Singapore Solar Earns S$3,100 a Year Through Every Monsoon

Every homeowner who has looked at solar in Singapore has asked the same question: what about the rain? Your terrace house sits under a sky that delivers two monsoon seasons a year, afternoon thunderstorms across June through September, and grey overcast mornings that look like nothing is happening. Here is the insight most people miss: your panels are generating anyway, and by the end of this article you will see exactly how much every monsoon month is already worth in your payback number.

Singapore Gets More Usable Solar Than Most Cities on Earth

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Singapore sits just one degree north of the equator. That geography delivers 1,580 kWh/m²/year of solar irradiance, one of the highest figures among major city-states anywhere, as confirmed by IEA solar data. London averages roughly 1,000 kWh/m²/year, and the UK solar market is enormous.

The standard planning figure for Singapore is 4.33 average peak sun hours per day. That number already accounts for every cloudy afternoon, every monsoon month, every grey January morning. It is the annual average across all 365 days, not a cherry-picked sunny day figure.

Solar installers and the Energy Market Authority both use this figure when modelling system output. When your installer quotes you an annual generation estimate, the rain is already priced in.

What Overcast Skies Actually Do to Your Output

Panels generate electricity from light, not heat and not direct sunshine. On an overcast day, diffuse light still reaches the panel surface from every angle across the sky. That diffuse light produces real electricity.

A well-installed Singapore system on a heavily overcast day typically generates 30-50% of its clear-sky peak. On a day with partial cloud cover, you are often at 60-80%. Output never drops to zero unless someone physically covers every panel.

The psychological trap is treating rainy days as lost days. A 10kWp system generating at 35% of peak on a monsoon afternoon is still producing roughly 15 kWh that day. At the current regulated tariff of S$0.3478/kWh (inclusive of 9% GST, SP Group Q3 2026), that single overcast day saves or earns you over S$5. Across a monsoon month, those days stack up into real money.

Singapore's Two Monsoon Seasons and What They Mean for Your Roof

Singapore has two distinct monsoon seasons. The Northeast Monsoon runs from roughly November through January, bringing steady rain and more persistent cloud cover. The Southwest Monsoon covers June through September, with heavy afternoon thunderstorms that clear quickly.

Between those windows, February through May and parts of October typically deliver Singapore's strongest solar months, with clearer mornings and lower humidity. The variation between Singapore's best and worst solar months is far smaller than anywhere with true seasons.

Here is a Sunnify estimate of monthly generation for a 10kWp terrace house system in Singapore:

Month	Est. Generation (kWh)	Conditions
January	780	NE Monsoon peak
February	920	Transition, improving
March	1,010	Strong solar month
April	1,020	Strong solar month
May	1,000	Pre-SW Monsoon
June	890	SW Monsoon starts
July	870	SW Monsoon
August	860	SW Monsoon
September	870	SW Monsoon tail
October	960	Transition, strong
November	820	NE Monsoon begins
December	800	NE Monsoon peak
Annual total	11,000	Sunnify estimate

Note: These are Sunnify estimates based on Singapore's 4.33 peak sun hour average and a 10kWp system with standard 70% yield factor. Your actual figures depend on roof pitch, orientation, and shading. Confirm with your installer or EMA's solar resource data.

The difference between Singapore's best month (April, ~1,020 kWh) and worst month (January, ~780 kWh) is roughly 24%. Compare that to Germany, where the best-to-worst month swing exceeds 400%. Singapore's solar profile is remarkably flat precisely because of the equatorial position.

Rain Does Something Else: It Cleans Your Panels for Free

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Panel soiling, dust and grime settling on the glass surface, causes output losses of 2-3% in dry climates. Singapore's frequent rain acts as a continuous free wash cycle, keeping your panels cleaner than those in Dubai, Perth, or California, where soiling is a real maintenance cost.

Most Singapore installers do not include a professional cleaning schedule in their maintenance plans precisely because the rain handles it. That is a hidden financial benefit of exactly the weather that worries you most.

The Annual Average Is the Only Number That Pays Your System Off

Payback calculations do not care about January. They care about the 12-month total generation that your 10kWp system produces across all conditions, which lands at approximately 11,000 kWh/year (Sunnify estimate).

At a self-consumption rate of 25%, you consume roughly 2,750 kWh directly, saving S$957/year at the current tariff of S$0.3478/kWh. The remaining 75%, about 8,250 kWh, exports to the grid at the Simplified Credit Treatment rate of S$0.2581/kWh, adding another S$2,129/year and bringing your combined annual return to approximately S$3,086/year.

A 10kWp system on a Singapore terrace house costs approximately S$10,000-S$16,000 installed (Sunnify estimate based on current market rates of S$1,000-S$1,600/kWp). At the mid-range of S$13,000, payback sits at roughly 4.2 years. The rainy months are fully included in that calculation already.

Over 25 years, your system accumulates approximately S$77,000 in savings and export income at current tariff levels, before accounting for any future tariff increases. See the full Singapore ROI breakdown if you want to run the 25-year picture in detail.

Stop Optimising for the Worst Day. Start Counting the Best 198.

The rainy days are already in your payback number. The question is whether you keep paying the grid while they pass.

Singapore averages roughly 167 rain days per year. That means roughly 198 days with limited or no significant rainfall, and most of those deliver strong solar output. Focusing your decision on the 167 bad days while ignoring the 198 good days is the wrong frame entirely.

Every month that passes without solar on your terrace house is a permanent loss, not a delay you can recover. You keep paying S$0.3478/kWh for every unit your panels would have generated for free, and that money does not come back when you eventually install.

When you run your numbers, look at the annual generation figure, not the worst-month figure. The annual number is the one that your installer underwrites, the one that drives your payback period, and the one that PV Tech's performance research on equatorial locations consistently validates. When you are ready to see what your specific roof generates across all twelve months, run your Sunnify solar estimate and check the monthly breakdown tab.

Your Move: Lock In the Number the Rain Cannot Touch

When you install on your terrace house this year, next January's monsoon is already paid for in your payback model. Picture yourself in February 2028, checking your generation dashboard and watching your best solar months stack savings while your neighbours debate whether the rain is a problem.

The 4.33 peak sun hours is your floor, not your ceiling. Every season delivers above it or at it, never below the annual average that your payback is built on. Run your Sunnify solar estimate, enter your terrace house details, and see the monthly generation profile that shows you exactly what each monsoon season is worth in dollars, not worry.

Do solar panels work during Singapore's monsoon season?

Yes. Panels generate electricity from diffuse light, not direct sunshine, so overcast monsoon days still produce 30-50% of peak output. Singapore's annual average of 4.33 peak sun hours already accounts for both the Northeast Monsoon (November to January) and the Southwest Monsoon (June to September). See EMA's solar resource data for the underlying irradiance figures.

How much less electricity do solar panels generate on a rainy day in Singapore?

On a heavily overcast or rainy day, a well-installed Singapore system typically generates 30-50% of its clear-sky peak output. Partial cloud cover days often deliver 60-80%. Output never reaches zero under normal cloud conditions. The more relevant figure is the annual total: a 10kWp terrace house system produces approximately 11,000 kWh/year across all weather, which is the figure that drives your payback calculation. Check your roof's specific generation potential here.