| Document And Entity Information | Nov. 14, 2022 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 14, 2022 |
| Entity Registrant Name | Quanergy Systems, Inc. |
| Entity Central Index Key | 0001794621 |
| Entity Emerging Growth Company | true |
| Securities Act File Number | 001-39222 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 88-0535845 |
| Entity Address, Address Line One | 433 LAKESIDE DRIVE |
| Entity Address, City or Town | SUNNYVALE |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94085 |
| City Area Code | 408 |
| Local Phone Number | 245-9500 |
| Entity Information, Former Legal or Registered Name | Not Applicable |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Ex Transition Period | false |
| Common Stock 0.0001 Par Value Per Share 2 [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock, $0.0001 par value per share |
| Trading Symbol | QNGY |
| Security Exchange Name | NYSE |
| Warrants Each Whole Warrant Exercisable for One Share of Common Stock at an Exercise Price of 230.00 Per Share [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Warrants, each whole warrant exercisable for one share of Common Stock at an exercise price of $230.00 per share |
| Trading Symbol | QNGY WS |
| Security Exchange Name | NYSE |
