Solar: DC/AC Ratio (Inverter Load Ratio)

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Solar arrays are deliberately oversized against their inverters, because panels almost never hit their nameplate rating. The DC/AC ratio is how designers keep that oversizing in the sweet spot instead of throwing away energy.

Quick formula: Array DC over inverter AC:

=ROUND(B2/C2,2)

A 9.6 kW array on a 7.6 kW inverter is a 1.26 ratio — comfortably inside the typical 1.1 to 1.3 design window.

Functions used (tap for the full reference guide):

ROUND

The example

Three system designs with their array and inverter ratings in kilowatts.

	A	B	C	D
1	System	Array DC (kW)	Inverter AC (kW)	DC/AC
2	Home array	9.6	7.6	1.26
3	Shop roof	14.4	11.4	1.26
4	Ground mount	20.0	20.0	1.00

The formula

One division, rounded to the two decimals the industry quotes:

=ROUND(B2/C2,2) // array DC rating divided by inverter AC rating

How it works

Why the ratio is deliberately above 1:

B2 is the array's nameplate DC rating — panel wattage times panel count, at standard test conditions the array will rarely see.
C2 is the inverter's continuous AC output rating.
B2/C2 gives the ratio. Above 1.0 means the array can, in theory, overwhelm the inverter on a perfect day — which is fine, because most days are not perfect.
ROUND(...,2) gives the 1.26 that appears on the design document.

Push too far past 1.3 and the inverter starts clipping real production on clear days. Sit at 1.0 and you have paid for inverter capacity that almost never gets used.

Try it: interactive demo

Interactive

Enter the array and inverter ratings in kilowatts.

Array DC (kW)

Inverter AC (kW)

Variations

Flag designs outside the window

Let the sheet catch a mis-sized inverter before the order goes in.

=IF(OR(D2<1.1,D2>1.3),"Review","OK")

Array DC from panel count

Build the DC rating rather than typing it.

=E2*F2/1000

Pitfalls & errors

Compare the same units. Panel ratings come in watts and inverters are often quoted in kilowatts — mixing them gives a ratio of 1,260 instead of 1.26.

The right ratio depends on climate and orientation. Cooler, cloudier sites tolerate more oversizing than a hot desert array that regularly runs near nameplate.

Practice workbook

📊

Download the free Solar: DC/AC Ratio (Inverter Load Ratio) practice workbook

Edit the yellow DC and AC rating cells; the ratio recalculates.

Frequently asked questions

Is clipping always bad?

No. A modest amount of clipping on a handful of peak hours is usually cheaper than buying a larger inverter, which is exactly why designs sit above 1.0 on purpose.

Does this change with microinverters?

The same ratio applies, just per panel — panel DC watts over microinverter AC watts. The healthy range is similar.

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Function references: ROUND