| Region |
| Bias | REQM | Average Global Irradiation Measured | ||
| r | Wh/m2 | % | Wh/m2 | % | Wh/m2 | |
| North | 0.81 | 30 | 0.6 | 467 | 9.7 | 4825 |
| Northeast | 0.87 | 12 | 0.2 | 456 | 8.3 | 5483 |
| Midwest | 0.86 | 23 | 0.5 | 421 | 8.3 | 5082 |
| Southwest | 0.91 | 4 | 0.1 | 416 | 8.4 | 4951 |
| South | 0.98 | -4 | 0.1 | 395 | 8.9 | 4444 |
| Average | 0.89 | 12 | 0.2 | 421 | 8.3 | 5153 |