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Solar sizing & payback · Homeowners & NRN clients

Rooftop Solar System Size & Cost Calculator Nepal

Size a rooftop solar system from your monthly electricity units and local sun hours, then estimate panel count, roof area, system cost, battery cost and simple payback years.

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Example rates only — replace with local quotes

Installed cost per kW in Nepal varies widely with panel and inverter brand, roof structure and whether net metering is included. Batteries are the single biggest cost driver—an on-grid system with net metering is usually far cheaper per unit saved than a battery-backed hybrid. Confirm current NEA net-metering rules and your actual tariff slab before committing.

Enter your project details

Your estimate

A rooftop solar system sized from your actual consumption, with installed cost and a simple payback period.

Daily consumption
6.7 kWh

200 units per month ÷ 30

Required system size
1.98 kW

6.7 kWh ÷ (4.5 sun hours × 0.75 performance ratio)

Panels needed
4 nos

at 550 W per panel

Unshaded roof area needed
198 sq. ft.

≈ 100 sq. ft. per kW including walkways and tilt spacing

Solar system cost
NPR 177,778

1.98 kW × NPR 90,000

Battery bank
Not included (on-grid)

On-grid systems export surplus instead of storing it

Total installed cost
NPR 177,778
Annual generation
2,433 kWh

203 kWh per month on average

Annual bill saving
NPR 26,767

at NPR 11 per unit

Simple payback
6.6 years

Cost ÷ annual saving. Ignores tariff changes, panel degradation, inverter replacement and finance cost.

Planning estimate only—not a solar design or a guarantee of generation. Actual output depends on shading, roof orientation and tilt, dust, temperature, inverter selection and grid availability. A site survey, structural check of the roof, and confirmation of net-metering eligibility with your NEA distribution centre are required before purchase.

What this estimate assumes

Where solar estimates usually go wrong

  • Size from consumption, not roof space. A system larger than your usage exports cheaply or wastes generation.
  • The performance ratio (typically 70–80%) absorbs inverter losses, cable losses, dust, heat and wiring mismatch. It is why a 1 kW panel never gives 1 kWh per sun hour.
  • Peak sun hours are not daylight hours. Most of Nepal sits around 4–5 equivalent full-sun hours a day averaged over the year.
  • Shading from a neighbouring building, a water tank or a single tree branch can cut a string's output disproportionately. Survey the roof at different times of day.

Formulas used

  • Required kW = (monthly units ÷ 30) ÷ (peak sun hours × performance ratio)
  • Annual generation = kW × sun hours × performance ratio × 365
  • Total cost = kW × cost per kW + battery kWh × battery rate
  • Simple payback = total cost ÷ (annual generation × tariff)

Practical guide

Understand the numbers before you use them on site

Read the related guide for assumptions, ordering tips and ways to compare the estimate with actual site records.

Read guide

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Frequently asked questions

Use the estimate with confidence

Is the Rooftop Solar Cost free?

Yes. The Rooftop Solar Cost works in your browser without an account. You can install GharNaksa when you want to track the real project costs, payments and progress.

Can I use this result as a final quotation or professional approval?

No. It is a planning estimate based on the information you enter. Verify rates, quantities, drawings, local requirements and contract terms with the appropriate qualified professional before making a commitment.

How do I track the estimate during construction?

Use GharNaksa to record actual material deliveries, labor, payments, bills and site photos. Comparing the estimate with a dated site record helps reveal cost differences early.