| Value | Category | Cases | |
|---|---|---|---|
| 1 | Central heating system | 25 |
1.3%
|
| 2 | Electric heater | 1 |
0.1%
|
| 3 | Boiler | 18 |
0.9%
|
| 4 | Stove | 1938 |
96.9%
|
| Sysmiss | 18 |
0.9%
|