| Document and Entity Information | Jul. 25, 2022 |
| Document And Entity Information [Line Items] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001794621 |
| Document Type | 8-K |
| Document Period End Date | Jul. 25, 2022 |
| Entity Registrant Name | QUANERGY SYSTEMS, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-39222 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Common Stock 0.0001 Par Value Per Share 2 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 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 11.50 Per Share 1 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Warrants, each whole warrant exercisable for one share of Common Stock at an exercise price of $11.50 per share |
| Trading Symbol | QNGY WS |
| Security Exchange Name | NYSE |
