Description of business and summary of significant accounting policies - Revenue by Product Line and Services (Details) - USD ($) |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
Jun. 30, 2016 |
Jun. 30, 2015 |
Mar. 31, 2015 |
Jun. 30, 2016 |
Jun. 30, 2015 |
|
| Revenue by Producks and Services [Line Items] | |||||
| Products | $ 2,408,860 | $ 3,345,571 | $ 3,345,571 | $ 4,675,008 | $ 6,883,446 |
| Services | 3,278,448 | 3,038,260 | 3,038,260 | 6,087,815 | 5,603,819 |
| Total revenues | 5,687,308 | 6,383,831 | $ 6,383,831 | 10,762,823 | 12,487,265 |
| Cogeneration | |||||
| Revenue by Producks and Services [Line Items] | |||||
| Products | 1,270,499 | 2,526,812 | 2,688,471 | 5,098,740 | |
| Chiller & Heat Pump | |||||
| Revenue by Producks and Services [Line Items] | |||||
| Products | 1,138,361 | 818,759 | 1,986,537 | 1,784,706 | |
| Service Contracts | |||||
| Revenue by Producks and Services [Line Items] | |||||
| Services | 2,082,644 | 2,035,041 | 4,270,966 | 3,907,407 | |
| Installations | |||||
| Revenue by Producks and Services [Line Items] | |||||
| Services | $ 1,195,804 | $ 1,003,219 | $ 1,816,849 | $ 1,696,412 | |