Solar planning

Solar Panel Output Calculator

Estimate monthly and annual solar panel output for your location using system size, panel details, orientation, and a location-aware PVWatts V8 model.

Estimate solar production

100% Private & Ad-Free•No Sign-Up or Email Required•Instant Browser-Local Computation

⚡ 1-Click Autofill: Top 5 Solar Setups

📍 Regional NREL Solar Irradiance Presets

Select your state to load official NREL annual peak sun hours, optimal tilt angle, and geographic coordinates.

State / Metro Weather Station

☀️ Peak Sun Hours

5.62 kWh/m²/d

📐 Optimal Tilt

31° fixed

⚡ EIA Grid Rate

$0.315 /kWh

📊 Solar Panel Daily & Annual AC kWh Yield Matrix (by Peak Sun Hours)

Estimated AC electricity generated across standard DC array capacities factoring in 14% NREL PVWatts system losses.

DC Array Capacity	3.5 PSH (Pacific NW)	4.5 PSH (Midwest/NE)	5.5 PSH (South/Texas)	6.5 PSH (Desert SW)	Est. Annual (4.5 PSH)
400 W (1x Residential Module)	1.2 kWh/day	1.5 kWh/day	1.9 kWh/day	2.2 kWh/day	551 kWh/yr
1.2 kW (3x Modules / RV / Shed)	3.5 kWh/day	4.5 kWh/day	5.5 kWh/day	6.6 kWh/day	1,657 kWh/yr
4.0 kW (10x Modules / Townhouse)	11.8 kWh/day	15.1 kWh/day	18.5 kWh/day	21.8 kWh/day	5,518 kWh/yr
6.0 kW (15x Modules / Mid Home)Most Common	17.6 kWh/day	22.7 kWh/day	27.7 kWh/day	32.8 kWh/day	8,278 kWh/yr
10.0 kW (25x Modules / All-Electric)	29.4 kWh/day	37.8 kWh/day	46.2 kWh/day	54.6 kWh/day	13,797 kWh/yr
15.0 kW (38x Modules / Estate & EV)	44.1 kWh/day	56.7 kWh/day	69.3 kWh/day	81.9 kWh/day	20,695 kWh/yr

Assumes fixed equator-facing tilt matching regional latitude, 0.86 composite derate factor (soiling, inverter, wiring), and -0.35%/°C temperature coefficient.Source: NREL PVWatts V8 / IEC 61724

Engineering WalkthroughGoverned by NREL PVWatts V8 / IEC 61724

How to Calculate Solar Panel AC Electricity Output (Step-by-Step)

How to calculate hourly, daily, and annual photovoltaic AC energy production step-by-step using NREL PVWatts standards.

Determine Total DC Nameplate Array Capacity

Multiply the individual solar panel STC nameplate wattage by the total number of installed modules to find peak DC kilowatts ($P_{\text{dc,STC}}$).

P_{\text{dc}} = \frac{N_{\text{modules}} \times P_{\text{module,watts}}}{1000}

💡 Standard Example: 15 modules of 400 Watts each = (15 × 400) / 1,000 = 6.0 kW DC capacity.

Lookup Regional Solar Insolation (Peak Sun Hours)

Retrieve local annual average Peak Sun Hours (PSH) from NREL National Solar Radiation Database (NSRDB) representing 1,000 W/m² equivalent hours.

\text{PSH} = \frac{\text{Daily Solar Irradiation (Wh/m}^2)}{1000\text{ W/m}^2}

💡 Standard Example: Austin, Texas receives an annual average of 5.15 Peak Sun Hours per day.

Apply System Derate Factors & Inverter Efficiency

Multiply DC nameplate capacity by regional PSH and the composite system derating factor (typically 0.84 to 0.86 accounting for thermal degradation, soiling, wiring losses, and DC-to-AC conversion).

E_{\text{daily,kWh}} = P_{\text{dc}} \times \text{PSH} \times \eta_{\text{system}}

💡 Standard Example: 6.0 kW × 5.15 PSH × 0.86 = 26.57 kWh per day (~9,699 kWh per year).

How to Calculate Your Solar Panel Output

Enter Location: Input your city or exact latitude/longitude coordinates to pull historical solar insolation datasets.
Select System Capacity (kW): Choose total system size in kilowatts or calculate from panel count and wattage (e.g. 20 panels × 400W = 8.0 kW).
Set Roof Pitch & Orientation: Enter roof tilt angle and compass azimuth (180° South is standard).
Review Monthly Yield Breakdown: Analyze expected monthly generation curves to plan winter vs summer energy balances.

