Inverter Sizing Calculator Formula
Understand the math behind the inverter sizing calculator. Each variable explained with a worked example.
Formulas Used
Recommended Inverter Size
inverter_size_w = total_panel_watts / dc_ac_ratioInverter Size (kW)
inverter_size_kw = total_panel_watts / dc_ac_ratio / 1000DC Oversize Headroom
clipping_headroom = (dc_ac_ratio - 1) * 100Variables
| Variable | Description | Default |
|---|---|---|
total_panel_watts | Total Panel Wattage (DC)(W) | 8000 |
dc_ac_ratio | DC-to-AC Ratio | 1.2 |
How It Works
Solar Inverter Sizing
The inverter converts DC power from solar panels to AC power for home or grid use. It is typically sized smaller than the total panel capacity.
Formula
Inverter Size (W) = Total Panel Wattage / DC-to-AC Ratio
A DC-to-AC ratio of 1.1-1.3 is standard. This means the inverter is smaller than the panel array. This is efficient because panels rarely produce their full rated power simultaneously. A ratio of 1.2 means 20% overbuilding on the DC side, which captures more energy during low-light hours with minimal clipping losses at peak.
Worked Example
An 8 kW (8,000 W) panel array with a 1.2 DC-to-AC ratio.
- 01Inverter size = 8,000 / 1.2 = 6,667 W
- 02That is a 6.67 kW inverter
- 03DC oversize headroom = (1.2 - 1) x 100 = 20%
Frequently Asked Questions
Why not match inverter to panel size exactly?
Panels rarely reach rated output. A smaller inverter saves money and still captures nearly all the energy. Clipping losses at peak are typically under 1-2% annually.
What DC-to-AC ratio should I use?
A ratio of 1.15-1.25 is common for residential systems. Higher ratios (up to 1.5) are used in cloudy climates to maximize low-light capture.
What happens if the inverter is too small?
If DC power exceeds inverter capacity, the inverter clips output at its maximum rating. Some energy is lost, but the system is not damaged.
Ready to run the numbers?
Open Inverter Sizing Calculator