Malaysia home solar calculator: estimate panel capacity from billed kWh
Decision details
Fits if: Landed residential homeowners in Peninsular Malaysia with monthly TNB bills seeking an early system size estimate before installer consultations.
Main drawback: A TNB bill alone cannot fix the final system size or real savings — roof condition, shading and daytime usage still need an on-site installer assessment.
Compare: Billed monthly kWh consumption, statement billing cycle days, gross generation target percentage, and estimated daily site yield.
Estimate home solar size from billed TNB kWh
Enter billed kWh, billing days, a gross generation target and a site-specific yield assumption to estimate kWp.
Enter the kWh and billing days shown on your bill. The site-specific yield in kWh/kWp/day must come from a site assessment or quote; there is no default. Gross generation is different from energy used on site or export credits.
In this guide
Use this T10 solar calculator for one specific job: turn TNB bill kWh and billing days, a gross-generation target and an assumed site yield into a preliminary solar-panel capacity in DC kWp. It does not calculate ROI or bill savings, set the final system design, assess your roof or produce an installer quotation. For comparing quote and savings assumptions, use the solar worksheet guide; for home, business and proposal scenarios, use the solar hub and scenario calculator. Confirm site design and price with a provider before committing to an installation.
How much solar kWp capacity does your TNB bill actually require?
This calculator helps residential homeowners in Peninsular Malaysia estimate early system sizing: what solar panel capacity (in kWp) corresponds to your actual electricity usage on a TNB bill?
This tool uses billed energy in kWh and billing days rather than the ringgit total. The cited RP4 energy + capacity + network references are RM0.4443/kWh for the lower-usage account category and RM0.5443/kWh for the higher-usage category, separated at 1,500 kWh/month [source] [source] [source]. These composite references exclude AFA and other bill adjustments; they are not sequential marginal blocks or a complete bill formula. The AFA gate is temporarily 800 kWh/month through 31 December 2026 and reverts to the 600 kWh baseline from 1 January 2027 — never read a single unqualified gate number [source] [source]. The September 2026 AFA of +RM0.0367/kWh is a dated example for its own billing month, not a value for another month [source]. The sizing tool itself uses energy volume, a generation target and a site-yield assumption; it does not reconstruct the bill or calculate savings.
What four essential inputs does this solar calculator require?
To run the calculation accurately, the tool requires four specific data points without hidden assumptions:
- Billed electricity consumption (unit: kWh for the billing statement period, minimum 1 kWh). Enter the exact units shown on your TNB physical bill or myTNB mobile app.
- Billing cycle period (unit: days, valid range from 1 to 62 days). Enter the exact statement period (typically around 30 days).
- Target gross generation proportion (unit: %, valid range between 1% and 100%). The portion of energy you aim to produce relative to your normalized 30-day baseline. This is a gross production target, not daytime self-consumption and not net bill reduction. [source]
- Site-specific daily solar yield (unit: kWh/kWp/day, valid range greater than 0 up to 10 kWh/kWp/day). No arbitrary default is imposed. This figure is best obtained from an initial roof survey or installer proposal, as local yield depends on roof azimuth, slope tilt, surrounding shade, and geographic microclimate.
How are the sizing formulas and output capacity calculated?
The calculation strictly converts physical energy consumption into estimated DC panel capacity based on the calculator’s stated assumptions:
| Calculation Step | Formula | Scope and Description |
|---|---|---|
| Normalized 30-day consumption | monthly_kwh = kwh × 30 ÷ days | Adjusts statement billing cycles to a standardized 30-day baseline for consistent sizing. |
| Target gross generation | gross_kwh = monthly_kwh × target ÷ 100 | Total volume of solar energy targeted across 30 days; not identical to avoided grid purchases. [source] |
| Estimated panel capacity | kwp = gross_kwh ÷ (yield_day × 30) | Estimated DC rating in kWp required to achieve the targeted gross generation under stated yield assumptions. |
Worked hypothetical calculation example
To illustrate the mathematical process without projecting savings promises, consider the following hypothetical input scenario:
- Billed consumption: 450 kWh [source]
- Billing period: 30 days
- Target gross generation: 80% [source]
- Assumed daily solar yield: 3.5 kWh/kWp/day
Step-by-step arithmetic:
- Normalized baseline consumption: 450 × 30 ÷ 30 = 450 kWh per 30 days. [source]
- Target gross generation: 450 × 80 ÷ 100 = 360 kWh per 30 days. [source] [source]
- Estimated system size: 360 ÷ (3.5 × 30) = 3.4 kWp (rounded to one decimal place). [source]
This worked example serves only as a transparent mathematical baseline. Output values represent gross DC capacity and gross kWh targets, not guaranteed electricity generation or direct monetary savings.
