A solar system is simple at heart: panels make electricity from light, an inverter makes it usable, and the grid or a battery handles the times when the sun is not shining. Here is each piece in order.
From sunlight to electricity
A solar cell is a thin wafer of silicon treated so that one side has extra electrons and the other has room for them. When light strikes the cell, its energy knocks electrons loose. The built in electric field pushes them toward metal contacts, and that flow of electrons is direct current (DC) electricity. This is called the photovoltaic effect.
One cell makes only about half a volt, so a panel wires 54 to 144 cells (or half cells) together behind tempered glass. Panels are then joined into strings and arrays to reach a useful voltage and power.
The parts of a system
- Panels (modules): make DC power. Most residential panels today are rated 400 to 480 watts.
- Inverter: turns DC into the alternating current (AC) your home uses. It can be one central box, a small microinverter under each panel, or a hybrid unit that also runs a battery. See Inverters.
- Racking: the rails and mounts that hold panels to the roof or ground.
- Disconnects and breakers: safety switches required by electrical codes.
- Meter: the utility usually installs a bidirectional meter that counts power in both directions.
- Monitoring: an app or web portal that shows production and use.
- Battery (optional): stores energy for the evening or for outages. See Batteries.
Three kinds of systems
| Type | How it works | Works in a blackout? | Best for |
|---|---|---|---|
| Grid tied | Uses solar first, draws from the grid when needed and exports extra. | No. It shuts off for line worker safety. | Lowest cost per kWh where grids are reliable. |
| Grid tied with battery (hybrid) | Same as grid tied, plus a battery for evenings and outages. | Yes, for the circuits you choose. | Frequent outages, time of use rates, low export credits. |
| Off grid | Panels, batteries and usually a generator, with no utility connection. | There is no grid to lose. | Remote homes, farms, islands and villages. |
Power versus energy
Power, in kilowatts (kW), is how fast electricity flows at a moment. Energy, in kilowatt hours (kWh), is power over time. A 6 kW system in full sun for 5 hours makes about 30 kWh before losses. Your bill charges for energy, so kWh is the number to watch.
What decides how much a system produces
- Sunshine: measured as peak sun hours. The Atacama Desert gets far more than Vancouver.
- Direction and tilt: face the equator (south in the Northern Hemisphere, north in the Southern) with a tilt near your latitude for the most yearly energy. East and west roofs still work well.
- Shade: even a chimney shadow can cut output. Optimizers and microinverters limit the damage.
- Heat: panels lose a little output as they get hotter, so airflow matters in tropical climates.
- Dust and snow: soiling can cost several percent in dry regions; rain usually cleans panels.
What happens at night and on cloudy days
Panels still produce on cloudy days, often 10 to 25 percent of normal. At night they produce nothing. A grid tied home simply buys power from the utility at night; how much solar saves depends on how your utility credits daytime exports. That is why net metering and net billing rules matter so much.
How long it lasts
Quality panels carry 25 to 30 year warranties and typically lose around half a percent of output per year. String inverters usually last 10 to 15 years; microinverters often carry 25 year warranties. Batteries last about 10 to 15 years depending on chemistry and use.
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