Solar Savings Calculator (SG & MY)

ASEAN ENERGY SAVINGS SOLAR ENERGY SUSTAINABILITY

By RECATOOLS Editorial Last reviewed 2 Aug 2026

About this tool

See generation, bill savings and the year your panels pay for themselves

Solar panel savings and payback calculator — enter your system size in kWp and see annual generation, electricity-bill savings, the payback year on a 25-year curve, and the CO₂ avoided, with tropical peak-sun-hours and ASEAN tariffs for Singapore, Malaysia and beyond. Runs in your browser.

RT-SUS-004 · Sustainability & Environment

System size · 5 kWp

Region

System cost (installed)

Your tariff (optional)

/ kWh

Tariff inflation · 3%/yr

Used on site, not exported · 50%

Export credit (optional)

/ kWh

Inverter replacement, year 12

Payback period

—

Cumulative savings vs system cost (25 years)

How to Use the Solar Panel Calculator

Set your system size

Drag the kWp slider to the system you are considering. The tool uses your region’s peak-sun-hours to estimate annual generation.

Enter cost and tariff

Add the installed system cost and your electricity tariff (or pick a region preset) so savings are valued correctly.

Read the payback curve

The chart plots cumulative savings against the system cost; where they cross is your payback year, marked on the line.

Test assumptions

Adjust tariff inflation to see best- and worst-case payback, and read the lifetime savings and CO₂ avoided.

Solar Generation, Savings and Payback

Rooftop solar is one of the few household investments whose return you can estimate quite well in advance, because the physics is simple and the main variables are knowable. The starting point is your system size in kilowatts-peak — the panels’ rated output under standard sunlight. To turn that into real energy you multiply by the number of peak-sun-hours your location receives each day, by 365 days, and by a performance ratio of around 0.78 that quietly absorbs all the real-world losses: heat that makes panels slightly less efficient, dust on the glass, inverter conversion losses and resistance in the wiring. The tropics are well suited to solar: this calculator's presets run from 4.0 peak-sun-hours a day for Singapore to 4.8 for Thailand, so a modest system generates a substantial number of kilowatt-hours every year. Those presets are planning estimates, not measured site data — enter your own figure if you have one.

Those kilowatt-hours are worth money because each one you generate is one you do not buy from the grid. The calculator values your generation at your electricity tariff and projects it forward over the 25-year output warranty most quality panels carry. Two slow forces shape that projection: electricity tariffs tend to rise over time, which makes each future kilowatt-hour more valuable, while the panels themselves degrade by about half a percent a year, generating slightly less as they age. The first effect usually dominates the second, which is why the cumulative-savings curve bends upward over the decades. Plotting that curve against the upfront system cost reveals the moment the two meet — the payback point — after which every further year of generation is profit.

Seeing payback as a crossover on a chart, rather than a single number, makes the investment intuitive and lets you stress-test it. Nudge the tariff-inflation assumption and watch the payback year move; increase the system size and watch both the savings and the cost scale together. Alongside the money, the tool tracks the carbon you avoid: every grid kilowatt-hour you displace saves the emissions that would have been produced to generate it, and over 25 years that adds up to tonnes of CO₂, which the tool translates into relatable equivalents. None of this is a binding quote — your roof’s orientation and shading, the specific equipment, and your exact tariff scheme all matter — but it is a sound, transparent estimate computed entirely in your browser, and a good way to decide whether to take the next step and get a site survey.

Solar payback is not a single date but a crossing point — and rising tariffs pull that crossing steadily closer.

10 Facts About Rooftop Solar

Generation ≈ kWp × peak-sun-hours × 365 × performance ratio.

A peak sun hour = 1,000 W/m² of sunlight for an hour.

This calculator uses 4.0–4.8 peak-sun-hours across its ASEAN presets.

Performance ratio (~0.78) covers heat, dust and wiring losses.

Panels degrade only about 0.5% a year.

Most quality panels carry a 25-year output warranty.

Payback shortens as electricity tariffs rise.

Exported solar is usually credited below the import rate.

Heat actually reduces panel efficiency slightly.

This calculator runs in your browser — nothing is uploaded.

Frequently Asked Questions

The calculator multiplies your system size in kilowatts-peak (kWp) by the local peak-sun-hours per day, by 365 days, and by a performance ratio of about 0.78 that accounts for real-world losses from heat, dust, inverter inefficiency and wiring. The result is the kilowatt-hours your system should produce in a typical year.
A peak sun hour is one hour of sunlight at an intensity of 1,000 watts per square metre — the standard test condition for panels. A location with “4 peak sun hours” receives, over the whole day, the same total energy as four hours at that full intensity. The presets in this calculator run from 4.0 peak sun hours for Singapore to 4.8 for Thailand. They are planning estimates rather than measured site data, so if you have a figure for your own roof, enter it.
kWp, or kilowatts-peak, is the rated output of the panels under standard test conditions and is how solar systems are sized. A typical home system might be 3–10 kWp depending on roof space and consumption. Enter your planned size and the tool scales generation, savings and cost accordingly.
The tool builds a year-by-year curve of cumulative bill savings and finds the year it crosses your system cost — that crossover is the payback point, marked on the chart. Savings grow each year with assumed tariff inflation and shrink very slightly with panel degradation. Each kilowatt-hour is valued as a blend of the import tariff and your export credit, weighted by how much you use on site, and you can add an inverter replacement in year 12 so the curve pays for it. Every one of those factors is shown in the transparency panel beneath the result.
Because the savings are valued at whatever electricity costs in future. If tariffs rise, every kilowatt-hour your panels produce is worth more, so the payback arrives sooner and lifetime savings grow. The inflation slider lets you test optimistic and conservative assumptions.
Yes. It reduces output by about 0.5% per year, which is typical for modern panels, so the later years of the 25-year projection generate slightly less than the first. This is a small effect compared with tariff inflation but it is included for realism.
This matters more than almost anything else, and the answer changed recently. A kilowatt-hour you use as you generate it saves you the full import tariff; one you export earns whatever your scheme pays, and neither of our two main markets pays the import rate. In Singapore the Simplified Credit Treatment credits exports at the regulated tariff minus grid charges, so an exported unit is worth roughly 73 per cent of a self-consumed one. In Malaysia, net energy metering ended in June 2025 and Solar ATAP replaced it on 1 January 2026; domestic exports are credited at the Energy Charge component alone — about 27 sen against an import cost of about 44 sen, or roughly 61 per cent. Set the self-consumption slider to the share you actually use on site, and the tool blends the two rates for you.
Every kilowatt-hour your panels generate displaces a kilowatt-hour from the grid, avoiding the carbon that would have been emitted to produce it. The tool multiplies your generation by your grid’s carbon intensity and shows the annual and 25-year totals, translated into relatable equivalents.
No. They are a sound estimate for planning and comparison. Actual results depend on your roof orientation and shading, the specific equipment, local weather, installation quality and your real tariff and scheme. Use it to judge whether solar makes sense for you, then get a site-specific quote.
Completely free, with no account or usage limit. It runs entirely in your browser, collects no data, and works offline once the page has loaded.

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Solar Savings Calculator (SG & MY)