Solar Savings Calculator (SG & MY)

Frequently Asked Questions

• How is annual solar generation calculated?+
  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.
• What is a peak sun hour?+
  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. The usual free reference, the World Bank and ESMAP’s Global Solar Atlas, puts the long-term average nearer 4.4 kWh/m² a day over Singapore and 4.9 over Bangkok, so these presets are the conservative end of the published range. If you have a figure for your own roof — from an installer or a monitoring portal — enter it instead.
• What is kWp?+
  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.
• How is the payback period worked out?+
  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.
• Why does tariff inflation matter so much?+
  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.
• Does the calculator account for panel degradation?+
  Yes. It reduces output by 0.5% a year, the median long-term degradation rate found by Jordan and Kurtz in their 2013 review of nearly 2,000 published field measurements (Progress in Photovoltaics 21(1):12-29), so the later years of the 25-year projection generate slightly less than the first. Hot, humid climates tend to sit above the median, so treat 0.5% as a central estimate rather than a floor. It is a small effect beside tariff inflation, but it is in the arithmetic.
• What about net metering or feed-in tariffs?+
  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.
• How much CO₂ does solar avoid?+
  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.
• Are these numbers a guaranteed quote?+
  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.
• What is the performance ratio, and why 0.78?+
  The performance ratio (PR), defined in IEC 61724-1, is the energy a system actually delivers divided by what its nameplate rating would deliver under the sunlight it received — every real-world loss in one number: module temperature, soiling, wiring, mismatch and inverter conversion. Well-built systems in temperate climates commonly report PR values around 0.80–0.85; in the tropics module temperatures run higher, which pushes PR down. The 0.78 used here is a planning default at the conservative end of that range, not a measurement of any particular roof, and the peak-sun-hour presets are likewise planning figures — enter your own PSH and PR if an installer or a monitoring portal has given you measured values.