Solar DC to AC Ratio Calculator

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Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

Solar panel DC size: The total nameplate power of the solar panels before inverter losses, entered in kilowatts (kW).

Inverter AC rating: The inverter's continuous output power rating in kilowatts (kW).

DC to AC ratio: Solar panel DC size divided by inverter AC rating. It is unitless because kW divided by kW cancels out.

Target DC to AC ratio: The ratio you want the candidate inverter sizes to be compared against.

Gap from your target ratio: The absolute distance between a candidate ratio and your target ratio, measured in ratio points.

Inverter size comparison table: A sorted table that shows each compared inverter size, its DC to AC ratio, and its gap from the target.

Mistake: Entering one panel's wattage in Solar panel DC size instead of the whole array size.
Fix: Convert total panel nameplate watts to kW, such as 16 panels x 400 W = 6.4 kW.

Mistake: Using inverter surge power for Inverter AC rating .
Fix: Use the continuous AC rating in kW so the ratio matches normal solar sizing language.

Mistake: Leaving Target DC to AC ratio blank or typing 0.
Fix: Enter a positive target ratio, such as 1.25, so the comparison table can measure the gap.

Mistake: Typing ranges or formulas in Other inverter sizes to compare , such as 4-6 or 6.4/1.25.
Fix: Enter separate positive inverter sizes only, such as 4, 5, 5.2.

Mistake: Reading Compared inverter closest to your target as the final design choice.
Fix: Treat it as a quick screening result and still check equipment specs, local rules, and installer guidance.

• This calculator uses nameplate kW values only. It does not estimate clipping, yearly energy, weather effects, shade, roof angle, or money impact.
• The closest inverter is closest only to the Target DC to AC ratio you entered. The calculator does not decide the best ratio for a roof, climate, utility rule, or equipment warranty.
• Candidate inverter sizes must be positive single numbers in kW. Invalid entries are skipped, and duplicate sizes are kept only once.
• If two compared inverter sizes are exactly the same distance from the target ratio, the earlier one in the comparison list is kept as the closest match.
• Real projects may need electrical code checks, inverter voltage/current limits, module compatibility checks, and local permitting review.

Ratio calculation

The calculator uses the standard solar sizing idea that the DC to AC ratio compares the solar array's DC nameplate size with the inverter's AC rating [1]. Both values must be positive and in kW.

current_ratio = dc_size_kw / ac_size_kw

Candidate comparison

The entered Inverter AC rating is added first to the comparison pool. The calculator then reads Other inverter sizes to compare, keeps positive single-number entries, removes duplicates, and skips invalid entries with a note.

candidate_ratio_i = dc_size_kw / candidate_ac_kw_i

gap_i = abs(candidate_ratio_i - target_ratio)

The closest compared inverter is the candidate with the smallest gap. If two candidates tie at full precision, the one that appeared earlier is used.

closest_ac_kw = candidate_ac_kw_i where gap_i is smallest

Mini-example

For a 6.4 kW solar panel DC size and a 5 kW inverter AC rating, the current ratio is 6.4 / 5 = 1.28. With a target ratio of 1.25 and comparison sizes of 3.8, 4, and 5.2 kW, the 5.2 kW candidate gives 6.4 / 5.2 = 1.230769. Its gap from the target is abs(1.230769 - 1.25) = 0.019231 ratio points, so it is closer than the other compared sizes.