Friendly estimate only. Real-world values vary with local climate, shading, equipment, wiring, temperature, and maintenance.
We estimate daily energy with a simple model: Energy ≈ PSH × Orientation factor × DC size × (1 − losses) × (1 − shading). PSH (kWh/m²/day) is auto-estimated from latitude, or you can paste a local value from a solar map. Orientation combines tilt and azimuth vs. “optimal” facing (South in the Northern hemisphere, North in the Southern).
Tip: If you know your local “peak sun hours” already, switch PSH to Manual and paste it directly.
This solar panel output calculator gives you a clear, non-technical estimate of how much electricity a rooftop or ground-mount array could produce and how that translates into bill savings, export income, and payback. The model is intentionally transparent. It uses a small set of inputs—location (latitude), tilt, azimuth, and array size—to estimate kWh per day, monthly and yearly totals, then applies your electricity price, export tariff, self-consumption, system cost, incentives, and degradation assumptions. If you do not know your system size yet, use the reverse calculator to estimate how many panels you need for a daily target or household offset.
Peak Sun Hours (kWh/m²/day) compresses a day’s varying sunlight into an equivalent number of “full-sun hours.” For example, 4.5 PSH means your panels receive the same energy as 4.5 hours at 1,000 W/m². The tool auto-estimates PSH from latitude for an annual average, which is great for planning and education. If you have a site-specific value from a solar resource map or past system data, switch to manual PSH and paste it in for a more tailored result.
Orientation affects how much of that sunlight lands on the panels over the year. A helpful rule of thumb is optimal tilt ≈ |latitude|. In the Northern Hemisphere, arrays produce the most when they face South (North in the Southern Hemisphere). The calculator combines tilt and azimuth into a single orientation factor using a smooth, cosine-based penalty, so non-perfect roofs don’t get “punished” unrealistically. You’ll see this factor reported so you understand exactly how it influenced your result.
Either path resolves to a DC kW rating that the calculator uses to estimate energy.
The reverse sizing mode starts with a target instead of a system size. Choose 10, 20, 30, or custom kWh/day, or size around your annual electricity use and target offset. The calculator estimates the required kW, number of panels, roof area, and expected kWh/day and kWh/year using your PSH, roof orientation, panel wattage, efficiency, losses, and shading assumptions.
Daily and yearly averages are useful, but real solar output changes through the year. Use annual average mode for a simple month-by-month breakdown, seasonal estimate mode for a lightweight privacy-friendly curve, or monthly PSH override mode if you have local solar-resource values. The results table highlights each month, plus the best month, worst month, and summer-versus-winter difference.
Real systems don’t convert every photon into AC power. Heat, wiring, mismatch, inverter efficiency, soiling, and other practical effects reduce energy. We group these as system losses (a default 14% is typical for many modern installations). You can also add a separate shading percentage for trees, chimneys, or seasonal obstacles. The tool multiplies everything together:
kWh/day ≈ PSH × Orientation factor × DC size × (1 − losses) × (1 − shading)
To translate energy into money, set your local price per kWh, self-consumption percentage, and export or feed-in tariff. The calculator splits generation into self-consumed and exported energy, then reports bill savings, export income, total annual value, net system cost, simple payback, and long-term gross and net value.
Use this calculator to understand the main levers—PSH, orientation, size, and losses—and to build intuition about how each one moves your kWh/day and potential savings. When you’re ready for a proposal, bring these numbers (and your manual PSH) to an installer for a site-specific design.
Cities that sit on the same latitude—like Barcelona, Atlanta, and Perth near 34°—tend to share similar annual Peak Sun Hours (~5 kWh/m²/day). Checking a “latitude twin” is a quick sanity check for your PSH entry.
NREL field tests show shingles under a solar array can stay 5–10°F cooler in summer because modules shade and vent the roof—so your attic gets a free climate assist.
Once panels shed snow, the bright blanket below can reflect up to 80% of sunlight back at the glass. That albedo bump sometimes offsets the cold-season days you lose to snow cover.
A roof that’s 30° off South (or North) only drops output by roughly 5–10%, but it stretches the generation curve later into the evening—handy if you run appliances after work.
High-altitude cities such as Denver or La Paz get an extra 5–7% irradiance boost per kilometre of elevation because thinner air scatters less light. Use a local PSH value for extra accuracy.
For annual energy, “optimal tilt” is roughly your latitude. The tool downweights output as you move away from optimal tilt or rotate away from South/North.
It’s a coarse average from latitude bands. For proposals, use a site-specific value (e.g., PV map or utility data).
Yes. Use the target sizing section to enter a daily kWh goal, or annual electricity use and a target offset. The tool estimates system kW, panel count, roof area, and expected annual output.
Yes. Monthly output can use the annual average, a seasonal estimate, or manual monthly PSH values for January through December.
It includes export or feed-in tariff value, but not battery storage dispatch. Battery economics depend on local tariffs, load timing, usable capacity, and backup requirements.
