Size solar inverters using running, surge, and reserve. Compare watts, VA, current, and daily energy. Build dependable systems with smarter capacity planning from outset.
Use the advanced settings below, then enter appliance loads. The layout stays single-column overall, while the calculator fields use a responsive 3/2/1 grid.
| Appliance | Qty | Running Watts Each | Surge Multiplier | Hours/Day | Critical |
|---|---|---|---|---|---|
| LED Lights | 8 | 12 | 1.0 | 5 | Yes |
| Ceiling Fans | 4 | 75 | 1.5 | 8 | Yes |
| Refrigerator | 1 | 180 | 3.0 | 10 | Yes |
| Laptop | 2 | 90 | 1.1 | 6 | Yes |
| Water Pump | 1 | 750 | 3.5 | 1 | No |
| Television | 1 | 120 | 1.2 | 4 | No |
Running watts per load = Quantity × Running watts each
Surge watts per load = Running watts per load × Surge multiplier
Daily energy per load = Running watts per load × Hours per day
Base running demand = Total running watts × Demand factor
Continuous inverter requirement = Base running demand × (1 + Safety margin) × (1 + Future expansion)
Surge inverter requirement = Continuous inverter requirement + [(Total surge extras) × Surge overlap factor]
Recommended VA = Recommended inverter watts ÷ Power factor
DC current at full load = Recommended inverter watts ÷ (System voltage × Inverter efficiency)
Battery Ah for backup = Critical running watts × Backup hours ÷ (System voltage × Usable DoD × Inverter efficiency)
Suggested solar array watts = Critical daily energy ÷ (Peak sun hours × Solar performance factor)
Running watts are the steady power a device needs after startup. Surge watts are the brief extra demand during startup. Motors, compressors, and pumps usually need higher surge capacity.
A margin covers inverter heat, cable losses, aging, uncertain labels, and future appliances. It reduces nuisance shutdowns and gives the system room to operate reliably.
Not necessarily. Solar array size affects energy production over time, while inverter size handles instantaneous AC load and startup demand. Both must be matched carefully, but they solve different sizing problems.
For most homes and sensitive electronics, pure sine wave output is the safer choice. It supports motors, chargers, and control boards more smoothly than modified wave designs.
Power factor helps estimate apparent power in VA, which some inverters publish. Lower power factor means the inverter may need more VA capacity than the watt rating alone suggests.
Use the battery bank voltage the inverter will actually use, such as 12V, 24V, or 48V. Higher voltage reduces current, cable thickness, and stress in larger systems.
Battery size depends on critical load, backup hours, system voltage, inverter efficiency, and usable depth of discharge. This calculator gives a planning estimate, not a final engineering design.
No. It is a practical sizing aid for planning. Final system design should still verify surge behavior, wiring, protection devices, ambient conditions, battery chemistry, and local electrical requirements.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.