| Pay vs Performance Disclosure number in Thousands | 12 Months Ended |
| Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) |
| Pay vs Performance Disclosure [Table] | | | |
| Pay vs Performance [Table Text Block] | Year Principal Executive Officer Named Executive Officers (1) Value of Initial Fixed $100 Investment Based On: Net Income Operating Income Summary Compensation Table Compensation Paid (2) Summary Compensation Table Compensation Paid (3) Energy Recovery (4) Peer Group (5) ($) ($) ($) ($) ($) ($) ($) ($) (In thousands, except value of initial fixed investment which are presented in whole dollars) 2022 2,033 2,123 1,008 1,004 209.30 135.85 24,049 24,829 2021 2,007 4,671 859 1,736 219.51 155.20 14,269 13,831 2020 2,092 3,266 834 1,110 139.33 121.49 26,387 31,294 | | |
| Named Executive Officers, Footnote [Text Block] | Includes average CAP of all NEOs (current and previous) excluding the Company’s PEO, who was Mr. Mao for 2022, 2021 and 2020. For fiscal years 2022 and 2021, NEOs compensation comprised of Messrs. Ballard, Clemente, Ghasripoor and Yeung. For fiscal year 2020, NEOs compensation comprised of Messrs. Ballard, Clemente and Ghasripoor, and Ms. Emily Smith. | | |
| PEO Total Compensation Amount | $ 2,033,000 | $ 2,007,000 | $ 2,092,000 |
| PEO Actually Paid Compensation Amount | $ 2,123,000 | 4,671,000 | 3,266,000 |
| Adjustment To PEO Compensation, Footnote [Text Block] | In accordance with SEC rules, the following adjustments were made to determine the CAP to our PEO during fiscal years 2022, 2021 and 2020, which consist solely of adjustments to the PEO’s equity awards: Deductions Additions Year Summary Compensation Table Stock Awards Granted in the Year Fair Value of Equity Awards Granted in the Year and Unvested at Year End Year over Year Change in Fair Value of Outstanding and Unvested Equity Awards Year over Year Change in Fair Value of Equity Awards Granted in Prior Years that Vested in the Year Total Adjustments from Amounts Presented in the Summary Compensation Table * Total Compensation * ($) ($) ($) ($) ($) ($) ($) (In thousands) 2022 2,033 (1,000) 1,218 (101) (28) 89 2,123 2021 2,007 (1,001) 2,161 978 525 2,664 4,671 2020 2,092 (1,224) 2,430 — (32) 1,174 3,266 * Amounts may not total due to rounding. | | |
| Non-PEO NEO Average Total Compensation Amount | $ 1,008,000 | 859,000 | 834,000 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 1,004,000 | 1,736,000 | 1,110,000 |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | In accordance with SEC rules, the following adjustments were made to determine the CAP on average to our non-PEO NEOs during fiscal years 2022, 2021 and 2020, which consist solely of adjustments to the non-PEO NEOs’ equity awards: Deductions Additions Year Summary Compensation Table Stock Awards Granted in the Year Fair Value of Equity Awards Granted in the Year and Unvested at Year End Year over Year Change in Fair Value of Outstanding and Unvested Equity Awards Year over Year Change in Fair Value of Equity Awards Granted in Prior Years that Vested in the Year Total Adjustments from Amounts Presented in the Summary Compensation Table * Total Compensation * ($) ($) ($) ($) ($) ($) ($) (In thousands) 2022 1,008 (444) 508 (31) (37) (4) 1,004 2021 859 (331) 629 388 191 877 1,736 2020 834 (337) 450 172 (9) 276 1,110 * Amounts may not total due to rounding. | | |
| Compensation Actually Paid vs. Total Shareholder Return [Text Block] | The following graph presents the relationship between CAP to the Company’s PEO and the average of all of the Company’s NEOs, excluding the Company’s PEO (current and prior), and to the cumulative TSRs of the Company and the Peer Group. | | |
| Compensation Actually Paid vs. Net Income [Text Block] | The following graph presents the relationship between CAP to the Company’s PEO and the average of all of the Company’s NEOs, excluding the Company’s PEO (current and prior), and to the Company’s operating and net income. | | |
| Total Shareholder Return Vs Peer Group [Text Block] | The following graph presents the relationship between CAP to the Company’s PEO and the average of all of the Company’s NEOs, excluding the Company’s PEO (current and prior), and to the cumulative TSRs of the Company and the Peer Group. | | |
| Total Shareholder Return Amount | $ 209.30 | 219.51 | 139.33 |
| Peer Group Total Shareholder Return Amount | 135.85 | 155.20 | 121.49 |
| Net Income (Loss) | $ 24,049,000 | $ 14,269,000 | $ 26,387,000 |
| Company Selected Measure Amount | 24,829 | 13,831 | 31,294 |
| PEO Name | Mr. Mao | | |
| Additional 402(v) Disclosure [Text Block] | Cumulative total shareholder return of our common stock from December 31, 2019 to December 31, 2020, 2021 and 2022, respectively. Assumes the investment of $100 in our common stock on December 31, 2019 and assumes the reinvestment of dividends, if any, although dividends have never been declared on our common stockCumulative total shareholder return of our peer group used in 2022, as discussed above under “Compensation Discussion and Analysis,” from December 31, 2019 to December 31, 2020, 2021 and 2022, respectively. Assumes the investment of $100 on December 31, 2019 and assumes the reinvestment of dividends.As described in greater detail in “ Compensation Discussion and Analysis | | |
| PEO [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ 89,000 | $ 2,664,000 | $ 1,174,000 |
| PEO [Member] | Stock Awards Adjustments [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (1,000,000) | (1,001,000) | (1,224,000) |
| PEO [Member] | Equity Awards Granted During The Year, Unvested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 1,218,000 | 2,161,000 | 2,430,000 |
| PEO [Member] | Equity Awards Outstanding, Unvested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (101,000) | 978,000 | 0 |
| PEO [Member] | Equity Awards Granted In Prior Years, Vested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (28,000) | 525,000 | (32,000) |
| Non-PEO NEO [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ (4,000) | 877,000 | 276,000 |
| Non-PEO NEO [Member] | Measure [Axis]: 1 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Revenue | | |
| Non-PEO NEO [Member] | Measure [Axis]: 2 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Gross margin | | |
| Non-PEO NEO [Member] | Measure [Axis]: 3 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Operating expenses | | |
| Non-PEO NEO [Member] | Measure [Axis]: 4 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Operating income | | |
| Non-PEO NEO [Member] | Measure [Axis]: 5 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Earnings per share | | |
| Non-PEO NEO [Member] | Stock Awards Adjustments [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ (444,000) | (331,000) | (337,000) |
| Non-PEO NEO [Member] | Equity Awards Granted During The Year, Unvested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 508,000 | 629,000 | 450,000 |
| Non-PEO NEO [Member] | Equity Awards Outstanding, Unvested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (31,000) | 388,000 | 172,000 |
| Non-PEO NEO [Member] | Equity Awards Granted In Prior Years, Vested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ (37,000) | $ 191,000 | $ (9,000) |
