What does this tool need?

Your location (or latitude), roof tilt and azimuth, and either total area & module efficiency or panel count & wattage. Optionally set shading, losses and electricity price.

Where does the solar resource come from?

It uses a simple, latitude-based Peak Sun Hours estimate suitable for planning/education. You can override with known local PSH or values from solar maps.

No. All calculations run locally in your browser.

Solar Energy Calculator — kWh/day & Savings

Friendly estimates for planning and awareness. Private by design — runs locally in your browser.

Inputs

Latitude (°) Azimuth (° from South/North) Azimuth offset (°) Roof tilt (°)

Peak Sun Hours (PSH) (kWh/m²/day) Estimate mode

Array Size — choose one method

Method Total array area (m²) Module efficiency (%)

Assumptions (optional)

System losses (%) Shading (% energy lost) Electricity price Price (per kWh)

Friendly estimate only. Real-world values vary with local climate, shading, equipment, wiring, temperature, and maintenance.

Results

How This Solar Calculator Works

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).

DC size from area: m² × efficiency × 1 kW/m² at STC (so 20 m² at 20% ≈ 4.0 kW DC).
DC size from panels: panel count × panel wattage.
Losses: inverter, wiring, mismatch, temperature, dirt (default 14%).
Shading: extra percentage energy loss (default 5%).

Tip: If you know your local “peak sun hours” already, switch PSH to Manual and paste it directly.

Understand Your Solar Potential: How We Estimate kWh/Day and Savings

This solar energy 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. 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, and a money value based on your chosen electricity price.

Peak Sun Hours (PSH): the core idea

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.

Tilt & Azimuth: why direction matters

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.

Array size: two simple ways to specify it

Area & efficiency: DC size ≈ area (m²) × module efficiency × 1 kW/m² at STC. For instance, 20 m² at 20% ≈ 4.0 kW DC.
Panels & wattage: DC size ≈ number of panels × panel nameplate wattage.

Either path resolves to a DC kW rating that the calculator uses to estimate energy.

Losses & shading: reality checks

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)

From kWh to savings

To translate energy into money, set your local price per kWh. The calculator reports estimated savings per day and per year. This is a simplified bill-offset view; actual savings vary with time-of-use rates, export tariffs, and how much energy you consume while the sun is shining.

What this tool is—and isn’t

Great for: early feasibility, classroom demos, homeowner curiosity, and quick comparisons between roof orientations or array sizes.
Not a final design: precise engineering should include detailed irradiance datasets, module temperature models, inverter clipping, row spacing (for ground mount), and local code considerations.

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.

FAQs

What’s a good tilt?

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.

How reliable is the auto PSH?

It’s a coarse average from latitude bands. For proposals, use a site-specific value (e.g., PV map or utility data).

Does this include batteries or export tariffs?

No. This is generation and bill-offset only. Storage and tariffs are highly site-specific.