What are the key limitations of preliminary solar sizing?
This calculator provides preliminary capacity guidance rather than a binding engineering or financial feasibility study:
- Not a formal quotation or payback guarantee. Installation costs vary by roof structure, site conditions, cable routing, and hardware specifications — obtain written itemized quotations from registered installers. The tool does not calculate exact equipment pricing, scaffolding costs, switchboard upgrades, return on investment (ROI), or payback timelines.
- No automatic SuRIA rebate entitlement. The government’s SuRIA Home scheme under SEDA provides a one-time cash rebate of RM600/kWac [source] up to a maximum cap of RM3,000 [source] per eligible domestic account. Rebates depend on official inverter rating thresholds (kWac) and national quota allocations. For eligibility criteria, check our SuRIA rebate guide 2026 (BM).
- No structural roof or electrical audit. Actual performance depends on panel temperature coefficients, string inverter matching, wiring topology, and roof integrity. Final proposals require an on-site audit by a registered contractor.
What grid export rules under Solar ATAP must you know?
For grid-connected residential premises under the Energy Commission’s Guidelines for Solar Accelerated Transition Action Programme (GP/ST/No. 60/2025) (effective 1 January 2026 [source] replacing NEM with a 10-year operational period [source]), export credits offset energy charge components within the same billing month, unused credits are forfeited without carry-forward, and export credits cannot offset AFA surcharges [source]. System capacity should therefore be sized around daytime consumption rather than simply maximizing available roof area.
What are the recommended next steps before requesting quotes?
- Note down your billed kWh consumption and statement days from your latest TNB electricity bill.
- Request an initial roof assessment from a SEDA-registered photovoltaic service provider (RPVSP) to determine an expected daily yield figure.
- Input your figures into the calculator to check your preliminary kWp capacity band.
- Ask at least two registered installers for written proposals on the same scope: panel kWp, inverter kWac and models, roof/electrical work, application fees, exclusions, service/warranty and total project cost before any conditional rebate. If financing is offered, compare the contract total and finance charges separately from the instalment. The calculator’s gross-generation target is not bill savings; compare each proposal’s generation assumptions, daytime self-use and export credit actually available under ATAP before choosing a size. [source]
Read also: Residential solar installation cost (BM) · 10kW solar system price range · SuRIA rebate guide 2026 (BM) · TNB RP4 tariff explained (BM)
Frequently asked questions
solar panel calculator malaysia
For a Malaysian home, an honest calculator converts billed kWh into estimated kWp — nothing else. This tool takes consumption in kWh, billing days, a gross generation target and a site yield, with stated input bounds [source]. If a proposed inverter exceeds 5 kWac single-phase or 15 kWac three-phase, the CCC review path applies [source] — confirm the account class on the bill rather than inferring it from the kWp figure.
solar roi calculator malaysia
A kWp sizing calculator is not an ROI calculator. Real returns need a written quotation, your TNB account category, daytime usage patterns and the AFA rate of the billing month — under ATAP, export credits only offset the energy charge component within the same billing month, with no carry-forward [source]. Any tool promising an ROI figure without those inputs is projecting, not calculating.
Why does this calculator require billed kWh instead of the total bill amount?
The payment total on an electricity bill depends on the account tariff category, bill components and dated adjustments. Solar hardware sizing depends directly on the physical electricity volume consumed in kWh and the number of billing days.
Why is the gross generation target not equal to bill savings?
Gross generation targets the total energy volume produced by the system. Actual bill savings depend on daytime consumption patterns, grid export rules, and applicable tariff rates.
Why does the calculator not provide a default daily solar yield?
Daily generation per unit capacity varies with roof orientation, tilt, surrounding shade, and local weather. Assuming a fixed default value can mislead system sizing.
Is this calculation a binding quotation or engineering guarantee?
No. The calculation provides preliminary sizing arithmetic only. Ask a qualified provider to assess the site, confirm equipment compatibility and state the design, application route and final price in writing; this calculator does not provide those assessments.