Counties Number of counties that fall within this grid evaluation area. | Grade Solar suitability grade from A+ (exceptional sunlight, roof conditions, and opportunity) to D (poor). Derived from aggregate Project Sunroof data. | Bldgs. Buildings whose rooftops are suitable for solar panels based on shade, orientation, and roof area. | % Covered Share of buildings in this region that Project Sunroof has imagery and analysis for. | % Qualified Of the buildings analyzed, the share whose rooftops are viable for solar. | kWh Total annual electricity all qualified rooftops in this region could generate combined. | Total Panels Total number of solar panels that could fit across all qualified rooftops. | CO₂ Offset Metric tons of CO₂ avoided per year if every qualified rooftop went solar. | Median Panels Typical number of panels that fit on a qualified rooftop in this region. | kW Total Combined nameplate capacity if all qualified rooftops were fully outfitted. | kW Median Typical system size for a single qualified building in this region. | Installed Solar systems already installed and operating in this region. | Adoption Share of qualified rooftops that already have a solar installation. | Untapped Bldgs. Qualified buildings in this region without any existing installation. | % Untapped Share of qualified rooftops that have not yet gone solar. | Untapped kWh/yr Annual electricity left on the table if untapped rooftops stay unbuilt. | Untapped CO₂ Metric tons of CO₂ that would be avoided per year if untapped rooftops were built. | Potential/yr Combined dollar value of energy + carbon if every untapped rooftop went solar — per year. Residential rates as of May 2026 (EIA Form 826). Actual rates vary by utility and tariff. | Potential/life 25-year lifetime value of fully developing every untapped rooftop in this region. Residential rates as of May 2026 (EIA Form 826). Actual rates vary by utility and tariff. | Untapped Cost Estimated upfront cost to install solar on every currently untapped rooftop. | Median kWh/roof Annual kWh a typical qualified roof in this region would produce. | Median Savings/yr Typical first-year electric-bill savings for a homeowner in this region going solar. Residential rates as of May 2026 (EIA Form 826). Actual rates vary by utility and tariff. | Median Life Savings 25-year electric-bill savings for the typical solar homeowner in this region. Residential rates as of May 2026 (EIA Form 826). Actual rates vary by utility and tariff. | Median Cost Typical upfront install cost for a single home in this region. | Median Payback Years until the typical homeowner recoups their install cost through bill savings. Residential rates as of May 2026 (EIA Form 826). Actual rates vary by utility and tariff. | Cars Off Road Number of gas-powered cars taken off the road equivalent to this region’s untapped solar. | Homes Powered Number of average US homes that could be fully powered by this region’s untapped solar. | |
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| PJM East | 175 | C | 7.8M | 47% | 80% | 166.7B | 576.2M | 118.8Mt | 36 | 144.1M | 9.07 | 28,155 | 0.4% | 7.8M | 99% | 166.1B | 118.4Mt | $28.9B | $723.7B | $430.6B | — | — | — | — | — | 25.8M | 15.9M |
| SERTP | 200 | B | 6.0M | 43% | 79% | 173.7B | 546.9M | 109.7Mt | 47 | 136.7M | 11.68 | 8,754 | 0.1% | 6.0M | 99% | 173.4B | 109.5Mt | $27.9B | $696.5B | $409.6B | — | — | — | — | — | 23.8M | 16.5M |
| CAISO | 42 | A | 8.6M | 69% | 87% | 243.3B | 654.8M | 67.1Mt | 50 | 163.7M | 12.61 | 331.8K | 3.8% | 8.3M | 96% | 233.9B | 64.5Mt | $22.1B | $552.8B | $472.2B | — | — | — | — | — | 14.6M | 23.2M |
| FRCC | 36 | B | 4.6M | 68% | 90% | 152.5B | 446.4M | 81.5Mt | 65 | 111.6M | 16.24 | 104.5K | 2.3% | 4.5M | 98% | 149.0B | 79.6Mt | $21.8B | $545.9B | $327.3B | — | — | — | — | — | 17.7M | 14.5M |
| MISO Central | 85 | C | 4.1M | 48% | 79% | 96.0B | 333.0M | 77.9Mt | 41 | 83.3M | 10.21 | 5,595 | 0.1% | 4.1M | 99% | 95.9B | 77.8Mt | $18.4B | $460.4B | $249.4B | — | — | — | — | — | 16.9M | 9.1M |
| ERCOT | 50 | B | 4.8M | 51% | 88% | 140.0B | 424.3M | 68.4Mt | 52 | 106.1M | 13.12 | 11,478 | 0.2% | 4.8M | 99% | 139.7B | 68.3Mt | $17.9B | $447.9B | $317.5B | — | — | — | — | — | 14.9M | 13.3M |
| SPP South | 53 | B | 1.9M | 49% | 83% | 55.2B | 167.4M | 38.3Mt | 47 | 41.8M | 11.83 | 2,842 | 0.1% | 1.9M | 99% | 55.1B | 38.3Mt | $9.1B | $227.9B | $125.4B | — | — | — | — | — | 8.3M | 5.3M |
| WestConnect South | 18 | A+ | 2.3M | 54% | 89% | 76.9B | 190.4M | 33.0Mt | 53 | 47.6M | 13.14 | 45,636 | 2.0% | 2.2M | 98% | 75.4B | 32.3Mt | $9.0B | $225.2B | $139.9B | — | — | — | — | — | 7.2M | 7.3M |
| MISO North | 63 | C | 2.1M | 54% | 77% | 52.6B | 183.5M | 33.2Mt | 40 | 45.9M | 10.01 | 3,698 | 0.2% | 2.1M | 99% | 52.5B | 33.2Mt | $8.3B | $207.6B | $137.4B | — | — | — | — | — | 7.2M | 5.0M |
| PJM West | 17 | C | 1.8M | 50% | 78% | 40.5B | 141.6M | 33.5Mt | 38 | 35.4M | 9.57 | 2,121 | 0.1% | 1.8M | 99% | 40.5B | 33.4Mt | $7.8B | $195.3B | $106.1B | — | — | — | — | — | 7.3M | 3.9M |
| NYISO | 34 | D | 2.5M | 57% | 77% | 45.1B | 158.7M | 21.9Mt | 32 | 39.7M | 7.93 | 18,784 | 0.7% | 2.5M | 99% | 44.7B | 21.8Mt | $6.2B | $153.8B | $118.2B | — | — | — | — | — | 4.8M | 4.3M |
| ISONE | 35 | C | 2.0M | 52% | 73% | 41.0B | 144.4M | 17.7Mt | 29 | 36.1M | 7.21 | 21,759 | 1.1% | 2.0M | 99% | 40.5B | 17.6Mt | $4.9B | $123.4B | $107.1B | — | — | — | — | — | 3.9M | 3.9M |
| WestConnect North | 19 | A | 1.1M | 62% | 80% | 26.6B | 75.1M | 15.8Mt | 37 | 18.8M | 9.17 | 24,383 | 2.2% | 1.1M | 98% | 26.0B | 15.4Mt | $3.8B | $94.5B | $55.1B | — | — | — | — | — | 3.4M | 2.5M |
| MISO South | 34 | B | 841.3K | 53% | 82% | 24.2B | 76.1M | 14.6Mt | 51 | 19.0M | 12.74 | 755 | 0.1% | 840.5K | 99% | 24.1B | 14.6Mt | $3.8B | $94.3B | $57.0B | — | — | — | — | — | 3.2M | 2.3M |
| NorthernGrid West | 37 | D | 2.3M | 50% | 84% | 44.0B | 169.5M | 11.7Mt | 54 | 42.4M | 13.38 | 14,408 | 0.6% | 2.3M | 99% | 43.7B | 11.6Mt | $3.4B | $85.7B | $126.4B | — | — | — | — | — | 2.5M | 4.2M |
| NorthernGrid South | 17 | A | 1.1M | 43% | 81% | 31.9B | 86.2M | 10.5Mt | 43 | 21.6M | 10.74 | 15,855 | 1.4% | 1.1M | 99% | 31.5B | 10.3Mt | $3.1B | $78.0B | $63.8B | — | — | — | — | — | 2.3M | 3.0M |
| SPP North | 9 | C | 361.1K | 64% | 85% | 8.9B | 28.8M | 4.5Mt | 43 | 7.2M | 10.69 | 231 | 0.1% | 360.9K | 99% | 8.9B | 4.5Mt | $1.1B | $28.2B | $21.6B | — | — | — | — | — | 975.6K | 843.5K |
| NorthernGrid East | 16 | B | 430.9K | 55% | 75% | 10.2B | 32.3M | 2.7Mt | 38 | 8.1M | 9.58 | 791 | 0.2% | 430.1K | 99% | 10.2B | 2.7Mt | $840.4M | $21.0B | $24.2B | — | — | — | — | — | 592.4K | 976.0K |