Solar Panel Output Calculator
Estimate the energy output and cost savings of a solar panel system. Enter panel count, wattage, peak sun hours, system losses, and electricity rate to get daily, weekly, monthly, yearly, and 25-year lifetime kWh production plus savings, CO2 offset, and battery sizing.
Input
STC rated wattage per panel (typically 300–450W)
Average peak-sun-hours for your location (3–7 in most regions)
Combined losses from inverter, wiring, shading, soiling, temperature (default 15%)
Your cost per kWh from the utility (used for savings estimate)
Optional — your household's average daily consumption for battery sizing and offset %
Output
| Period | Energy (kWh) | Savings ($) |
|---|---|---|
| No data yet | ||
Guides
Estimate how much electricity a solar array will produce — and what it will save you — before you commit to a system. Enter your panel count, panel wattage, local peak sun hours, expected system losses, and electricity rate, and the calculator returns daily, weekly, monthly, yearly, and 25-year lifetime energy output alongside the matching dollar savings.
How it works
The core estimate is simple and industry-standard:
- System size (kW) = number of panels × panel wattage ÷ 1000.
- Daily output (kWh) = system size × peak sun hours × (1 − system losses).
- Weekly, monthly (× 30.44 days), and yearly (× 365 days) figures scale from the daily number.
- Lifetime output sums 25 years of production, applying 0.5% annual panel degradation each year.
Savings for every period are the energy produced multiplied by your electricity rate ($/kWh).
Inputs explained
- Number of panels / Panel wattage — multiply to get your array's nameplate DC capacity. Most residential panels are 300–450W.
- Peak sun hours — not daylight hours, but the equivalent hours of full 1000 W/m² sun your location receives per day. Typical values run 3–7 depending on region and season.
- System losses — a single derate factor covering inverter efficiency, wiring, shading, soiling, and temperature. 15% is a common default (the PVWatts standard is around 14%).
- Electricity rate — your utility's cost per kWh, used to translate production into savings.
- Daily usage (optional) — your household's average daily consumption. Supply it to size a one-day backup battery and see what percentage of your usage the system offsets.
Extra outputs
- System size in kW (DC nameplate).
- CO₂ offset — yearly avoided emissions, using a grid average of 0.4 kg CO₂ per kWh, shown in kilograms and tonnes.
- Battery size — the usable capacity needed to cover one day of your usage at 80% depth of discharge.
- Daily consumption offset — the share of your daily usage the array covers, with any surplus flagged.
How accurate is this?
It's a planning estimate, not a bankable design. Real output depends on panel orientation, tilt, local weather, shading over the day, and inverter clipping. Treat the numbers as a well-grounded starting point, then confirm with a site-specific tool like NREL's PVWatts or a professional quote.
Is my data private?
Yes. Every calculation runs entirely in your browser — nothing you type is uploaded or stored.
Use it from code
From 3 credits per callREST API
curl -X POST https://api.iotools.cloud/v1/tool/solar-panel-output-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"panels": "10",
"wattage": "400",
"sunHours": "4.5",
"systemLoss": "15",
"rate": "0.15",
"dailyUsage": "30"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `solar-panel-output-calculator` tool (Solar Panel Output Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.