Free Calculator
Solar Inverter Sizing Calculator
Find the right inverter AC size from your array's DC size using the DC:AC (inverter load) ratio — and see the nearest common inverter and clipping risk before you order equipment.
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Size Your Solar Inverter
Enter your array's DC size and target DC:AC ratio to see the recommended inverter AC size, the nearest common inverter, and your clipping risk.
Sum of all panel wattages ÷ 1000. E.g. 20 × 400W panels = 8 kW.
Used only as a suggested-ratio nudge. Your chosen DC:AC ratio above drives the math.
📋 Important: All calculator results are ballpark estimates
The figures shown are approximate estimates based on typical averages and should be used for general planning purposes only. They are not a substitute for a professional assessment or written contractor quote. Actual costs, savings, and results will vary significantly based on your specific circumstances, local market conditions, equipment choices, and contractor pricing. Always confirm any estimate with a licensed contractor, financial advisor, or qualified professional before making purchasing or financial decisions.
How Solar Inverter Sizing Works
The DC:AC ratio (inverter load ratio)
Inverter sizing comes down to one number: the DC-to-AC ratio, also called the inverter load ratio (ILR). It is the array's DC nameplate size divided by the inverter's AC rating. A ratio of 1.2 means the array's DC capacity is 20% larger than the inverter's AC output. Most residential systems are designed between 1.1 and 1.3, and the calculator above turns your target ratio into a recommended inverter size.
| DC:AC ratio | Typical use |
|---|---|
| 1.1 | Conservative — cloudy/northern climates, minimal clipping |
| 1.2 | Recommended default for most residential systems |
| 1.25 | Sunny climates where extra DC still pays off |
| 1.3 | Aggressive — accepts more clipping to maximize weak-light output |
Solar contractors managing installs at scale track sizing, proposals, and equipment in one place with Solar Contractor Software.
Why slight DC oversizing (1.2) is standard
Panels almost never hit their nameplate DC rating in the field — heat, wiring losses, dust, soiling, and off-angle sun all shave real output. Sizing the DC array about 20% larger than the inverter keeps the inverter operating closer to its efficient range for more of the day and boosts total annual energy harvest. Because inverter capacity is more expensive per watt than adding a couple of panels, a 1.2 ratio is usually the most cost-effective design — you capture more morning, evening, and cloudy-day production without paying for a bigger inverter.
What clipping is — and why a little is fine
Clipping happens on peak-sun moments when the DC array briefly produces more power than the inverter can convert, so the inverter caps its output at its AC rating. The "lost" energy sounds bad, but at a 1.2 ratio it usually amounts to only a couple of percent of annual production — and those few peak hours are more than offset by the extra energy the larger array captures the rest of the day. Clipping only becomes wasteful at high ratios (above roughly 1.3) in very sunny climates, which is why the calculator flags a High clipping risk there.
String inverters vs. microinverters
The sizing ratio applies whether you use a central string inverter or panel-level microinverters — but the design decisions differ:
- String inverters size the whole array (or per-string) against one or a few central units. They're cost-effective on simple, unshaded roofs and make the whole-system DC:AC ratio easy to plan.
- Microinverters / DC optimizers set the ratio at each panel, which helps on shaded or complex multi-plane roofs and improves module-level monitoring.
- Either way, the whole-system AC target this tool gives you is the right starting point — then confirm exact model selection with your equipment supplier and local code requirements.
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Book a Free DemoFrequently Asked Questions
What is the DC-to-AC ratio (ILR) in solar?
The DC-to-AC ratio — also called the inverter load ratio (ILR) — is the array's DC nameplate size divided by the inverter's AC rating. For example, an 8 kW DC array on a 6.6 kW AC inverter has a ratio of about 1.21. Most residential systems are designed at a 1.1–1.3 ratio, with 1.2 being the common target.
What is the ideal DC-to-AC ratio for a home solar system?
A ratio of around 1.2 is the industry standard for most residential systems. It slightly oversizes the DC array relative to the inverter, which captures more energy in the mornings, evenings, and cloudy days while accepting a tiny amount of clipping at peak sun. Sunnier climates can push toward 1.25; cloudier climates often stay near 1.1.
What is inverter clipping and is it bad?
Clipping happens when the DC array briefly produces more power than the inverter's AC rating, so the inverter caps output at its maximum. A small amount of clipping (a few percent per year) is normal and expected at ratios around 1.2 — the extra DC still boosts production in weaker light. Clipping only becomes wasteful at very high ratios (above ~1.3) in sunny climates.
Why intentionally oversize the DC array relative to the inverter?
Panels rarely hit their nameplate DC rating — real-world output is reduced by heat, wiring losses, dust, and off-angle sun. Oversizing the DC array (a ratio above 1.0) keeps the inverter working closer to its efficient operating range for more of the day and increases total annual energy harvest, usually at a lower cost than upsizing the inverter.
Should I use a string inverter or microinverters?
String inverters size the whole array against one (or a few) central inverters and are cost-effective on simple, unshaded roofs. Microinverters or DC optimizers set the DC-to-AC ratio at the panel level, which helps with shading and complex multi-plane roofs. The sizing ratio still matters for both — this tool gives you the whole-system AC target either way.
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Get a Free DemoAll calculations are ballpark estimates based on typical solar design ratios and should be verified with licensed solar contractors and equipment specifications before making any purchasing decisions.