Whether you are building a phone charger or planning a roof full of panels, the fundamentals are the same. Here is everything you need to know.
Solar panels contain photovoltaic (PV) cells that convert sunlight directly into electricity. When photons hit the silicon cells, they knock electrons loose, creating a flow of direct current (DC) electricity. The more sunlight that hits the panel, the more electricity it produces. Modern monocrystalline panels convert 20–25% of sunlight into usable electricity.
Every solar system, from a phone charger to a whole-house installation, uses the same four building blocks:
Monocrystalline panels are the current standard — highest efficiency (20–25%), longest lifespan (25+ years), and steadily dropping prices. Polycrystalline panels are slightly cheaper but less efficient. Thin-film / CIGS panels are flexible and ultralight but lower efficiency — best for curved surfaces like van roofs. For most builds on this site, monocrystalline is the right choice.
Sits between the solar panel and the battery. Its job is to regulate the voltage and current flowing into the battery to prevent overcharging. Two types: PWM (cheaper, simpler, fine for small systems) and MPPT (15–20% more efficient, worth it for systems over 200W). Think of it as the brain of your solar system.
LiFePO4 (Lithium Iron Phosphate) is the gold standard in 2026. It lasts 3,000–5,000 charge cycles, is safe (no thermal runaway risk), lightweight, and holds charge for months in storage. Older lead-acid batteries are cheaper upfront but heavier, shorter-lived (500 cycles), and need maintenance. For any new build, go LiFePO4.
Converts 12V/24V/48V DC power from the battery into 120V AC — the same kind of power from your wall outlets. Pure sine wave inverters produce clean power safe for all electronics including CPAP machines, laptops, and sensitive instruments. Modified sine wave inverters are cheaper but can damage some devices. Always go pure sine wave.
The formula is simple:
Array Size (W) = Daily Energy Need (Wh) ÷ Sun Hours ÷ 0.85 (system losses)
Example: You need 1,000Wh/day (a small fridge + lights + phone charging). Your location gets 5 sun hours per day. 1,000 ÷ 5 ÷ 0.85 = 235W of solar panels. Round up to 300W for cloudy-day margin.
For battery sizing: Battery Capacity (Ah) = Daily Wh ÷ Battery Voltage ÷ Allowed Depth of Discharge. For LiFePO4, you can safely discharge to 80–90% of capacity. For a 1,000Wh daily need on a 12V system: 1,000 ÷ 12 ÷ 0.85 = ~98Ah. A 100Ah LiFePO4 battery covers it.
Watts = Volts × Amps. That is the only formula you really need. Watts measure total power (how much work it does). Volts measure electrical pressure (think water pressure). Amps measure flow (think water flow rate). A 100W panel at 12V produces about 8.3 amps. A 100Ah battery at 12V stores 1,200Wh of energy.
Series: Connects panels positive-to-negative. Voltage adds up, amps stay the same. Use when you need higher voltage for MPPT controllers or long cable runs. Parallel: Connects all positives together, all negatives together. Amps add up, voltage stays the same. Use for 12V systems or when panels might be partially shaded (one shaded panel does not drag down the others).
Now that you know the basics, pick a project and get started: