One peak sun hour = 1 kWh/m² of solar energy received. A 6kW system in Phoenix (6.57 peak sun hours/day) generates approximately 6 × 6.57 × 365 × 0.80 = 11,482 kWh/year. Values are annual averages from NASA POWER (ALLSKY_SFC_SW_DWN parameter). Use the zip calculator above for your precise location.
Annual savings shown at 14¢/kWh US avg electricity price. Source: NASA POWER ALLSKY_SFC_SW_DWN. Use zip code calculator for your exact location.
Plug-in solar is broadly legal across the United States under NEC Article 705 (Interconnected Electric Power Production Sources). Most states allow systems up to 2kW without complex utility approval — typically just a simple utility notification form. Unlike the UK (legalisation underway) or Germany (formal Balkonkraftwerk registration), the US has minimal regulatory friction for small plug-in systems.
The 30% Federal ITC also applies to home solar, reducing effective system costs significantly — a $800 plug-in kit costs effectively $560 after the tax credit. The US balcony solar market is estimated at 1–3 million deployed systems, largely untracked due to low registration requirements.
The USA is the most permissive of the three markets. Germany (Balkonkraftwerk) has formal registration and 435,000+ systems. The UK is behind both, with legalisation expected in 2026. The US leads on irradiance too — the Southwest averages 5–7 peak sun hours/day vs 2–3 for the UK and Germany.
| Factor | 🇺🇸 USA | 🇩🇪 Germany | 🇬🇧 UK |
|---|---|---|---|
| Plug-in legal? | Yes (NEC 705) | Yes (800W) | 2026 expected |
| Max size | Up to 2kW | 800W AC | 800W (planned) |
| Registration | Utility notify | Simple online | G98 (planned) |
| Market size | 1–3M est. | 435k+ systems | Pre-commercial |
| Peak sun hrs/day | 3.5–7.5 | 2.5–3.5 | 2.2–3.2 |
| Tax incentive | 30% Fed ITC | Feed-in tariff | SEG + 0% VAT |
| Payback | 2–4 years | 3–5 years | 3–6 years |
In 2025, utility-scale solar power generation totalled 296,000 GWh — 34% more than in 2024. Total US solar including small-scale reached 388,800 GWh. Texas set a new ERCOT solar peak record 12 times in early 2025 — the latest being 26,741 MW on 11 April 2025, providing 50.4% of ERCOT's power.
| Milestone | Value | Date/Source |
|---|---|---|
| ERCOT (Texas) peak | 26,741 MW | 11 Apr 2025 |
| CAISO (California) peak | 20,818 MW | 11 Apr 2025 |
| PJM (East) peak | 11,736 MW | 17 Apr 2025 |
| MISO (Midwest) peak | 12,530 MW | 16 Apr 2025 |
| 2025 utility-scale gen. | 296,000 GWh | Full year (EIA) |
| 2025 total solar (incl. small) | 388,800 GWh | Full year (EIA) |
| 2025 wind + solar share | 17% | Full year (EIA) |
| Installed capacity (end-2024) | 239 GW | EIA + USGS |
| 2026 planned additions | 43.4 GW | EIA Feb 2026 |
California and Texas together account for ~33% of US utility-scale solar. In 2026, Texas alone plans 17.4 GW of new capacity additions — nearly 40% of the national total. By 2030, solar is expected to be the single largest source of US electricity.
| State | Installed | Top cities for solar |
|---|---|---|
| California | ~21 GW | Los Angeles, San Diego, Fresno |
| Texas | ~19 GW | Dallas, San Antonio, Houston |
| Florida | ~10 GW | Miami, Orlando, Tampa |
| Arizona | ~8.5 GW | Phoenix, Tucson, Scottsdale |
| Nevada | ~5 GW | Las Vegas, Reno, Henderson |
| New York | ~4 GW | Buffalo, Albany, Long Island |
| New Jersey | ~4 GW | Newark, Trenton, Princeton |
| North Carolina | ~4 GW | Charlotte, Raleigh, Durham |
Live generation data from api.eia.gov — the US Energy Information Administration's free public API. Form 930 collects hourly data from 64 balancing authorities. Fuel type SUN = solar. Respondent US48 = all Lower 48 states combined. ↗
Zip to GPS via Zippopotam.us (free, no key). NASA POWER returns ALLSKY_SFC_SW_DWN parameter — all-sky shortwave downward irradiance in kWh/m²/day = peak sun hours. Same data used by NREL's PVWatts. ↗
Sol the mascot adjusts expression, cheeks, ray spin and bounce based on current generation as a % of the US installed capacity (~120 GW practical max output). Seven mood states from night to record-breaking.
Regional live data from the 8 EIA balancing authority regions: ERCOT (Texas), CAISO (California), PJM (East/Midwest), MISO (Mississippi), SWPP (Great Plains), SE (Southeast), ISNE (New England), NYIS (New York).
The United States solar data hub — live national generation via the EIA API, zip code solar calculators using NASA POWER satellite data, peak sun hours for all 50 states, balcony solar USA guide, and US solar records. All data is free and open.