DC/AC Ratio Calculator
Enter array DC size, inverter AC rating and sun hours to get the DC/AC ratio and a screening estimate of how much energy clipping wastes at peak sun.
Last updated: 2026-09-28
How the calculation works
- The ratio is simply array watts over inverter watts — the design lever between energy harvest and inverter cost.
- Clipping is estimated from peak-hour production: when the array's peak output exceeds the AC rating, the excess is lost.
- The screening formula assumes ~15% of the day's ideal energy arrives in the peak hour — a practical single-digit estimate, not a simulation.
Formula
DC/AC ratio = Wp_DC ÷ W_AC clipping ≈ f(peak-hour production vs AC rating)
| Symbol | Meaning | Unit |
|---|---|---|
ratio | DC-to-AC ratio | :1 |
PSH | Peak sun hours | h/day |
Worked example
Interpreting the result
Mild oversizing (1.15-1.30) usually pays: the array fills morning, evening and cloudy-day production cheaply while the inverter runs at its most efficient flat-top. Clipping losses at 1.2-1.3 are typically 1-3% annually — less than the energy the oversizing gains. Beyond 1.4, verify the inverter's maximum DC input power: many models accept limited oversizing regardless of the clipping math.
Assumptions
- Screening estimate: real clipping depends on orientation, climate, temperature and inverter curve — PVsyst-grade results need simulation.
- Peak-hour share of daily energy ~15% for a fixed-tilt array.
Limitations
- Does not model inverter temperature derating, voltage windows or multi-MPPT allocation.
- Not suitable for DC-coupled storage systems where clipped energy charges batteries.
Frequently asked questions
What DC/AC ratio should a solar system have?
1.15-1.30 is the modern residential norm. It costs little and captures morning/evening energy, while clipping losses stay in the 1-3% range.
Is clipping bad?
A little is efficient design — the inverter that never clips is probably undersized on DC and idle at peak sun. Losses beyond ~5% annually suggest re-balancing the array or adding storage to capture the excess.