Where the power comes from

Arrays follow the sun you see in the game: they start at dawn, peak at the game's noon and stop at dusk. How much they make depends on the season, the sky and the glass.

A day of sun

On 9 July the sun is up from 07:03 to 21:35 and peaks at 14:19. On 21 December it is up from 07:50 to 17:11 and peaks at 12:30. Summer days are longer and the sun climbs higher, so a July day makes far more than a December day. After the game's dusk the sky stays bright for a while, but the panels are already done.

What cuts the output

Clouds: a fully overcast sky costs about four fifths, and rain on top a little more. Fog on its own costs less.
Snow: snow on the glass blocks light; buried, a panel makes nothing. Use Off-Grid › Sweep the snow off.
Dust: dirty glass loses up to 40%. Rain washes it, or use Off-Grid › Clean the panels with a rag and water.
Damage: a cracked array still makes at least a quarter. Off-Grid › Repair the frame with scrap electronics, screws and a screwdriver.
Heat: hot cells lose 0.3 to 0.5% per degree above 25 C, depending on the grade.
A roof overhead: an array indoors or under a roof makes nothing. Its Info card says Sky: under a roof.

Ground frame or roof panel?

Ground frame, 32°: aimed at the winter sun and sheds snow. Face it south; north costs you most.
Roof panel, 6°: lies almost flat. It wins July, loses January, and holds snow: a thaw clears it at under a third of a frame's pace, so climb up and sweep it.

Realistic Mode

A sandbox option, off by default: Sandbox › Off-Grid › Realistic Mode (1993 panels). Panels make what panels made in 1993: three modules of about 50 W to a frame, so a standard frame gives about 140 W in full sun instead of about 570 W. Makeshift frames make about half that, premium frames a little more. Everything that shows panels, and the almanac, follows the setting at once. It also makes backup generators burn what a real gasoline generator burns. On a server an admin can switch it mid-game; in singleplayer it is set when you create the world. Figures by Alwar, from the Suggestions board. See Grades compared for every grade.

Numbers

An MPPT controller harvests 10% more from the same panels.
Controller efficiency: 93% basic, 96.5% MPPT.
The almanac forecasts your daily energy for the next 29 days.