Going Solar: How to Size a System and Estimate the Savings
A practical guide to home solar — understanding your usage, how many panels you need, sizing the inverter and battery, net metering, the payback period and the carbon you save.
Inverter Size Calculator
Verified formula Updated Jun 2026 Private — runs on your device
Verified formula
Private
Inverter size needed
1,000
For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.
How to use the Inverter Size Calculator
The Inverter Size Calculator works out your inverter size needed in an instant. Enter total load and power factor and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.
- Enter the total load.
- Enter the power factor.
- Read off your inverter size needed — the calculator updates automatically, with no button to press.
Formula
The Inverter Size Calculator uses the formula:
Inverter size needed = Total load ÷ Power factor
Worked example
For example, with total load of 800 W and power factor of 0.8, the inverter size needed is 1,000.
| Total load | 800 W |
|---|---|
| Power factor | 0.8 |
| Inverter size needed | 1,000 |
|---|
Results are estimates for educational use, not professional advice.
Frequently asked questions
Divide your total load in watts by the power factor. An 800 W load at a 0.8 power factor needs a 1000 VA inverter.
It is the ratio of real power (watts) to apparent power (VA). Inverters are rated in VA, so the load is divided by it to size them.
A little. Leaving 20–25% headroom handles surges and future loads, and keeps the inverter from running at full capacity continuously.
No. The inverter VA handles instantaneous load. Battery capacity, sized separately, determines how long it can run.
The Inverter Size Calculator uses the formula: Inverter size needed = Total load ÷ Power factor. For example, with total load of 800 W and power factor of 0.8, the inverter size needed is 1,000.
Enter the total load. Enter the power factor. Read off your inverter size needed — the calculator updates automatically, with no button to press.
Related guides
Inverter Size Table: Inverter size needed by Total load
Reference table of inverter size needed for Inverter Size across a range of total load values — exact, engine-computed figures you can read off at a glance.
How to Calculate Inverter Size: Formula, Steps & Examples
Learn how to calculate Inverter Size — the formula explained step by step, with worked examples and a free calculator to check your answer.