Solar Basics: How Solar Panels Work in Malaysia

How a Solar System Actually Works

A rooftop solar system does one job: it turns sunlight into electricity your building can use straight away. Four things happen, in order.

1. Sunlight hits the panels. Each panel is made of silicon cells. When light strikes them, electrons move — the photovoltaic effect. No moving parts, no noise, no fuel.
2. The panels produce DC electricity. Direct current, the same kind a battery produces. Your appliances cannot use it in that form.
3. The inverter converts DC to AC. Alternating current at 240V, the same as what comes from TNB. This is the only part of the system doing real work, which is also why it is the part that wears out first.
4. The electricity flows to your loads first. Your aircond, fridge, lights and sockets draw from the solar before they draw from the grid. Only what you cannot use goes anywhere else.

That last point is where most of the savings come from, and it is the part people misunderstand most often. Solar is worth the most when you use the power as it is produced. Exporting is the fallback, not the goal.

The Five Parts of a Rooftop System

A system without a battery is called grid-tied or on-grid. It is the most common setup in Malaysia and the cheapest per kilowatt.

How Much Electricity a System Produces in Malaysia

Malaysia averages roughly 4 to 4.5 peak sun hours a day. A peak sun hour is one hour of sunlight at 1,000 watts per square metre — the same intensity panels are rated at. So a panel rated 1 kW sitting under 4.5 peak sun hours would, in perfect conditions, make 4.5 kWh in a day.

Perfect conditions do not exist on a roof. After inverter conversion, cable losses, heat and dust, a realistic figure in Malaysia is 3.5 to 4 kWh per kWp per day, or roughly 1,300 to 1,450 kWh per kWp per year.

Worked example. A 6 kWp system on a terrace house roof:

• 6 kWp × 3.8 kWh/kWp/day = about 22.8 kWh a day
• Over a month: roughly 680 kWh
• A household using 900 kWh a month would cover about three quarters of its consumption — but only the portion actually consumed while the sun is up counts as direct savings

This is why a house where somebody is home during the day, or a factory running weekday shifts, gets more out of solar than a house that is empty from 8am to 7pm.

What Changes Your Output

Two identical systems on two roofs in the same town can differ by 20% or more. These are the reasons:

• Orientation. In Malaysia, panels facing roughly south or north perform similarly; east and west roofs lose a little but spread production across the morning and afternoon, which can suit some usage patterns better.
• Tilt. A shallow tilt of 10–15° is typical here. Too flat and dirt does not wash off in the rain.
• Shading. The one that hurts most. A single shaded panel can drag down a whole string. Trees, a neighbour’s upper floor, a water tank, an antenna — all matter, and all change through the day.
• Heat. Panels lose output as they get hotter, typically around 0.3% for every degree above 25°C. Malaysian roof surfaces regularly hit 55–65°C at midday, which is why a panel rated 600W rarely delivers 600W here. Air gap under the panels helps.
• Dust and haze. Ordinary rain handles most of it. Haze season and long dry spells are when output visibly dips.
• Monsoon. Production falls during the wetter months and rises in the drier ones. Judge a system on a full year, not on one rainy fortnight.

What Solar Does Not Do

Worth being blunt about, because these three surprise people after installation:

• It does not keep your lights on during a blackout. A standard grid-tied system shuts down the moment the grid goes out. That is a safety requirement called anti-islanding, so that your system does not push power into lines that technicians may be working on. Backup during an outage requires a battery and a hybrid inverter.
• It does not produce anything at night. Evening consumption still comes from the grid unless you have storage.
• It does not zero your bill. There are fixed charges, and there is night-time and rainy-day consumption. A well-sized residential system usually cuts a bill substantially rather than eliminating it.

On-Grid, Hybrid or Off-Grid

If your building already has a reliable TNB supply, off-grid is almost never the right answer. It costs more and gives you less.

Where Your Extra Energy Goes

Malaysia’s Net Energy Metering (NEM) scheme closed to new registrations on 30 June 2025. Its replacement, Solar ATAP, took effect on 1 January 2026 and governs how excess energy is treated for new residential systems, alongside the SuRIA Home cash rebate.

Many guides still refer to “NEM 3.0”. If you are installing now, that scheme no longer accepts new applications — the terms that apply to you are Solar ATAP’s. Read the current position in Solar Incentives Malaysia 2026, and for companies, the GITA tax allowance.

