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  4. PVWatts V8

PVWatts V8 (GET /api/pvwatts/v8)

PVWatts® Version 8 is is the current version of the PVWatts API. Updates from Version 6 include a bifacial module option, a new input for monthly irradiance losses, new inputs for specifying albedo, and updates to the photovoltaic module, inverter, and thermal effects models to use more detailed and industry-accepted algorithms. PVWatts V8 also updates the weather data to 2020 TMY data from the NREL National Solar Radiation Database (NSRDB) for locations covered by the database. (The NSRDB weather data used in PVWatts V6 is from around 2015.) This update provides production estimates based on the latest, state-of-the art models from NREL that may differ from the V6 estimates, depending on the location and inputs. From a coding perspective, PVWatts V8 replaces the pvwattsv5 compute module with pvwattsv8 so that the PVWatts Calculator, web API, and implementation of PVWatts in the System Advisor Model (SAM) all use the same underlying model. For a complete description of PVWatts V8, see the description on the PVWatts website.

NREL anticipates that the V8 API will run slightly slower than the V6 API due to upgraded models. Please contact pvwatts@nrel.gov if you find V8 is significantly slower or that the performance is impacting your product.

There is a forthcoming report containing a technical description of the model.

Request URL

GET /api/pvwatts/v8.format?parameters

Request Parameters

Parameter Required Value Description
format Yes
Type: string
Default: None
Options: json, xml

The output response format.
api_key Yes
Type: string
Default: None

Your developer API key. See API keys for more information.
system_capacity Yes
Type: decimal
Default: None
Range: 0.05 to 500000

Nameplate capacity (kW).
module_type Yes
Type: integer
Default: None
Options: 0, 1, 2

Module type.

Option Description
0 Standard
1 Premium
2 Thin film
losses Yes
Type: decimal
Default: None
Range: -5 to 99
System losses (percent).
array_type Yes
Type: integer
Default: None
Options: 0, 1, 2, 3, 4

Array type.

Option Description
0 Fixed - Open Rack
1 Fixed - Roof Mounted
2 1-Axis
3 1-Axis Backtracking
4 2-Axis
tilt Yes
Type: decimal
Default: None
Range: 0 to 90
Tilt angle (degrees).
azimuth Yes
Type: decimal
Default: None
Min: 0
Max: < 360
Azimuth angle (degrees).
address Depends
Type: string
Default: None

The address to use. Required if lat/lon or file_id not specified.
lat Depends
Type: decimal
Default: None
Range: -90 to 90

The latitude for the location to use. Required if address or file_id not specified.
lon Depends
Type: decimal
Default: None
Range: -180 to 180

The longitude for the location to use. Required if address or file_id not specified.
file_id Depends
Type: string
Default: none
Reference to a specific climate data file to use. Must be a valid id returned by the Solar Dataset Query V2 API. Required if lat/lon or address not specified.
dataset No
Type: string
Default: nsrdb
Options: nsrdb, tmy2, tmy3, intl

The climate dataset to use. Should not be passed in if using file_id to specify the climate data file.

Option Description
nsrdb

Gridded TMY data from the NREL National Solar Radiation Database (NSRDB). Datasets include: NSRDB PSM V3 GOES tmy-2020 3.2.0, NSRDB PSM V3 Himawari tmy-2020 3.2.0, and NSRDB PSM V4 Meteosat Prime Meridian tmy-2022 1.0.0
tmy2

TMY2 station data (see NSRDB 1961-1990 Archive)
tmy3

TMY3 station data (see NSRDB 1991-2005 Archive)
intl

PVWatts International station data
radius No
Type: integer
Default: 100

The search radius to use when searching for the closest climate data station (miles). Pass in radius=0 to use the closest station regardless of the distance.
timeframe No
Type: string
Default: monthly
Options: monthly, hourly
Granularity of the output response.
dc_ac_ratio No
Type: decimal
Default: 1.2
Range: must be positive

DC to AC ratio.
gcr No
Type: decimal
Default: 0.4
Range: 0.01 - 0.99

Ground coverage ratio.
inv_eff No
Type: decimal
Default: 96
Range: 90 - 99.5

Inverter efficiency at rated power.
bifaciality No
Type: decimal
Default: None
Range: 0 - 1

The ratio of rear-side efficiency to front-side efficiency. Typically a value between 0.65 and 0.9 provided on the bifacial module datasheeet. This is to account for the fact that photovoltaic cells on the rear of the module are usually less efficient than the cells on the front of the module. The bifaciality does not affect the solar irradiance on the rear of the module.
albedo No
Type: decimal or array of decimal
Default: None
Range: >0 and <1

