Your result
Click Calculate
Enter your values, then click Calculate result.How this calculator helps
Estimate inverter capacity from running load, surge and headroom. The calculation keeps important tariff, equipment and usage assumptions visible so visitors can replace defaults with their own bill, datasheet or measured values.
How to Size a Solar System in Pakistan
Calculate solar kW, panel count, inverter capacity and realistic generation from your own electricity use.
Read the complete guide →How to use it
- 1
Copy current values from a bill, equipment label, datasheet or measurement.
- 2
Enter realistic operating hours, rates and system losses rather than best-case marketing figures.
- 3
Use the result for comparison and obtain qualified electrical design where safety or installation is involved.
Formula and methodology
Inverter VA = (running watts + surge watts) × headroom ÷ power factor.
Uses editable energy demand, sunlight, equipment and loss assumptions. It is a planning model rather than a site survey or electrical design.
Worked calculation example
A 3,000 W load plus 1,500 W surge needs additional design margin.
How to interpret your result
Use the calculated VA as a minimum planning size, then verify DC window, surge and array compatibility.
Input guide
Total simultaneous AC running watts.
Add the largest realistic startup surge.
Use a defensible power factor and headroom.
Scenario comparison
| Scenario | What it demonstrates |
|---|---|
| 3,000 W running plus 1,500 W surge | tests a common mixed-load case. |
| Motor-heavy load | may need more surge capacity than resistive loads. |
| Future-load scenario | adds headroom without extreme oversizing. |
Common mistakes to avoid
- Selecting by marketing kW alone.
- Ignoring DC voltage and MPPT limits.
- Assuming surge rating can be sustained continuously.
Match the final design against the manufacturer's complete datasheet and a qualified electrical design.
What can affect the result?
Tariffs and adjustments
Provider rates, taxes, fuel adjustments and export rules can change by billing period.
Real operating conditions
Temperature, dust, voltage, cycling, shade and user behaviour change energy results.
Safety and compatibility
Surge, cable protection, equipment limits and installation standards need professional checking.
Limits of this estimate
This planning estimate cannot reproduce every provider bill, inspect a site, certify wiring or equipment, predict weather, or replace a qualified electrical or solar design.
Sources and review information
Frequently asked questions
Is the solar inverter size free?＋
Yes. SolvePilot tools are free, work in your browser, and require no account.
Does SolvePilot store my values?＋
No. Calculations run locally in your browser and the values you enter are not sent to a server.
Should I treat the result as an exact bill or quotation?＋
No. Results are informed estimates. Final charges can vary because of taxes, tariffs, lender terms, usage patterns, or provider rules.
How can I improve the accuracy?＋
Use recent values from your own bill, statement or institution, review every assumption, and confirm important results with the relevant official source.
Is this an official bill or engineering design?＋
No. It is a planning estimate. Confirm tariffs with the provider and safety-critical equipment, wiring and protection with a qualified professional.