calculation has been adjusted to exclude shares redeemed prior to the Business Combination.

(7) To record change in fair value of GigCapital3, Inc. private warrants due to reclassification from equity to labilities at inception to year-end as the Business Combination is reflected as if it had occurred at the beginning of the twelve-month period.

(8) To record the first year of amortization of the debt issuance costs related to the $100 million Convertible Notes as the Business Combination is reflected as if it had occurred at the beginning of the twelve-month period.

PRO FORMA CHANGE IN EQUITY ACCOUNTS

(in thousands except share and per share amounts)

(unaudited)