Ground reflectance. A value of 0 would mean that the ground is completely non-reflective, and a value of 1 would mean that it is completely reflective. Specify either a pipe-delimited array of 12 monthly values or a single value to be used for all months.
use_wf_albedo No
Type: integer
Default: None
Options: 0, 1

Use hourly or subhourly albedo data from the weather file instead of the monthly albedo values, if available. 0 means do not use weather file albedo values, 1 means use weather file albedo values.
soiling No
Type: array of decimal
Default: None
Range: 0 - 100

Reduction in incident solar irradiance caused by dust or other seasonal soiling of the module surface that reduce the radiation incident on the subarray. Soiling losses cause a uniform reduction in the total irradiance incident on each subarray. Specify a pipe-delimited array of 12 monthly values.
callback No
Type: string
Default: None

Return the data using JSONP and the given callback function (only applicable when using the json format).

Response Fields

The response is composed of service-related informational fields and the results of the PVWatts simulation.

Field Value Description
inputs Type: collection The input parameters received in the request.
errors Type: array of strings Any error messages resulting from the request.
warnings Type: array of strings Any warning messages resulting from the request.
version Type: string The current version of the web service.
ssc_info Type: collection Information about the SSC library.
station_info Type: collection Information about the weather data used in the simulation. (see station info fields for more detail)
outputs Type: collection The data outputs from the simulation. (see output fields for more detail)


Station Info Fields

Field Value Description
lat Type: decimal Latitude of the climate station.
lon Type: decimal Longitude of the climate station.
elev Type: decimal Elevation of the climate station. (meters)
tz Type: decimal Timezone offset from GMT.
location Type: string ID of the climate station.
city Type: string City where climate station is located.
state Type: string State where climate station is located.
solar_resource_file Type: string Solar resource filename.
distance Type: integer Distance between the input location and the climate station. (meters)
weather_data_source Type: string Source of the weather data used in the simulation.


Output Fields

Field Value Description
poa_monthly Type: array of decimal Monthly plane of array irradiance values. (kWh/m2)

The array of values represents the value for each month, with the first element being for January and the last element being for December.
dc_monthly Type: array of decimal Monthly DC array output. (kWhdc)

The array of values represents the value for each month, with the first element being for January and the last element being for December.
ac_monthly Type: array of decimal Monthly AC system output. (kWhac)

The array of values represents the value for each month, with the first element being for January and the last element being for December.
ac_annual Type: decimal Annual AC system output. (kWhac)
solrad_monthly Type: array of decimal Monthly solar radiation values. (kWh/m2/day) The array of values represents the value for each month, with the first element being for January and the last element being for December.
solrad_annual Type: decimal Annual solar radiation values. (kWh/m2/day)
capacity_factor Type: decimal The ratio of the system's predicted electrical output in the first year of operation to the nameplate output, which is equivalent to the quantity of energy the system would generate if it operated at its nameplate capacity for every hour of the year. (AC-to-DC)
ac Type: array of decimal Hourly AC system output (only when timeframe=hourly). (Wac)
poa Type: array of decimal Hourly plane of array irradiance (only when timeframe=hourly). (W/m2)
dn Type: array of decimal Hourly beam normal irradiance (only when timeframe=hourly). (W/m2)
dc Type: array of decimal Hourly DC array output (only when timeframe=hourly). (Wdc)
df Type: array of decimal Hourly diffuse irradiance (only when timeframe=hourly). (W/m2)
tamb Type: array of decimal Hourly ambient temperature (only when timeframe=hourly). (C)
tcell Type: array of decimal Hourly module temperature (only when timeframe=hourly) (C)
wspd Type: array of decimal Hourly windspeed (only when timeframe=hourly). (m/s)
alb Type: array of decimal Hourly albedo values (only when timeframe=hourly).

