Most explanations of solar start with the quantum physics of photovoltaic cells. That's interesting but not useful. What actually matters for buyers is: what's in the system you're buying, what makes one system produce more than another, and where the failure points are.
This guide covers all three without oversimplifying and without drowning you in detail. By the end you should be able to read a solar quote and know what you're looking at.
From sunlight to electrons
A solar panel turns sunlight into direct current (DC) electricity. Here's the short version of how:
Each panel is made up of many individual solar cells — typically 60, 72, or 144 per panel. Each cell is a thin wafer of silicon that's been treated to create an electric field across its top and bottom surface. When light particles (photons) hit the silicon, they knock electrons loose. The electric field pushes those electrons in one direction — through a wire, out of the panel, through whatever's using the electricity, and back in the other side. That's the current.
The key practical fact: solar panels produce DC. Your home and grid run on AC. Converting between them is one of the two main jobs of the rest of the system.
The four hardware components
Every rooftop solar system has four essential parts. Everything else — batteries, monitoring, disconnects — sits on top of these.
1. Panels (the thing that makes electricity)
Panels are rated in watts peak (Wp) — their output under ideal test conditions. A 550 Wp panel at peak sun will generate about 550 watts of DC. Panels are wired together in "strings" so their voltages add up. A typical home system has 8–30 panels.
2. Inverter (DC to AC converter)
The inverter takes the DC coming out of the panels and converts it to the AC your home and grid run on. This is the second-most-important component after the panels themselves, and it's usually the first thing that needs replacing (typically year 10–12).
Three flavours exist:
- String inverter — one inverter for the whole array. Cheapest, most common, but a shaded panel can drag down the whole string.
- Microinverter — one inverter per panel. More expensive, but shading on one panel doesn't hurt the others. Good for complex roofs.
- Hybrid inverter — string inverter with built-in battery support. Spec this if there's any chance you'll want storage later.
3. Mounting system
Rails, clamps, and anchors that hold the panels to the roof. Looks boring on a spec sheet, causes most of the installation problems. Must be appropriate for your roof type (tile, metal, flat concrete), rated for your local wind loading, and installed without compromising roof waterproofing.
4. Balance of system (BOS)
Everything else that makes it work: DC and AC cabling, DC isolators, AC protection devices, earthing, the utility meter interface, and the monitoring connection. Quietly important. Cheap BOS is where cheap systems fail first.
Batteries, monitoring displays, EV charger integration, and power diverters all sit on top of the four essentials above. They're upgrades, not requirements.
The five numbers that decide yield
Two systems with identical hardware on identical-looking roofs can produce dramatically different amounts of electricity. Here's why. Any one of these five factors can swing output by 10–40%.
1. System size (kWp)
Just the sum of panel ratings. A 5 kWp system has panels that add up to 5 kilowatts peak. This is the headline number on every quote.
2. Peak sun hours at your location
This is the number of hours per day that effectively deliver full-strength sunlight for electricity-production purposes. Across Asia, it ranges from about 3.5 in consistently cloudy regions to 5.5+ in sunny tropical zones.
Rough formula: Annual kWh ≈ System kWp × Peak sun hours × 365 × 0.80
3. Orientation and tilt
South-facing (northern hemisphere) or north-facing (southern hemisphere) at a tilt close to your latitude captures the most annual energy. East- or west-facing panels lose 10–20%. The opposite-facing direction can lose 30%+.
4. Shading
Shading has outsized effects because solar cells are wired in series — like Christmas lights. A partial shadow on one cell can choke the current through the whole string. Modern bypass diodes and per-panel electronics mitigate this, but shading is still one of the biggest yield killers.
5. System losses
All the places electricity gets lost between panel and meter: inverter efficiency (~96–98%), cable losses (~2%), temperature derating (panels produce less when hot), dust accumulation, and natural panel degradation (~0.5%/year). Realistic systems lose 10–15% of nameplate output to these factors.
What can go wrong
Understanding failure modes is the fastest way to evaluate a quote. Here are the things that actually break solar systems, in rough order of frequency:
- Inverter failure (year 10–12). Expected. Should be in your 25-year cost model, not a surprise.
- Loose cabling / connectors. Usually a symptom of cheap installation or cheap BOS. Rare with a good partner.
- Water ingress at mounting points. Caused by poor flashing at roof penetrations. Why the installation team matters.
- Panel hot-spot failures. Manufacturing defect in one cell causes heat buildup. Tier-1 panels have very low rates. Caught by thermal imaging.
- Gradual output loss. Normal and expected: ~0.5% per year. Anything faster is a warranty claim.
- Physical damage. Fallen tree branches, severe hail, extreme weather. Rare but when it happens, insurance territory.
Panel warranties (25 years) get the headlines. But the inverter warranty (usually 10–12 years) is the one you'll actually use. When comparing quotes, pay particular attention to inverter terms — and whether labour for warranty replacement is covered.