U.S. Solar Resource & ASHRAE Climatic Design Database
Meteorological and utility references compiled from the National Renewable Energy Laboratory (NREL National Solar Radiation Database & PVWatts V8 modeling methodology),ASHRAE Handbook — Fundamentals (Climatic Design Information), and the U.S. Energy Information Administration (EIA Electric Power Monthly).
50-State & Regional Solar & Climatic Reference Table
54 Representative Weather Stations (50 States + DC & Subdivided Metro Regions)| State & Metro | Zone | ☀️ Peak Sun Hours (h/day) | 📐 Ref. Tilt | ❄️ ASHRAE 99% Winter | 🔥 ASHRAE 1% Summer | ⚡ EIA Rate |
|---|---|---|---|---|---|---|
| Alabama (Birmingham) | 3A | 4.82 h/day | 30° | 22.1°F | 93.6°F | $0.154/kWh |
| Alaska (Anchorage) | 7 | 3.15 h/day | 55° | -6.7°F | 72.3°F | $0.248/kWh |
| Arizona (Phoenix) | 2B | 6.55 h/day | 30° | 40.8°F | 109.8°F | $0.141/kWh |
| Arkansas (Little Rock) | 3A | 4.75 h/day | 31° | 21.6°F | 95.7°F | $0.128/kWh |
| California (Los Angeles) | 3B | 5.62 h/day | 31° | 44.2°F | 86.2°F | $0.315/kWh |
| California (Central) (Fresno / Central Valley) | 3B | 5.78 h/day | 33° | 32°F | 101.5°F | $0.315/kWh |
| California (North) (San Francisco / Bay Area) | 3C | 5.38 h/day | 34° | 38.5°F | 78.4°F | $0.315/kWh |
| Colorado (Denver) | 5B | 5.48 h/day | 36° | 1.2°F | 92.3°F | $0.151/kWh |
| Connecticut (Hartford) | 5A | 4.31 h/day | 37° | 4.8°F | 89.2°F | $0.289/kWh |
| Delaware (Wilmington) | 4A | 4.58 h/day | 35° | 14.5°F | 90.7°F | $0.165/kWh |
| District of Columbia (Washington D.C.) | 4A | 4.62 h/day | 35° | 16.9°F | 92.8°F | $0.168/kWh |
| Florida (Central) (Orlando) | 2A | 5.37 h/day | 26° | 39.2°F | 93.9°F | $0.156/kWh |
| Florida (South) (Miami) | 1A | 5.49 h/day | 23° | 48.7°F | 91.6°F | $0.156/kWh |
| Georgia (Atlanta) | 3A | 4.88 h/day | 30° | 21.7°F | 92.5°F | $0.143/kWh |
| Hawaii (Honolulu) | 1A | 5.86 h/day | 19° | 62.1°F | 89.2°F | $0.442/kWh |
| Idaho (Boise) | 5B | 4.95 h/day | 39° | 11.5°F | 96.3°F | $0.112/kWh |
| Illinois (Chicago) | 5A | 4.22 h/day | 38° | -1.3°F | 90.1°F | $0.169/kWh |
| Indiana (Indianapolis) | 5A | 4.38 h/day | 36° | 3.4°F | 89.5°F | $0.152/kWh |
| Iowa (Des Moines) | 5A | 4.51 h/day | 37° | -6°F | 90.5°F | $0.138/kWh |
| Kansas (Wichita) | 4A | 5.12 h/day | 34° | 7.9°F | 98.2°F | $0.144/kWh |
| Kentucky (Louisville) | 4A | 4.49 h/day | 34° | 11.8°F | 91°F | $0.131/kWh |
| Louisiana (New Orleans) | 2A | 4.89 h/day | 27° | 32.7°F | 93.4°F | $0.124/kWh |
| Maine (Portland) | 6A | 4.28 h/day | 39° | -1.8°F | 85.1°F | $0.274/kWh |
| Maryland (Baltimore) | 4A | 4.6 h/day | 35° | 15.3°F | 92.1°F | $0.178/kWh |
| Massachusetts (Boston) | 5A | 4.25 h/day | 38° | 7.2°F | 88°F | $0.298/kWh |
| Michigan (Detroit) | 5A | 4.15 h/day | 38° | 4.5°F | 88.5°F | $0.187/kWh |
| Minnesota (Minneapolis / St. Paul) | 6A | 4.45 h/day | 40° | -13.2°F | 88.7°F | $0.157/kWh |
| Mississippi (Jackson) | 3A | 4.8 h/day | 29° | 24.1°F | 94.3°F | $0.139/kWh |
| Missouri (St. Louis / Kansas City) | 4A | 4.71 h/day | 35° | 6.8°F | 93.9°F | $0.134/kWh |
| Montana (Billings) | 6B | 4.88 h/day | 41° | -13.5°F | 92.8°F | $0.126/kWh |
| Nebraska (Omaha) | 5A | 4.82 h/day | 37° | -4.9°F | 92.1°F | $0.129/kWh |
| Nevada (Las Vegas) | 3B | 6.41 h/day | 33° | 32.7°F | 108.3°F | $0.162/kWh |
| New Hampshire (Manchester) | 5A | 4.22 h/day | 39° | -0.4°F | 87.8°F | $0.267/kWh |
| New Jersey (Newark / Jersey City) | 4A | 4.52 h/day | 37° | 14°F | 90.9°F | $0.198/kWh |
| New Mexico (Albuquerque) | 4B | 6.38 h/day | 32° | 18°F | 95.2°F | $0.149/kWh |
| New York (New York City) | 4A | 4.41 h/day | 37° | 15.1°F | 89.8°F | $0.245/kWh |
| New York (Upstate) (Buffalo / Rochester) | 5A | 3.92 h/day | 39° | 4.1°F | 85.5°F | $0.215/kWh |
| North Carolina (Charlotte / Raleigh) | 3A | 4.95 h/day | 32° | 20.3°F | 92.5°F | $0.138/kWh |
| North Dakota (Fargo / Bismarck) | 7 | 4.52 h/day | 42° | -21.1°F | 88.5°F | $0.121/kWh |
| Ohio (Columbus / Cleveland) | 5A | 4.25 h/day | 36° | 5.2°F | 88.7°F | $0.161/kWh |
| Oklahoma (Oklahoma City) | 3A | 5.28 h/day | 32° | 14.5°F | 98.4°F | $0.132/kWh |