⚡

Solar PV Power Path & AC Conversion Architecture

Solar irradiance converted to DC power, managed by MPPT, stored in battery reserves, and inverted to AC power.

☀️SourceSolar PV ArrayDC Generation (Vmp / Imp)

⚡RegulationMPPT ControllerDC-to-DC Optimization (98% eff)

🔋StorageBattery BankLiFePO4 / AGM Storage (Wh / Ah)

🔄ConversionInverterDC to AC Conversion (90% eff)

🏠DemandAC Household Loads120V / 240V Appliances

Engineering Principle: System round-trip efficiency typically ranges from 82% to 88% due to wiring, MPPT, and inverter conversion losses.

Solar Panel System Production Reference Matrix

Estimated annual and monthly electricity generation across standard residential system capacities and regional solar insolation levels:

Estimated annual & monthly AC generation (14% typical system losses)
System Size (kW DC)	Panel Count (400W)	Moderate Sun (3.5 PSH / ~1,200 kWh/kW-yr)	High Sun (5.0 PSH / ~1,650 kWh/kW-yr)
4.0 kW System	10 panels (~200 sq ft)	~4,800 kWh / yr (~400 kWh/mo)	~6,600 kWh / yr (~550 kWh/mo)
6.0 kW System	15 panels (~300 sq ft)	~7,200 kWh / yr (~600 kWh/mo)	~9,900 kWh / yr (~825 kWh/mo)
8.0 kW System	20 panels (~400 sq ft)	~9,600 kWh / yr (~800 kWh/mo)	~13,200 kWh / yr (~1,100 kWh/mo)
12.0 kW System	30 panels (~600 sq ft)	~14,400 kWh / yr (~1,200 kWh/mo)	~19,800 kWh / yr (~1,650 kWh/mo)

Solar AC Energy Yield & System Sizing Formulas

Estimates practical solar electricity output based on DC nameplate capacity, regional irradiance (solar insolation), and derating factors including wiring, inverter efficiency, and temperature coefficients.

01Daily_kWh = System_Size_kW × Peak_Sun_Hours × (1 - System_Losses)

Variable Definitions

System_Size_kWArray DC Nameplate Rating(kW): Total panel wattage sum in kilowatts (e.g. 15 × 400W panels = 6.0 kW).
Peak_Sun_HoursDaily Solar Insolation (PSH)(hours/day): Equivalent hours per day at standard solar irradiance of 1,000 W/m² (typically 3.5 to 5.5 hours).
System_LossesAggregate Derate Factor(fraction): Standard combined losses for soiling, shading, wiring, inverter AC conversion, and thermal derate (typically 14% to 18%).

Engineering Notes & Standards

NREL PVWatts V8 performs hourly solar irradiance simulations using typical meteorological year (TMY3/NSRDB) climate records.
Specific Yield (kWh/kWp/year) measures how many kilowatt-hours each kilowatt of installed solar generates annually.

Frequently Asked Questions (FAQ)

How much electricity does a 400-Watt solar panel produce per day?

In an area with 4.5 peak sun hours per day, a 400W panel produces approximately 1.4 to 1.6 kilowatt-hours (kWh) of usable AC electricity per day after accounting for normal wiring and inverter conversion losses (approx 14%). Over a full year, one 400W panel produces between 500 and 650 kWh.

How many solar panels do I need to power an average home?

The average US household consumes approximately 880 to 900 kWh per month (around 10,500 kWh annually). To offset 100% of this consumption in an average sun region, you would need a 7 kW to 8 kW solar array, which translates to roughly 18 to 22 modern 400-Watt solar panels.

Why does solar production drop in winter?

Winter solar production decreases due to shorter daylight hours, lower solar altitude (sun angle), increased cloud cover, and snow coverage. In northern latitudes, a system may produce 60% to 70% less energy in December than in June.

What are standard solar system losses (derate factors)?

Typical grid-tied residential solar arrays experience combined losses of 14% to 18%. This includes DC wiring resistance (~2%), inverter DC-to-AC conversion losses (~3%–4%), panel soiling and dust (~2%), module mismatch (~1%–2%), and high temperature power derating (~4%–8% during hot summer afternoons).