| 1990 | 2015 | 2016 | 2017 | ||
|---|---|---|---|---|---|
| Total Apartments Heating System Stock (thousands) | 369.1 | 680.3 | 693.5 | 726.8 | |
Heating System Stock by Heating System Type (thousands) | |||||
| Heating Oil – Normal Efficiency | 43.6 | 0.5 | 0.1 | 0.0 | |
| Heating Oil – Medium Efficiency | 0.6 | 23.7 | 24.6 | 26.5 | |
| Heating Oil – High Efficiency | 0.0 | 0.0 | 0.0 | 0.0 | |
| Natural Gas – Normal Efficiency | 176.1 | 7.5 | 2.7 | 0.0 | |
| Natural Gas – Medium Efficiency | 8.5 | 156.7 | 150.8 | 143.3 | |
| Natural Gas – High Efficiency | 17.4 | 210.5 | 228.2 | 256.9 | |
| Electric | 96.3 | 230.3 | 234.6 | 245.0 | |
| Heat Pump | 2.9 | 12.6 | 13.2 | 14.1 | |
| Other1 | 3.7 | 10.8 | 11.0 | 11.5 | |
| Wood | 18.1 | 23.8 | 24.2 | 25.4 | |
Dual Systems | |||||
| Wood/Electric | 1.6 | 2.6 | 2.7 | 2.7 | |
| Wood/Heating Oil | 0.2 | 0.3 | 0.3 | 0.3 | |
| Natural Gas/Electric | 0.0 | 1.1 | 1.2 | 1.2 | |
| Heating Oil/Electric | 0.0 | 0.0 | 0.0 | 0.0 | |
Shares (%) | |||||
| Heating Oil – Normal Efficiency | 11.8 | 0.1 | 0.0 | 0.0 | |
| Heating Oil – Medium Efficiency | 0.2 | 3.5 | 3.5 | 3.6 | |
| Heating Oil – High Efficiency | 0.0 | 0.0 | 0.0 | 0.0 | |
| Natural Gas – Normal Efficiency | 47.7 | 1.1 | 0.4 | 0.0 | |
| Natural Gas – Medium Efficiency | 2.3 | 23.0 | 21.7 | 19.7 | |
| Natural Gas – High Efficiency | 4.7 | 30.9 | 32.9 | 35.3 | |
| Electric | 26.1 | 33.8 | 33.8 | 33.7 | |
| Heat Pump | 0.8 | 1.9 | 1.9 | 1.9 | |
| Other1 | 1.0 | 1.6 | 1.6 | 1.6 | |
| Wood | 4.9 | 3.5 | 3.5 | 3.5 | |
Dual Systems | |||||
| Wood/Electric | 0.4 | 0.4 | 0.4 | 0.4 | |
| Wood/Heating Oil | 0.1 | 0.0 | 0.0 | 0.0 | |
| Natural Gas/Electric | 0.0 | 0.2 | 0.2 | 0.2 | |
| Heating Oil/Electric | 0.0 | 0.0 | 0.0 | 0.0 | |