Primarily used for heating homes, schools, industrial premises, stables etc, but can also be used for process heat.
Standard boiler sizes (in kW): 250, 400, 600, 800, 1,000, 1,500, 2,000, 2,500, 3,000, 4,000 and 5,000.
| kW | BTU/hour |
| 250 | 853,036 |
| 400 | 1,364,857 |
| 600 | 2,047,285 |
| 800 | 2,729,714 |
| 1000 | 3,412,142 |
| 1500 | 5,118,213 |
| 2000 | 6,824,284 |
| 2500 | 8,530,355 |
| 3000 | 10,236,426 |
| 4000 | 13,648,568 |
| 5000 | 17,060,710 |