M
API Matrix

PVWatts API

⭐ Beginner's Pick Environment / API Key Intermediate HTTPS
Varies by plan (check documentation)
72 Score
Grade B
Visit Official Site Compare Alternatives

Overview

PVWatts is a NREL (National Renewable Energy Laboratory) API that estimates the energy production of grid-connected photovoltaic (solar panel) systems anywhere in the world. It requires a free API key from developer.nrel.gov and accepts system parameters like capacity, tilt, and azimuth to return annual and monthly energy output estimates. It is widely used by solar installers, researchers, and green energy app developers.

💡

Beginner Tip

Get a free API key instantly at developer.nrel.gov — no approval needed. The minimum required parameters are system_capacity (kW), azimuth, tilt, array_type, module_type, losses, and a lat/lon location; start with default tilt and azimuth values for your latitude and the API will return estimated kWh per year.

Available Data

PVWatts data via REST API
JSON-formatted response data
Requires API key authentication

Example Response

JSON Response 
{
  "id": "Dwu85P9SOIk",
  "urls": {
    "full": "https://images.unsplash.com/photo-...",
    "regular": "https://images.unsplash.com/photo-...?w=1080",
    "thumb": "https://images.unsplash.com/photo-...?w=200"
  },
  "width": 4000,
  "height": 3000,
  "user": {
    "name": "John Doe",
    "username": "johndoe"
  }
}

Field Reference

outputs.ac_annual Estimated annual AC energy production in kilowatt-hours (kWh) for the specified solar system
outputs.ac_monthly Array of 12 monthly AC energy production values in kWh, from January to December
outputs.solrad_annual Annual average solar irradiance in kWh/m²/day for the specified location
outputs.capacity_factor Ratio of actual energy output to theoretical maximum output, expressed as a percentage
station_info.lat Latitude of the weather station used for solar resource data in the calculation
errors List of validation error messages if any input parameters are invalid; empty array means no errors

Implementation Example 

// ⚠️ Note: This URL may be a documentation page. Check official docs for actual API endpoint.
const url = "https://developer.nrel.gov/docs/solar/pvwatts/v6/";
// Replace headers or query params with the values required by this API.
const response = await fetch(url, {
  headers: {
  "X-API-Key": "YOUR_API_KEY"
  }
});
if (!response.ok) throw new Error(`Request failed: ${response.status}`);
const data = await response.json();
console.log(data);

What Can You Build?

Note: These code examples are AI-generated and unverified. Always refer to the official API documentation for accurate usage.

Common Errors & Troubleshooting

403 Forbidden / OVER_RATE_LIMIT You have exceeded the free tier rate limit of 1,000 requests per hour
✓ Cache results for the same location and system parameters rather than re-requesting; results do not change in real time
Errors array with "invalid value" messages One or more system parameters are outside the valid range (e.g. tilt must be 0-90)
✓ Check the PVWatts v6 docs for valid parameter ranges; azimuth is 0-360, tilt is 0-90, losses must be less than 100
400 Missing required parameter A required parameter like system_capacity or lat/lon is missing from the request
✓ Include all required parameters: system_capacity, azimuth, tilt, array_type, module_type, losses, and either lat/lon or an address

Matrix Score Breakdown

🌐 Reachability 30/30
⚡ Speed 5/20
🔒 Security 15/15
🛠 Developer XP 12/20
✓ Reliability 10/15

Partially tested on Apr 5, 2026

Technical Specifications

Auth API Key
HTTPS REQUIRED
CORS UNKNOWN
Category Environment
Difficulty Intermediate
Verified: 2026-04-07

Similar APIs

View All →

BreezoMeter Pollen

82

BreezoMeter Pollen API (now part of Google Maps Platform) provides daily pollen forecast data including pollen type, index values, and risk levels for a specific geographic location.

API Key Intermediate HTTPS

Carbon Interface

87

Carbon Interface API calculates estimated CO2 emissions for common activities such as electricity usage, flights, vehicle travel, and shipping.

API Key Intermediate HTTPS

Climatiq

87

Climatiq is an API for calculating carbon emissions and environmental footprint across a wide range of activities including travel, energy use, and shipping.

API Key Intermediate HTTPS

Cloverly

0

Cloverly provides programmatic access to api calculates the impact of common carbon-intensive activities in real time via REST API.

API Key Intermediate HTTPS

IQAir

⭐ Beginner's Pick
37

IQAir API provides real-time air quality index (AQI) data and weather conditions for cities and stations worldwide, powered by the IQAir sensor network.

API Key Intermediate HTTPS