Solar panel power output calculator
Sunlight of 1000 W/m² on a 1.6 m² panel at 20% efficiency gives 320 W, or 0.32 kW. Use it to check a datasheet claim or size an array before adding real-world losses. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Irradiance
- 1,000
- Panel area
- 1.6
- Efficiency
- 0.2
- Irradiance w per m2
- 1,000
- Panel area m2
- 1.6
- Power w
- 320
- Power kw
- 0.32
Sizing a photovoltaic array or checking a nameplate claim starts with a transparent product of three numbers: plane-of-array solar irradiance in watts per square metre, active panel area in square metres, and module conversion efficiency as a fraction between zero and one. This solar panel power output calculator multiplies those inputs into instantaneous DC power in watts and kilowatts under a simple conversion model that every installer, teacher, and spreadsheet already uses. Standard test condition reference irradiance of one thousand watts per square metre with twenty percent efficiency on a one-point-six square metre module yields three hundred twenty watts—easy to audit. Negative panel area, negative efficiency, or efficiency above one hundred percent is rejected as invalid input so automation never stores a nonsense negative or super-unity power figure.
What photovoltaic power output means and how the product is built
Instantaneous photovoltaic power answers a practical question: given the solar irradiance incident on the module plane, the active area of the panel, and the conversion efficiency of the cells and packaging, how many watts of DC electrical power does the module produce under a simple linear model? The textbook product is power in watts equals irradiance in watts per square metre times panel area in square metres times efficiency as a dimensionless fraction.
Irradiance is the plane-of-array flux you measure with a pyranometer or take from a weather file or standard test condition table; one thousand watts per square metre is the classic STC reference used on most datasheets. Panel area is the active photovoltaic surface in square metres, not the gross roof footprint of the rack unless those two coincide.
Efficiency is the fraction of incident power converted to DC electricity—send zero point two for twenty percent, not twenty, because values above one are rejected as physically impossible for a passive conversion ratio in this model. When irradiance is zero the product is zero power, which is correct for night or full shade under this idealised model. When area is zero the product is zero power as well.
The capability returns both watts and kilowatts so small modules and multi-kilowatt strings share the same contract without client-side unit conversion bugs.
What you enter, what you get, what is refused
Irradiance must not be negative. Panel area must not be negative—negative area fails with a clear message that panel area cannot be negative. Efficiency must not be negative and must not exceed one; sending twenty instead of zero point two for twenty percent is a common mistake and is rejected with a message that efficiency cannot exceed one and that you should use a fraction.
Example: the same area and efficiency under five hundred watts per square metre yields one hundred sixty watts. Validation failures are not billed. The capability does not convert percent to fraction for you if you send values above one, does not look up weather stations over the network, and does not invent system losses—supply the plane-of-array irradiance and the efficiency you trust.
Who checks panel output this way
Installers and design tools need a deterministic oracle that turns nameplate area and efficiency plus a chosen irradiance into a watt figure for quick quotes without embedding ad-hoc spreadsheets in every service. STEM classrooms and energy literacy sites want a live solar panel power output calculator students can audit against the product irradiance times area times efficiency, including deliberate rejection of efficiency above one hundred percent. Home energy dashboards compare winter and summer irradiance on the same panel by swapping only the irradiance field while holding area and efficiency fixed.
Failed validation does not consume balance. Pin rounded outputs in tests, document whether your irradiance is STC or measured plane-of-array, and you get reproducible photovoltaic power numbers for education, quoting, and product UX without standing up a full PV simulation stack.
What you can do with it
Quick module nameplate checks
Multiply STC irradiance, module area, and datasheet efficiency to verify claimed watts before ordering panels.
Classroom PV product demos
Let students change irradiance, area, and efficiency and see ordered watts, including rejection when efficiency exceeds one.
Seasonal irradiance comparisons
Hold panel area and efficiency fixed and swap irradiance to compare summer versus winter instantaneous DC power.
FAQ
What happens if efficiency is greater than one?
Efficiency must be a fraction between 0 and 1 inclusive—use 0.2 for 20%, not 20. Invalid input is not billed.
What irradiance should I use for STC?
Standard test condition reference irradiance is commonly 1000 W/m². For real-site estimates, supply measured or modelled plane-of-array irradiance instead.
How many watts does a 1.6 m² panel produce at 1000 W/m²?
At 20% efficiency, 1000 W/m² on 1.6 m² gives 320 W, or 0.32 kW. A different efficiency scales the result in direct proportion.
Does the result include temperature, inverter or dirt losses?
No. It is the ideal DC power from irradiance, area and efficiency. Temperature effects, inverter losses, soiling, mismatch and sun angle are left for you to apply before or after the calculation.
Which area should I enter, the panel or the whole roof?
Enter the active solar surface of the module in square metres, not the roof space taken up by the mounting rack, unless the two happen to be the same.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/earth/solar-power-output \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"irradiance":1000,"panel_area":1.6,"efficiency":0.2}'const res = await fetch("https://api.kit.forhosting.com/earth/solar-power-output", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"irradiance": 1000,
"panel_area": 1.6,
"efficiency": 0.2
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/earth/solar-power-output",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"irradiance": 1000,
"panel_area": 1.6,
"efficiency": 0.2
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/earth/solar-power-output", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"irradiance":1000,"panel_area":1.6,"efficiency":0.2}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"irradiance":1000,"panel_area":1.6,"efficiency":0.2}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/earth/solar-power-output", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"irradiance": 1000,
"panel_area": 1.6,
"efficiency": 0.2
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "earth.solar_power_output",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
What photovoltaic power output means and how the product is built
Temperature coefficients, inverter losses, soiling, mismatch, and angle-of-incidence modifiers are deliberately outside this endpoint: you apply those factors yourself before or after the call if your workflow needs them.
Input contract, response fields, and error behaviour
POST a JSON body with three required finite numbers: irradiance in watts per square metre (aliases: solar_irradiance, g, g_t, irradiance_w_per_m2, poa_irradiance), panel_area in square metres (aliases: area, panel_area_m2, a, surface_area), and efficiency as a fraction from zero to one inclusive (aliases: eta, conversion_efficiency, module_efficiency, eff). Each field may arrive as a JSON number or as a numeric string; missing fields, empty strings, and non-finite values fail with invalid_input naming the field. On success the body echoes irradiance_w_per_m2, panel_area_m2, and efficiency after validation, plus power_w, power_kw (watts divided by one thousand), and a short formula string you can display next to the result. Example: irradiance one thousand, panel_area one point six, efficiency zero point two yields power_w three hundred twenty and power_kw zero point three two.
Where a solar panel power output API earns its keep
Automation pipelines that size arrays or validate sensor feeds call the prepaid API with the same pure module so browser demos and backend checks never diverge.
Technical questions
How is solar panel power output calculated?
Send irradiance (W/m²), panel_area (m²), and efficiency as a fraction in [0, 1]. The API returns power_w = irradiance × panel_area × efficiency and power_kw = power_w / 1000.
Can panel area be negative?
No. Negative panel_area is rejected as invalid_input with a message that panel area cannot be negative.
What does the solar panel power output calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.