| 2000 | 2018 | 2019 | 2020 | 2021 | ||
|---|---|---|---|---|---|---|
| Total Apartments Heating System Stock (thousands) | 1426.5 | 1796.2 | 1825.4 | 1856.8 | 1890.3 | |
Heating System Stock by Heating System Type (thousands) | ||||||
| Heating Oil – Normal Efficiency | 68.2 | 0.0 | 0.0 | 0.0 | 0.0 | |
| Heating Oil – Medium Efficiency | 149.6 | 121.6 | 109.0 | 94.8 | 80.0 | |
| Heating Oil – High Efficiency | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | |
| Natural Gas – Normal Efficiency | 60.3 | 0.0 | 0.0 | 0.0 | 0.0 | |
| Natural Gas – Medium Efficiency | 7.3 | 8.4 | 8.0 | 7.8 | 7.6 | |
| Natural Gas – High Efficiency | 10.1 | 85.7 | 88.2 | 90.9 | 93.6 | |
| Electric | 971.9 | 1430.8 | 1468.1 | 1508.5 | 1551.5 | |
| Heat Pump | 8.4 | 16.6 | 17.3 | 18.1 | 18.9 | |
| Other1 | 1.9 | 7.1 | 7.6 | 8.1 | 8.6 | |
| Wood | 94.2 | 47.8 | 47.0 | 46.2 | 45.4 | |
Dual Systems | ||||||
| Wood/Electric | 16.2 | 20.3 | 20.7 | 21.2 | 21.6 | |
| Wood/Heating Oil | 6.6 | 8.3 | 8.5 | 8.6 | 8.8 | |
| Natural Gas/Electric | 6.4 | 10.0 | 10.3 | 10.6 | 10.9 | |
| Heating Oil/Electric | 25.4 | 39.6 | 40.8 | 42.0 | 43.2 | |
Shares (%) | ||||||
| Heating Oil – Normal Efficiency | 4.8 | 0.0 | 0.0 | 0.0 | 0.0 | |
| Heating Oil – Medium Efficiency | 10.5 | 6.8 | 6.0 | 5.1 | 4.2 | |
| Heating Oil – High Efficiency | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | |
| Natural Gas – Normal Efficiency | 4.2 | 0.0 | 0.0 | 0.0 | 0.0 | |
| Natural Gas – Medium Efficiency | 0.5 | 0.5 | 0.4 | 0.4 | 0.4 | |
| Natural Gas – High Efficiency | 0.7 | 4.8 | 4.8 | 4.9 | 5.0 | |
| Electric | 68.1 | 79.7 | 80.4 | 81.2 | 82.1 | |
| Heat Pump | 0.6 | 0.9 | 0.9 | 1.0 | 1.0 | |
| Other1 | 0.1 | 0.4 | 0.4 | 0.4 | 0.5 | |
| Wood | 6.6 | 2.7 | 2.6 | 2.5 | 2.4 | |
Dual Systems | ||||||
| Wood/Electric | 1.1 | 1.1 | 1.1 | 1.1 | 1.1 | |
| Wood/Heating Oil | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | |
| Natural Gas/Electric | 0.4 | 0.6 | 0.6 | 0.6 | 0.6 | |
| Heating Oil/Electric | 1.8 | 2.2 | 2.2 | 2.3 | 2.3 | |