Estimate monthly bill reduction, yearly savings, and rough payback for a home solar setup.
Quick planning, rough comparisons, and checking whether your assumptions are in the right range before you rely on final quotes or advice.
Review the assumptions below, then compare with related calculators if your decision depends on rates, eligibility, or provider-specific rules.
How this calculator works
- Monthly savings are estimated from the difference between the current bill and the post-solar bill, after subtracting a simple maintenance budget.
- Annual savings are the monthly savings multiplied by 12.
- Rough payback period equals the system cost divided by monthly savings.
Worked example
If your bill drops from LKR 18,000 to LKR 4,500 and you budget LKR 500 per month for maintenance, the net monthly saving is about LKR 13,000.
Important assumptions
- This is a simple planning model and does not include financing, inverter replacement, or export-credit rules.
- Electricity tariff changes and weather-driven production changes are not modeled separately.
- Maintenance is treated as a flat monthly budget for easy comparison.
Methodology and review
Shared calculator template reviewed for formula clarity and on-page transparency.
Editorial review focuses on practical accuracy, assumptions, and user-facing clarity.
This page is meant for comparison and budgeting, not as a formal loan, deposit, or investment offer.
How this calculation is produced
- This tool converts your amount, rate, and term inputs into an estimate using the finance formula defined for the calculator.
- The result is intended to help compare scenarios quickly before you rely on lender-specific fees, taxes, penalties, or product conditions.
- If the underlying product uses a different compounding method or pricing structure, the final real-world number may differ from the estimate shown here.
What to verify before relying on it
- Verify lender rates, compounding, fees, and eligibility rules against the relevant bank or provider before making a commitment.
- Compare the output with official product documents or current rate tables when the decision affects borrowing or savings.
- Use the result for screening and negotiation, then confirm details with the provider or a qualified adviser.
When this tool is useful
- Use this to pressure-test affordability before speaking to banks or lenders.
- Use it when comparing several rates, terms, or savings timelines side by side.
- Use it again whenever rates, tenure, or contribution assumptions change.
How to read the result
- Focus on the total cost and monthly cash-flow impact, not only the headline rate.
- Use the result as a planning estimate before final lender fees, taxes, or eligibility checks.
- If the tool shows several metrics, compare the tradeoff between payment size and total cost over time.
Common mistakes
- Comparing offers by monthly payment alone while ignoring total interest or maturity value.
- Using rates that do not match the real bank product, compounding method, or fee structure.
- Forgetting that approval conditions and documentation can change the final offer.
Good next steps
- Compare this output with rate pages, bank tables, or a second related calculator.
- Check whether fees, taxes, insurance, or penalties need to be added before deciding.
- Keep a margin of safety in the budget instead of planning at the absolute limit.
FAQ
Are these calculators free?
Yes. lankacalculator tools are free to use and designed to be quick to access without sign-up.
How accurate are the results?
The calculators use clear assumptions and formulas, but results are estimates and should be checked against official documents or provider terms.
Can I use this on mobile?
Yes. The layout is built to work cleanly on phones, tablets, and desktops.
Do you store my inputs?
No account is required for these tools, and calculator inputs are not stored as user profiles in this v1 setup.