How to Read a Solar Quotation

Quotations use a handful of terms that look interchangeable but are not. Getting these straight makes comparing two quotes far easier.

• kWp (kilowatt-peak) is the size of the panel array under standard test conditions. This is the number that defines your system size — a “6 kWp system” has 6,000 watts of panels.
• kW of the inverter is a separate number and is often slightly smaller than the array. A 6 kWp array on a 5 kW inverter is normal, not a mistake. Panels rarely hit their rated output in Malaysian heat, so a modest amount of oversizing captures more energy across the day.
• Panel wattage (say 580W or 620W per panel) only tells you how many panels you need for a given kWp. A higher wattage panel is not automatically better; it is usually just physically larger.
• Efficiency is how much of the sunlight hitting a panel becomes electricity, typically 20–23% for current residential panels. It matters when roof space is tight. If you have plenty of roof, a cheaper panel at lower efficiency can be the better buy.
• kWh is energy produced or consumed — what you are billed on. kWp is capacity, kWh is output. Two different things.

Ask for the estimated annual kWh, not just the system size. Two installers quoting the same 6 kWp can project different yields depending on the panel, inverter and layout they propose — and that projection is what your savings estimate rests on.

How Long Panels Last, and What Degradation Means

Solar panels do not stop working at a fixed date. They slowly produce less.

Current panels typically degrade around 0.4% to 0.55% a year after an initial first-year drop. At that rate, a panel still produces roughly 85–90% of its original output in year 25. That is why manufacturers can offer a 25-year performance warranty — it guarantees an output percentage at year 25, not that nothing changes.

Two warranties appear on most quotations and they are not the same thing:

The workmanship warranty is the one people skip over, and it is the one that matters if a mounting bracket leaks in three years. A manufacturer warranty is only useful if the company that installed your system is still around to process the claim.

What Maintenance Actually Involves

Less than most people expect, but not nothing.

• Cleaning. Malaysian rain does most of the work on a tilted array. A wash once or twice a year is usually enough, more if you are near a construction site, a palm oil mill, or a busy road.
• Monitoring. Every modern inverter reports daily production to an app. Checking it monthly is the single most useful habit — a failing string or a shaded panel shows up as a dip long before you would notice it on your bill.
• Inverter check. Fans and capacitors are the wear items. An inspection every couple of years is reasonable.
• Roof and mounting. Worth inspecting after unusually heavy storms, and worth checking that no new shade has grown into the array — trees do not stay the same size.

Budget for one inverter replacement somewhere between year 10 and 15. A system quoted with a 25-year payback story that never mentions the inverter replacement is not being straight with you.

Solar and Your TNB Bill

Solar reduces the energy portion of your bill, which is the largest part for most households and businesses but not the whole of it. Your bill also carries capacity, network and retail components, plus adjustments such as AFA (previously ICPT), and service tax above certain usage levels.

Because Malaysia’s domestic tariff is tiered, the savings are strongest for households in the higher usage bands — every kWh solar removes is taken off the most expensive block first. A house consuming 1,400 kWh a month saves more per kWh generated than one consuming 400 kWh.

For commercial and industrial accounts, there is a second effect: Maximum Demand charges. Solar shaving your afternoon peak can reduce the MD component as well as the energy component, and on some tariffs that is the larger saving of the two. Read how the RP4 tariff is structured and how Time-of-Use periods work before sizing a commercial system.

How to Tell If Your Roof Is a Reasonable Fit

Before anyone quotes you, you can sanity-check most of it yourself:

• Your bill. Below roughly RM200 a month, the payback stretches out and the case gets thin. The higher the bill, the stronger the case.
• Daytime usage. The more of your consumption happens between 9am and 5pm, the better solar performs for you.
• Usable roof area. Rough guide: about 5 to 6 square metres per kWp of panels, on a surface that is not shaded for most of the day.
• Roof condition and age. Panels last 25 years. If the roof needs replacing within five, deal with the roof first.
• Ownership. The TNB account and the property should be in a position where you can commit for the long term.

None of that replaces a site survey, but it will tell you quickly whether a quotation is worth asking for. To put numbers to it, use the TNB bill calculator and read how the TNB tariff is structured.