About the Inverter Sizing
Inverter sizing determines the right AC inverter rating for a given solar array, set by the DC-to-AC ratio (also called the inverter loading ratio, ILR). Correct sizing maximizes energy harvest while keeping clipping losses acceptable.
Formula
Inverter AC rating (kW) = DC array size (kWp) ÷ ILR
- DC array size
- Total module rating (kWp)
- ILR
- DC/AC ratio, typically 1.1–1.3 for Indian conditions
How to calculate it
- 1Total the module DC capacity (kWp) of the array.
- 2Choose a DC/AC ratio — 1.1–1.2 for high-irradiance sites, up to 1.3 where mornings/evenings dominate.
- 3Divide DC capacity by the ratio to get the target inverter AC rating.
- 4Verify the array's string voltage/current stays within the inverter's MPPT window and maximum input across the temperature range.
Worked example
A 5.5 kWp array with a 1.2 DC/AC ratio needs about a 4.6 kW inverter — commonly rounded to a standard 5 kW unit. Slight over-sizing of the array relative to the inverter is intentional and improves overall yield.
What you can calculate
- kVA recommendation
- DC:AC ratio
- Phase matching
- Thermal derating
Standards & references
Frequently asked questions
Can the solar array be larger than the inverter?
Yes — and it usually should be. A DC/AC ratio of 1.1–1.3 means the array is oversized relative to the inverter. This captures more energy in low-light hours; the small amount of 'clipping' at peak noon is more than offset by the extra morning/evening harvest.
What happens if the inverter is undersized or oversized?
An undersized inverter (very high DC/AC ratio) clips too much peak generation. An oversized inverter runs inefficiently at partial load and costs more. The 1.1–1.3 range balances both for Indian irradiance.
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