Inverter Size Calculator
Estimate inverter AC rating from PV array DC kW and a target DC/AC ratio—an instant inverter size calculator for commercial and industrial planning.
Quick answer
Inverter kW ≈ Array kW ÷ DC/AC ratio. Example: 50 kW DC at ratio 1.2 → ~41.7 kW AC inverter. Hub: Solar calculator.
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Inverter Sizing Results
Engineering disclaimer
Planning estimate only. Confirm OEM MPPT windows, clip losses, and interconnection limits. Not a portable inverter shopping tool.
Inverter kW by DC/AC ratio
| DC/AC | Inverter kW |
|---|
People also ask
- How to size PV inverter? Array kW ÷ DC/AC ratio.
- What ratio? Often ~1.1–1.3.
- kVA next? Use kW to kVA with PF.
Planning guidance
This page screens inverter AC rating from array DC nameplate and a target DC/AC ratio. It is a procurement planning step—not a clip-loss or interconnection study.
- Array first: Lock DC kW in solar panel sizing before inverter screens.
- kVA conversion: Use kW to kVA with site power factor.
- Interconnection: transformer sizing for solar and commercial interconnection requirements.
- Off-grid path: Battery systems may use MPPT charge controller sizing instead of—or in addition to—grid inverters.
- Hub: Solar calculator.
Last updated: 2026-08-07. Planning estimate only—confirm OEM ratings and clip losses before procurement.
Typical scenarios
- Commercial roof: Mild oversizing (DC/AC 1.15–1.25) common for cost/yield balance.
- Clip-sensitive site: Prefer ~1.1 and verify yield with PVWatts/SAM.
- Hybrid storage: Coordinate battery inverter ratings separately from PV inverter AC.
Continuous vs surge inverter rating
Continuous AC rating is the sustained output the inverter can deliver under normal PV operation—this is what you size against array DC via DC/AC ratio.
Surge (peak) rating, when listed on hybrid or off-grid inverters, covers brief motor-start or load inrush. PV grid-tie sizing should use continuous kW, not surge peaks.
- Example: 50 kW DC array at DC/AC 1.2 → ~41.7 kW continuous inverter AC needed.
- Do not size a grid-tie string inverter on surge kW from a portable spec sheet.
Continuous / surge load → inverter kW & kVA
For hybrid/off-grid inverters that publish both continuous and surge AC ratings, screen continuous kW first, then convert to kVA at the project PF. Grid-tie string inverters usually ignore surge columns.
| Load continuous | Load surge (brief) | Select continuous kW ≥ | kVA @ PF 0.9 | kVA @ PF 1.0 |
|---|---|---|---|---|
| 3 kW | 6 kW | 3.0–3.5 | ~3.3–3.9 | 3.0–3.5 |
| 5 kW | 10 kW | 5.0–5.5 | ~5.6–6.1 | 5.0–5.5 |
| 10 kW | 20 kW | 10–11 | ~11–12 | 10–11 |
| 41.7 kW (50 kW DC ÷ 1.2) | n/a (grid-tie) | ~42 | ~46.3 | ~42 |
Convert any inverter kW to kVA with the kW to kVA calculator. Surge must still clear motor-start OEM limits separately.
DC/AC ratio and oversized arrays
DC/AC ratio = array DC nameplate ÷ inverter AC continuous rating. Values above 1.0 mean the array is oversized relative to inverter AC—a common commercial strategy.
- Ratio ~1.1: Minimal clipping; inverter runs closer to nameplate on peak days.
- Ratio ~1.25: More DC for morning/evening harvest; expect midday clip on clear days.
- Ratio >1.35: Aggressive—verify energy gain vs clip loss with yield models.
Method context: how to size a commercial solar array.
Inverter sizing by deployment scenario
| Scenario | Array DC | Typical DC/AC | Inverter AC |
|---|---|---|---|
| Off-grid cabin | 5 kW DC | 1.0–1.1 | ~4.5–5.0 kW (often MPPT + hybrid inverter) |
| Small commercial roof | 50 kW DC | 1.15–1.25 | ~40–43 kW AC |
| Large warehouse | 500 kW DC | 1.2–1.3 | ~385–417 kW AC (multi-inverter) |
MPPT charge controller vs grid inverter
- MPPT charge controller (see MPPT sizing): sizes DC current and cold Voc for battery-charging paths—off-grid, hybrid DC-coupled, or DC-coupled BESS.
- Grid/hybrid inverter (this page): sizes AC continuous rating vs array DC for grid-tie or AC-coupled storage.
- Many commercial systems use both in different topologies—do not substitute MPPT amp sizing for inverter kW sizing.
- Topology guide: MPPT vs PWM charge controller (battery path context).
Formula (quick reference)
Inverter kW_AC ≈ Array kW_DC ÷ DC/AC ratio
Inverter kVA ≈ kW_AC ÷ PF
AC interconnection context: transformer sizing for solar systems · commercial solar interconnection requirements.
Formula and sources
Planning screen only. OEM inverter datasheets and interconnection rules govern final selection.
- NREL PVWatts — clip and yield sensitivity to DC/AC ratio
- NREL System Advisor Model (SAM) — inverter and loss modeling
- NFPA / NEC (NFPA 70) — Article 705 interconnection context
Frequently Asked Questions
How do I size a solar inverter?
Divide array DC kW by the target DC/AC ratio. Example: 50 kW DC at ratio 1.2 → ~41.7 kW AC inverter. Then convert to kVA if needed.
What is continuous vs surge inverter rating?
Continuous is sustained AC output under normal PV operation—size on this. Surge covers brief overloads on some hybrid units; do not use surge kW for grid-tie PV sizing.
What is a typical DC/AC ratio?
Commercial rooftops often use 1.1–1.3. Higher ratios increase midday clipping but can improve annual energy—confirm with yield models.
Can I oversize the array vs the inverter?
Yes—DC/AC > 1.0 is deliberate oversizing. Example: 60 kW DC on a 50 kW inverter = ratio 1.2. Verify clip losses before procurement.
Difference from MPPT charge controller sizing?
MPPT sizing is for DC charge controllers (Isc × parallel × SF, cold Voc). This tool sizes grid/hybrid inverter AC rating vs array DC.
Is this for portable inverters?
No—commercial/industrial PV planning, not camping kits or UPS inverter shopping.
How do I convert inverter kW to kVA?
kVA ≈ kW ÷ PF. At PF 1.0, 41.7 kW ≈ 41.7 kVA; at PF 0.9 ≈ 46.3 kVA. See the continuous/surge → kW & kVA table, then use the kW to kVA calculator.
What is the next step?
Convert inverter kW to kVA and review transformer interconnection guidance.
How it works
DC/AC ratio is array DC nameplate divided by inverter AC continuous rating. Solving for inverter kW gives a procurement screen before clip/yield studies.