Solar Inverter Sizing Calculator

Work out solar inverter sizing instantly with clear inputs, formula shown and shareable results.

About Solar Inverter Sizing Calculator

Inverters are deliberately undersized relative to the DC array because peak output occurs for only a few hours a year. A DC to AC ratio of 1.15-1.35 maximises energy per unit of inverter cost, accepting 1-3% clipping at midday in exchange for better utilisation and lower capital cost.

Formula

Inverter sizing

AC capacity required = DC capacity / DC:AC ratio; units = ceil(AC required / unit rating)

Worked example

With the default values below, Solar Inverter Sizing Calculator returns Inverters Required of 4. Change any input above and every figure here is recalculated in your browser.

Inputs used

DC Array Capacityminimum 0 kWp: 1,200 kWp
Target DC To AC Ratioaccepts 0.5–2: 1.25
Inverter Unit Ratingminimum 0.01 kW AC: 250 kW AC
Acceptable Clipping Lossaccepts 0–15 %: 2 %

Results

Inverters Required: 4
AC Capacity Required: 960.00
Installed AC Capacity: 1,000.00
Actual DC To AC Ratio: 1.2000

Step by step

1Values used
2Inverter sizing
3Inverters Required= 4
4AC Capacity Required= 960.00
5Installed AC Capacity= 1,000.00
6Actual DC To AC Ratio= 1.2000

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is clipping acceptable?

The array only exceeds the inverter rating during a small number of high-irradiance hours. Sizing the inverter for that peak costs far more than the energy clipped.

What DC:AC ratio is optimal?

It depends on the irradiance profile and the tariff. Higher ratios suit diffuse climates and tariffs that reward morning and evening output; lower ratios suit clear desert sites with midday-weighted value.