Examples

JSON Output Format

GET /api/pvwatts/v8.json?api_key=DEMO_KEY&azimuth=180&system_capacity=4&losses=14&array_type=1&module_type=0&gcr=0.4&dc_ac_ratio=1.2&inv_eff=96.0&radius=0&dataset=nsrdb&tilt=10&address=boulder, co&soiling=12|4|45|23|9|99|67|12.54|54|9|0|7.6&albedo=0.3&bifaciality=0.7
{
  "inputs": {
    "api_key": "DEMO_KEY",
    "azimuth": "180",
    "system_capacity": "4",
    "losses": "14",
    "array_type": "1",
    "module_type": "0",
    "gcr": "0.4",
    "dc_ac_ratio": "1.2",
    "inv_eff": "96.0",
    "radius": "0",
    "dataset": "nsrdb",
    "tilt": "10",
    "address": "boulder, co",
    "soiling": [
      12.0,
      4.0,
      45.0,
      23.0,
      9.0,
      99.0,
      67.0,
      12.54,
      54.0,
      9.0,
      0.0,
      7.6
    ],
    "albedo": "0.3",
    "bifaciality": "0.7"
  },
  "errors": [],
  "warnings": [],
  "version": "8.0.0",
  "ssc_info": {
    "version": 275,
    "build": "Linux 64 bit GNU/C++ Oct  4 2022 03:10:07",
    "module": "pvwattsv8"
  },
  "station_info": {
    "lat": 40.0099983215332,
    "lon": -105.2600021362305,
    "elev": 1635.640014648438,
    "tz": -7.0,
    "location": "149190",
    "city": "",
    "state": "Colorado",
    "solar_resource_file": "149190.csv",
    "weather_data_source": "NSRDB PSM V3 GOES tmy-2020 3.2.0"
  },
  "outputs": {
    "ac_monthly": [
      320.4228876642905,
      384.8616364666353,
      321.3271515621691,
      461.0094975545317,
      554.600835450473,
      40.44452828685269,
      226.7508104582373,
      511.2267102793363,
      256.8889494651126,
      399.0896267699792,
      360.6690887453739,
      294.0619118014161
    ],
    "poa_monthly": [
      96.24926945531107,
      116.1349407270755,
      98.51940622925228,
      144.41773091741,
      183.8794484222849,
      15.66165708215378,
      77.02556424264554,
      173.1452731392307,
      84.65672810465938,
      127.5225461326769,
      111.2069066909127,
      88.32854384099618
    ],
    "solrad_monthly": [
      3.104815143719712,
      4.147676454538409,
      3.178045362233945,
      4.813924363913667,
      5.931595110396287,
      0.5220552360717927,
      2.484695620730502,
      5.585331391588086,
      2.821890936821979,
      4.113630520408932,
      3.706896889697091,
      2.849307865838586
    ],
    "dc_monthly": [
      336.9419000259236,
      403.7478814828723,
      339.0451574758127,
      484.2180320849528,
      582.0288887329309,
      48.66263077401924,
      242.1187483732162,
      536.8888804277215,
      272.1669926053272,
      419.1849677039804,
      378.8226598116249,
      309.3147603281601
    ],
    "ac_annual": 4131.353634504403,
    "solrad_annual": 3.604988741329917,
    "capacity_factor": 11.79039279253541
  }
}