| Oregon (Portland) | 4C | 4.12 h/day | 41° | 23.4°F | 88.9°F | $0.136/kWh |
| Pennsylvania (Philadelphia / Pittsburgh) | 4A | 4.39 h/day | 36° | 13.6°F | 90.7°F | $0.185/kWh |
| Rhode Island (Providence) | 5A | 4.31 h/day | 37° | 8.8°F | 87.1°F | $0.287/kWh |
| South Carolina (Columbia / Charleston) | 3A | 5.05 h/day | 31° | 24.3°F | 95°F | $0.146/kWh |
| South Dakota (Sioux Falls) | 6A | 4.75 h/day | 39° | -13°F | 89.8°F | $0.133/kWh |
| Tennessee (Nashville / Memphis) | 4A | 4.72 h/day | 33° | 14.7°F | 93°F | $0.129/kWh |
| Texas (North) (Dallas / Fort Worth) | 3A | 5.35 h/day | 30° | 22.8°F | 100.4°F | $0.148/kWh |
| Texas (Central / South) (Houston / Austin / San Antonio) | 2A | 5.15 h/day | 27° | 31.8°F | 96.1°F | $0.148/kWh |
| Texas (West) (El Paso) | 3B | 6.32 h/day | 29° | 25°F | 99.7°F | $0.148/kWh |
| Utah (Salt Lake City) | 5B | 5.42 h/day | 37° | 9.3°F | 96.6°F | $0.119/kWh |
| Vermont (Burlington) | 6A | 4.1 h/day | 40° | -8.7°F | 85.8°F | $0.218/kWh |
| Virginia (Richmond / Norfolk) | 4A | 4.78 h/day | 34° | 17.6°F | 92.8°F | $0.149/kWh |
| Washington (West) (Seattle / Tacoma) | 4C | 3.85 h/day | 43° | 25.9°F | 84.9°F | $0.124/kWh |
| Washington (East) (Spokane) | 5B | 4.55 h/day | 43° | 4.3°F | 92.5°F | $0.124/kWh |
| West Virginia (Charleston) | 4A | 4.32 h/day | 35° | 10.9°F | 89.2°F | $0.155/kWh |
| Wisconsin (Milwaukee / Madison) | 6A | 4.31 h/day | 39° | -6.5°F | 87.4°F | $0.176/kWh |
| Wyoming (Cheyenne) | 6B | 5.51 h/day | 37° | -6.2°F | 88.5°F | $0.127/kWh |
📐 Methodology & Data Provenance
This reference dataset compiles publicly accessible meteorological, solar radiation, and utility statistics into a standardized screening matrix. The following methodology outlines how each variable is defined, sourced, and applied in engineering calculations:
☀️ Solar Resource & Peak Sun Hours (PSH)
Definition: 1 Peak Sun Hour equals 1 hour of equivalent standard irradiance at 1,000 W/m² (1 PSH = 1 kWh/m²/day of cumulative daily irradiation).
Source: Derived from multi-year solar irradiance records in the NREL National Solar Radiation Database (NSRDB) and NREL PVWatts V8 modeling runs for south-facing surfaces.
Engineering Note: PSH is a first-order resource indicator. Actual array energy yield (kWh/yr) requires modeling array DC rating (kW), tilt/azimuth transposition, thermal cell degradation (power temperature coefficient), inverter efficiency, and system losses.
📐 Reference Fixed Solar Tilt Angle
Definition: The fixed module tilt angle (degrees from horizontal) oriented due south (180° azimuth) that maximizes annual cumulative energy capture.
Methodology: Derived from latitude-based transposition models accounting for atmospheric path length and regional seasonal solar clearness indices (typically latitude minus 2° to 5° across continental U.S. latitudes).
❄️ ASHRAE Climatic Design Conditions
Source: ASHRAE Handbook — Fundamentals (Chapter 14: Climatic Design Information).
99% Winter DB: Ambient dry-bulb temperature exceeded 99% of hours in a typical year (used for peak heating load sizing and cold-climate heat pump staging).
1% Summer DB: Ambient dry-bulb temperature exceeded only 1% of annual hours (used for peak sensible cooling sizing).
Location Specificity: Values are specific to the representative airport/weather station listed for each metro area and do not represent a uniform statewide figure.
⚡ U.S. EIA Electricity Rates
Source: U.S. Energy Information Administration (EIA), Electric Power Monthly (Table 5.6.A: Average Price of Electricity to Ultimate Customers by End-Use Sector).
Basis: State-level weighted average residential retail price ($/kWh).
Variability Note: Rates represent historical statewide averages. Local retail utility tariffs vary significantly based on time-of-use (TOU) schedules, tiered consumption tiers, and monthly fixed service fees.
Explore Interactive Calculators Using This Dataset
These interactive engineering calculators integrate solar irradiance data and ASHRAE design baselines for planning modeling: