Your result
Click Calculate
Enter your values, then click Calculate result.How this calculator helps
Add the running wattage of the appliances you want to power and allow capacity for losses and short peaks. The result converts watts into an estimated VA requirement and suggests the next practical minimum size.
UPS and Battery Sizing Guide for Pakistan
Size inverter VA, battery Ah and expected backup time without confusing watts, volt-amperes and watt-hours.
Read the complete guide →How to use it
- 1
Add the running watts from appliance labels or reliable measurements.
- 2
Choose safety headroom and use the inverter manufacturer's power-factor guidance.
- 3
Check that both continuous and surge ratings support the intended appliances.
Formula and methodology
Required VA = connected watts × (1 + safety margin) ÷ power factor. Motors and compressors may also require separate surge capacity.
Uses the values you enter with transparent energy, power and efficiency relationships. Provider tariffs and equipment specifications should be replaced with current figures.
Worked calculation example
A planned 800 W running load with 25% headroom and a 0.8 power factor produces a minimum estimate of 1,250 VA before checking startup surges.
How to interpret your result
Choose an inverter above the calculated running requirement and separately confirm the largest motor or compressor startup surge.
Input guide
Total only appliances expected to operate simultaneously.
Use realistic power factor where VA matters.
Keep safety headroom for variation and future additions.
Scenario comparison
| Scenario | What it demonstrates |
|---|---|
| 500 W electronic load | mainly a running-power comparison. |
| 1,000 W plus refrigerator | requires explicit surge review. |
| Mixed fans, pump and appliances | check both VA and startup sequence. |
Common mistakes to avoid
- Selecting an inverter using watts while ignoring VA.
- Treating startup surge as continuous load.
- Using the advertised maximum instead of continuous rating.
Compare continuous power, surge duration, DC voltage and protection requirements on the inverter datasheet.
What can affect the result?
Startup surge
Motors, pumps and compressors can briefly draw much more than running watts.
Power factor
Some loads require more volt-amperes than their watt figure suggests.
Future expansion
Planned appliances should be included before choosing the inverter size.
Limits of this estimate
This sizing aid does not replace appliance-by-appliance surge measurement, cable sizing, protection design or an electrician's assessment.
Sources and review information
Frequently asked questions
Is the inverter load calculator 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.
Do refrigerators need special allowance?＋
Yes. Compressors and pumps can draw several times their running power briefly, so verify the inverter's surge rating.