See every shadow on the roof before a single panel goes up.

Lekker Sun is a web-based designer for solar PV and battery systems. You place the roofs, trees and neighbouring buildings of a site on satellite imagery, and it works out how much shade falls on each panel through the year, how much energy the system will produce, how a battery will be used, and what the system will save. It ends with a report you can print or send to a client.

Solar installers and system designers who need to check a roof before quoting, and homeowners or business owners who want to understand what a proposed system will do. It works for sites anywhere in the world: times follow the site's local time zone, and you can use built-in usage patterns for homes and small businesses or import your own meter data.

Every half hour of a typical day in each month, it traces a ray towards the sun from six points on every panel. Buildings, roofs and poles block the ray completely. Tree crowns let some light through, depending on the tree's shape and how dense its foliage is. The result is the share of each panel in shade at each time, a month-by-hour shading grid, and the yearly energy lost to shade for each array.

Flat, gable, hip and shed (skillion) roofs, at any size, pitch, eave height and rotation. An array placed on a pitched roof takes the roof's pitch as its tilt. With Snap to roof face ticked, it also turns to face the slope it sits on. On flat roofs and on the ground you set the tilt and direction yourself.

Lekker Sun fetches long-term monthly irradiation for the site from NASA POWER, and from the European Commission's PVGIS if NASA POWER is unavailable. You can also type in your own monthly values, for example from the Global Solar Atlas. Without any data it uses a standard clear-sky model with a typical clearness factor.

Yes. It checks the string's open-circuit voltage at the site's coldest temperature against the inverter's maximum DC voltage, the MPP voltage against the MPPT window in hot and cold conditions, MPPT current and short-circuit current limits, the DC-to-AC ratio, the battery bank voltage against the inverter's battery port, and charge and discharge currents.

It shows how much of your electricity a battery can supply from stored solar, half hour by half hour, for typical summer and winter weeks and across the year. It does not simulate specific outage or load-shedding schedules, so for backup sizing also add up the essential loads you need to run during an outage and how long the outages last.

Yes. Upload a CSV with timestamped readings at 15, 30 or 60-minute intervals, in kWh per interval or average kW. Lekker Sun builds a typical day for each month from it and updates the monthly consumption. You can also upload one typical day of hourly usage per month.

No. The designer is free to use without an account and keeps your project in your browser, and you can export it as a file at any time. Accounts come with the Pro plan, which adds saving projects on the Lekker Sun server, your logo on reports and no ads.

They are design estimates. Production uses a clear-sky model scaled to monthly irradiation for a typical day in each month, with a flat 15% allowance for system losses. Panel temperature losses, string mismatch and battery replacement are not modelled. Have a qualified, registered installer confirm the design before you buy or install anything.