WinterWatt Off-Grid Sizing

Site

Latitude °N

Altitude m

Array tilt °

Azimuth ° from S

Design month

Clear-sky index 0-1

Terrain horizon — skyline height, degrees

East °

South °

West °

Ground albedo

Load and storage

Daily load kWh/day

Autonomy days

Usable depth %

System efficiency %

Module Wp

Installed array kWp

Generator and cable

Fuel rate l/kWh

Fuel price €/l

Cable run m

Transfer power kW

Voltage V

System

Conductor

Max drop %

Array for 100% solar

-~~kWp~~

Clear-sky in plane-

Real in plane-

Direct sun window-

Max solar altitude-

Sun lost to terrain-

Reaching the arrayLost to the ridge

Balance

Installed array yields-

Daily balance-

Battery, nominal-

Generator, this month-

Fuel cost, this month-

Closing the gap with PV-

Cable

Design current-

Minimum section-

Next standard size-

Where the numbers come from

Solar position, angle of incidence and terrain blocking are computed for your coordinates and design day. Clear-sky irradiance uses the Hottel transmittance model with a mid-latitude winter atmosphere.

The cloud cover is yours to supply. Get the real monthly figure for your site from PVGIS and set the clear-sky index so the real figure matches. This page will not invent your weather.

Cable sections are sized on voltage drop alone. Current capacity, installation method and protection are separate checks, and none of this replaces the electrical code where you build.