| 1990 | 2015 | 2016 | 2017 | ||
|---|---|---|---|---|---|
| Total Single Detached Heating System Stock (thousands) | 745.6 | 984.2 | 989.8 | 1,006.9 | |
Heating System Stock by Heating System Type (thousands) | |||||
| Heating Oil – Normal Efficiency | 75.0 | 0.0 | 0.0 | 0.0 | |
| Heating Oil – Medium Efficiency | 0.0 | 32.5 | 32.5 | 33.7 | |
| Heating Oil – High Efficiency | 0.0 | 0.0 | 0.0 | 0.0 | |
| Natural Gas – Normal Efficiency | 355.4 | 0.0 | 0.0 | 0.0 | |
| Natural Gas – Medium Efficiency | 13.0 | 227.1 | 215.6 | 203.2 | |
| Natural Gas – High Efficiency | 26.4 | 261.3 | 277.5 | 300.2 | |
| Electric | 170.3 | 271.8 | 270.2 | 272.6 | |
| Heat Pump | 12.9 | 43.2 | 44.1 | 45.7 | |
| Other1 | 7.5 | 14.4 | 14.3 | 14.5 | |
| Wood | 0.0 | 0.0 | 0.0 | 0.0 | |
Dual Systems | |||||
| Wood/Electric | 54.6 | 79.0 | 79.7 | 80.6 | |
| Wood/Heating Oil | 18.8 | 27.7 | 28.0 | 28.3 | |
| Natural Gas/Electric | 9.0 | 18.0 | 18.2 | 18.5 | |
| Heating Oil/Electric | 2.7 | 9.3 | 9.5 | 9.7 | |
Shares (%) | |||||
| Heating Oil – Normal Efficiency | 10.1 | 0.0 | 0.0 | 0.0 | |
| Heating Oil – Medium Efficiency | 0.0 | 3.3 | 3.3 | 3.3 | |
| Heating Oil – High Efficiency | 0.0 | 0.0 | 0.0 | 0.0 | |
| Natural Gas – Normal Efficiency | 47.7 | 0.0 | 0.0 | 0.0 | |
| Natural Gas – Medium Efficiency | 1.7 | 23.1 | 21.8 | 20.2 | |
| Natural Gas – High Efficiency | 3.5 | 26.5 | 28.0 | 29.8 | |
| Electric | 22.8 | 27.6 | 27.3 | 27.1 | |
| Heat Pump | 1.7 | 4.4 | 4.5 | 4.5 | |
| Other1 | 1.0 | 1.5 | 1.4 | 1.4 | |
| Wood | 0.0 | 0.0 | 0.0 | 0.0 | |
Dual Systems | |||||
| Wood/Electric | 7.3 | 8.0 | 8.1 | 8.0 | |
| Wood/Heating Oil | 2.5 | 2.8 | 2.8 | 2.8 | |
| Natural Gas/Electric | 1.2 | 1.8 | 1.8 | 1.8 | |
| Heating Oil/Electric | 0.4 | 0.9 | 1.0 | 1.0 | |