XML Output Format

GET /api/pvwatts/v8.xml?api_key=DEMO_KEY&azimuth=180&system_capacity=4&losses=14&array_type=1&module_type=0&gcr=0.4&dc_ac_ratio=1.2&inv_eff=96.0&radius=0&dataset=nsrdb&tilt=10&address=boulder, co&soiling=12|4|45|23|9|99|67|12.54|54|9|0|7.6&albedo=0.3&bifaciality=0.7
<?xml version="1.0" encoding="UTF-8"?>
<response>
  <inputs>
    <api-key>DEMO_KEY</api-key>
    <azimuth>180</azimuth>
    <system-capacity>4</system-capacity>
    <losses>14</losses>
    <array-type>1</array-type>
    <module-type>0</module-type>
    <gcr>0.4</gcr>
    <dc-ac-ratio>1.2</dc-ac-ratio>
    <inv-eff>96.0</inv-eff>
    <radius>0</radius>
    <dataset>nsrdb</dataset>
    <tilt>10</tilt>
    <address>boulder, co</address>
    <soiling type="array">
      <soiling type="float">12.0</soiling>
      <soiling type="float">4.0</soiling>
      <soiling type="float">45.0</soiling>
      <soiling type="float">23.0</soiling>
      <soiling type="float">9.0</soiling>
      <soiling type="float">99.0</soiling>
      <soiling type="float">67.0</soiling>
      <soiling type="float">12.54</soiling>
      <soiling type="float">54.0</soiling>
      <soiling type="float">9.0</soiling>
      <soiling type="float">0.0</soiling>
      <soiling type="float">7.6</soiling>
    </soiling>
    <albedo>0.3</albedo>
    <bifaciality>0.7</bifaciality>
  </inputs>
  <errors type="array"/>
  <warnings type="array"/>
  <version>8.0.0</version>
  <ssc-info>
    <version type="integer">275</version>
    <build>Linux 64 bit GNU/C++ Oct  4 2022 03:10:07</build>
    <module>pvwattsv8</module>
  </ssc-info>
  <station-info>
    <lat type="float">40.0099983215332</lat>
    <lon type="float">-105.26000213623047</lon>
    <elev type="float">1635.6400146484375</elev>
    <tz type="float">-7.0</tz>
    <location>149190</location>
    <city></city>
    <state>Colorado</state>
    <solar-resource-file>149190.csv</solar-resource-file>
    <weather-data-source>NSRDB PSM V3 GOES tmy-2020 3.2.0</weather-data-source>
  </station-info>
  <outputs>
    <ac-monthly type="array">
      <ac-monthly type="float">320.4228876642905</ac-monthly>
      <ac-monthly type="float">384.8616364666353</ac-monthly>
      <ac-monthly type="float">321.32715156216915</ac-monthly>
      <ac-monthly type="float">461.00949755453166</ac-monthly>
      <ac-monthly type="float">554.600835450473</ac-monthly>
      <ac-monthly type="float">40.444528286852695</ac-monthly>
      <ac-monthly type="float">226.75081045823728</ac-monthly>
      <ac-monthly type="float">511.2267102793363</ac-monthly>
      <ac-monthly type="float">256.8889494651126</ac-monthly>
      <ac-monthly type="float">399.0896267699792</ac-monthly>
      <ac-monthly type="float">360.66908874537387</ac-monthly>
      <ac-monthly type="float">294.0619118014161</ac-monthly>
    </ac-monthly>
    <poa-monthly type="array">
      <poa-monthly type="float">96.24926945531107</poa-monthly>
      <poa-monthly type="float">116.13494072707546</poa-monthly>
      <poa-monthly type="float">98.51940622925228</poa-monthly>
      <poa-monthly type="float">144.41773091741</poa-monthly>
      <poa-monthly type="float">183.8794484222849</poa-monthly>
      <poa-monthly type="float">15.661657082153782</poa-monthly>
      <poa-monthly type="float">77.02556424264554</poa-monthly>
      <poa-monthly type="float">173.14527313923068</poa-monthly>
      <poa-monthly type="float">84.65672810465938</poa-monthly>
      <poa-monthly type="float">127.5225461326769</poa-monthly>
      <poa-monthly type="float">111.20690669091273</poa-monthly>
      <poa-monthly type="float">88.32854384099618</poa-monthly>
    </poa-monthly>
    <solrad-monthly type="array">
      <solrad-monthly type="float">3.1048151437197116</solrad-monthly>
      <solrad-monthly type="float">4.147676454538409</solrad-monthly>
      <solrad-monthly type="float">3.1780453622339446</solrad-monthly>
      <solrad-monthly type="float">4.813924363913667</solrad-monthly>
      <solrad-monthly type="float">5.9315951103962865</solrad-monthly>
      <solrad-monthly type="float">0.5220552360717927</solrad-monthly>
      <solrad-monthly type="float">2.4846956207305015</solrad-monthly>
      <solrad-monthly type="float">5.5853313915880864</solrad-monthly>
      <solrad-monthly type="float">2.8218909368219793</solrad-monthly>
      <solrad-monthly type="float">4.113630520408932</solrad-monthly>
      <solrad-monthly type="float">3.706896889697091</solrad-monthly>
      <solrad-monthly type="float">2.849307865838586</solrad-monthly>
    </solrad-monthly>
    <dc-monthly type="array">
      <dc-monthly type="float">336.9419000259236</dc-monthly>
      <dc-monthly type="float">403.7478814828723</dc-monthly>
      <dc-monthly type="float">339.04515747581274</dc-monthly>
      <dc-monthly type="float">484.21803208495277</dc-monthly>
      <dc-monthly type="float">582.0288887329309</dc-monthly>
      <dc-monthly type="float">48.66263077401924</dc-monthly>
      <dc-monthly type="float">242.1187483732162</dc-monthly>
      <dc-monthly type="float">536.8888804277215</dc-monthly>
      <dc-monthly type="float">272.16699260532715</dc-monthly>
      <dc-monthly type="float">419.1849677039804</dc-monthly>
      <dc-monthly type="float">378.82265981162493</dc-monthly>
      <dc-monthly type="float">309.3147603281601</dc-monthly>
    </dc-monthly>
    <ac-annual type="float">4131.353634504403</ac-annual>
    <solrad-annual type="float">3.6049887413299166</solrad-annual>
    <capacity-factor type="float">11.79039279253541</capacity-factor>
  </outputs>
</response>

Rate Limits

Standard rate limits apply. No more than 1,000 requests may be made in any hour.

Errors

Standard errors may be returned. In addition, the following service-specific errors may be returned:

HTTP Status Code Description
422 Unprocessable Entity - One or more parameters did not pass validation, or a parameter may be missing. Check the errors section of the response to see how the request should be modified to address the error.
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