title: How Solar Panels Work description: A plain-language explanation of how photovoltaic cells convert sunlight into electricity you can use at home. summary: A plain-language explanation of how photovoltaic cells convert sunlight into electricity you can use at home. category: solar difficulty: Intro updated: 2026-02-09 tags: ["solar", "technology", "basics", "photovoltaic"] relatedTools: ["/tools/solar-sizing", "/tools/solar-roi"] faqs:

• question: Do solar panels work on cloudy days? answer: Yes. Solar panels still generate electricity on cloudy days, though at reduced output — typically 10–25% of their rated capacity depending on cloud thickness. They do not need direct sunlight to function.
• question: How long do solar panels last? answer: Most modern solar panels are warrantied for 25–30 years and continue producing electricity well beyond that. They degrade slowly, losing roughly 0.3–0.5% efficiency per year.
• question: Do solar panels work in cold climates? answer: Absolutely. Solar panels are actually slightly more efficient in cooler temperatures. Production depends on sunlight hours, not temperature. Germany, with a climate similar to Alaska, is one of the world's top solar producers.
• question: How much roof space do I need for solar? answer: A typical residential system (6–8 kW) needs roughly 300–500 square feet of unshaded roof space. Each panel is about 18 square feet and produces 350–400 watts.
• question: What happens to solar panels at night? answer: Solar panels do not generate electricity at night. Grid-tied systems draw power from the utility grid after dark. If you have a battery, stored energy covers nighttime usage.

How Solar Panels Work

Solar panels convert sunlight directly into electricity through the photovoltaic (PV) effect — a process discovered in 1839 and commercialized in the 1950s. Today, it powers millions of American homes.

The Photovoltaic Effect

At the heart of every solar panel are photovoltaic cells, typically made from silicon — the same material in computer chips.

Here's what happens when sunlight hits a solar cell:

1. Photons arrive — Sunlight is made up of tiny packets of energy called photons
2. Electrons break free — When photons strike the silicon cell, they knock electrons loose from their atoms
3. Electric field directs flow — The cell has two layers of silicon (positive and negative) that create an electric field, pushing freed electrons in one direction
4. Current flows — This directed movement of electrons creates direct current (DC) electricity

A single solar cell produces about 0.5 volts. Multiple cells are wired together into a module (what we call a "solar panel"), and multiple modules form an array (your rooftop system).

From Panel to Outlet

The electricity from your panels can't power your home directly — it needs a few more steps:

• DC electricity leaves the panels
• An inverter converts DC to alternating current (AC), which is what your outlets and appliances use
• AC power flows to your electrical panel (breaker box)
• Your home uses what it needs; excess goes to the grid (with net metering, you get credit)

Types of Solar Panels

| Type | Efficiency | Cost | Best For | |------|-----------|------|----------| | Monocrystalline | 19–23% | Higher | Limited roof space; maximum output | | Polycrystalline | 15–17% | Lower | Budget-conscious; ample roof space | | Thin-film | 10–13% | Lowest | Commercial roofs; flexible surfaces |

Most residential installations today use monocrystalline panels because their higher efficiency means fewer panels for the same output.

Key Performance Factors

Sunlight hours — Your location determines how many "peak sun hours" you get per day. Arizona averages 6–7; the Pacific Northwest averages 3–4.

Roof orientation — South-facing roofs produce the most energy in the Northern Hemisphere. East/west-facing roofs produce about 15–20% less.

Shading — Even partial shading on one panel can disproportionately reduce output. Modern systems use microinverters or power optimizers to minimize this.

Temperature — Panels lose about 0.3–0.5% efficiency per degree Celsius above 25°C (77°F). Hot climates see slightly lower per-panel output than their sun hours suggest.

Panel age — Modern panels degrade at 0.3–0.5% per year. After 25 years, they still produce 85–90% of their original output.

What This Means for You

Understanding how solar works helps you make better decisions:

• More panels isn't always better — system sizing should match your actual electricity usage
• Inverter choice matters — microinverters cost more but perform better with shade
• Location determines everything — your state's sun hours and electricity rates drive your ROI

Use our Solar Sizing Calculator to see what system size fits your home, or start with the Solar ROI Calculator to check if the numbers make sense for your situation.