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How solar works

Follow the energy.

From light on a roof to electricity in a kitchen: six steps, in plain language. Follow the golden line down the page — it traces the path electricity takes through a home solar system.

Start following See the whole system
Close view of solar panel rows under a bright sky

Energy path

Input
Daylight
Generated
Direct current
Converted
Alternating current
Used
Home first, then grid
Residential solar context Photo: Chirayu Trivedi on Unsplash

01 Sunpath

Sun → module → DC → inverter → home ↔ grid.

Each station below is one step on the path. The illustrations are simplified and conceptual; the text alongside each one says the same thing in words.

  1. 01 Sun

    Daylight reaches the roof

    Solar modules respond to light. Direct sunshine produces the most, but diffuse light on a bright overcast day still contributes. How much reaches a roof depends on location, season, time of day, orientation, pitch and shading.

    Light is the input — and it varies.

  2. 02 Solar module

    Cells behind glass

    A module is a framed sheet of photovoltaic cells behind toughened glass. Several modules laid across a roof plane form the array. Their size, rated output and technology differ between products.

    Modules are the visible part of the system.

  3. 03 DC generation

    Light becomes direct current

    When light reaches the cells, they produce direct current (DC) — electricity that flows in one direction. Modules are connected together, and their DC output travels by cable towards the inverter.

    DC is not what household circuits use.

  4. 04 Inverter

    DC is converted to AC

    The inverter converts DC into alternating current (AC), the form a home’s circuits and appliances run on. It is usually also where the system’s performance can be monitored.

    The inverter connects generation to the home.

  5. 05 Home

    The home uses it first

    Solar electricity flows into the household circuits through the consumer unit. Whatever is running at that moment — a fridge, a washing machine, a laptop — uses it before anything is drawn from the grid.

    Using it as it is generated is called self-consumption.

  6. 06 Grid

    The grid works in both directions

    When the home needs more than the array produces, electricity is imported from the grid as usual. When the array produces more than the home needs, the surplus can flow out — and, where suitable metering and an export arrangement exist, be measured as export.

    Import and export: the grid sits alongside.

02 How solar moves

From sunlight to electricity the home can use.

Light becomes direct current in the modules, the inverter turns it into the alternating current a home runs on, and the home uses what it needs. The grid sits alongside, in both directions.
From sunlight to electricity the home can use Sunlight reaches the solar modules on the roof, which generate direct current. The inverter converts it to alternating current for the home. The home uses what it needs; where an export arrangement exists, surplus can pass to the grid, and the grid supplies the home when solar generation is not enough. 01 SUNLIGHT 02 PV MODULES 03 INVERTER 04 HOME 05 GRID DC GENERATION DC → AC USED FIRST IMPORT ↔ EXPORT EXPORT* IMPORT From sunlight to electricity the home can use Sunlight reaches the solar modules on the roof, which generate direct current. The inverter converts it to alternating current for the home. The home uses what it needs; where an export arrangement exists, surplus can pass to the grid, and the grid supplies the home when solar generation is not enough. 01 SUNLIGHT 02 PV MODULES DC GENERATION 03 INVERTER DC → AC 04 HOME USED FIRST 05 GRID IMPORT ↔ EXPORT*

Diagram key

  1. 01 Sunlight Daylight reaches the roof. Direct sun produces most, but modules also respond to diffuse light.
  2. 02 PV modules Photovoltaic cells generate direct current (DC) when light reaches them.
  3. 03 Inverter Converts DC into alternating current (AC) suitable for household circuits.
  4. 04 Home Appliances running at that moment use solar electricity first.
  5. 05 Grid Supplies the home when solar is not enough. Surplus may be exported where an arrangement exists (*).

* Export depends on suitable metering and an export arrangement with a participating supplier. Follow the energy in detail

03 Variation

Why the same system performs differently.

Every step on the path depends on conditions. The amount of light depends on the season and the weather; the share used at home depends on when the household is in; what reaches the grid depends on both.

That is why generation is modelled from assumptions — orientation, pitch, shading, equipment, location and losses — rather than promised.

How generation estimates work

Sunlight falling across a pitched roof
Residential solar context Photo: Giorgio Trovato on Unsplash

04 Vocabulary

Six terms worth knowing.

These come up in almost every solar conversation and proposal. Knowing them makes a proposal easier to read.

  1. DC

    Direct current

    Electricity that flows in one direction. Solar cells produce DC.

  2. AC

    Alternating current

    Electricity that changes direction many times a second. Household circuits use AC.

  3. kWp

    Kilowatt peak

    A system’s rated output under standard test conditions — a way to compare sizes, not a prediction of output.

  4. kWh

    Kilowatt hour

    A unit of energy. Electricity use, generation estimates and bills are all measured in kWh.

  5. SELF-CONSUMPTION

    Self-consumption

    Solar electricity used in the home at the moment it is generated.

  6. EXPORT

    Export

    Surplus electricity leaving the home for the grid, measured where suitable metering exists.

Questions

How solar works: questions

Do solar panels work on cloudy days?

Yes, modules respond to diffuse daylight as well as direct sun, but output is lower when it is overcast. That variability is why generation is always described as an estimate.

Do solar panels work at night?

No. Without light, the modules do not generate. At night a home draws its electricity from the grid as usual.

Why does a system need an inverter?

Solar cells produce direct current (DC), but household circuits and appliances use alternating current (AC). The inverter converts one into the other. See inverters and monitoring.

What happens to electricity the home does not use?

It flows to the grid. Where suitable metering and an export arrangement exist, it can be measured as export. Customers interested in export payments should review current Smart Export Guarantee requirements and participating supplier terms. See solar export.

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