Table of Contents required in evaluating discount rates, performing audit procedures to evaluate whether the expected return rates, replacement costs and discount rate were appropriately determined as of December 31, 2023, required a high degree of auditor judgment and an increased extent of effort. How the Critical Audit Matter Was Addressed in the Audit Our audit procedures related to the estimated warranty return rates, estimated replacement costs and discount rate used in determining the warranty obligation included the following, among others: – We tested the effectiveness of controls utilized in the review of the warranty obligation calculation, including controls over the determination of estimated warranty return rates, estimated replacement costs and discount rate. – We evaluated the methods and assumptions used by management to estimate warranty return rates, estimated replacement costs and discount rate used as part of the calculation of the warranty obligation by: • Testing the underlying data that served as the basis for the Company’s return rates analysis, which include historical warranty returns and historical product sales, in order to evaluate the various assumptions and historical data consisting of failure of individual components contained in its microinverters and storage products. • Comparing management’s prior-year assumptions of expected return rates to actual warranty returns received during the current year to identify potential bias in the determination of the return rates estimates used in the warranty obligation recorded. • Testing the relevant inputs into the Company’s per unit replacement costs, including third party vendor quotes. • Testing the discount rate used in the Company’s warranty obligation, utilizing internal fair value specialists. /s/ DELOITTE & TOUCHE LLP San Francisco, California February 9, 2024 We have served as the Company’s auditor since 2010. Enphase Energy, Inc. | 2023 Form 10-K | 66