8 kW DC array, Phoenix
Ratio 1.15 → 7.0 kW inverter, ~0% clip. Ratio 1.30 → 6.15 kW inverter, ~0.4% clip. Save $400, lose 50 kWh/yr.
Solar inverter sizing calculator
What size inverter do I need for my solar array?
NREL and SEIA recommend a DC:AC ratio of 1.15–1.30. Higher ratios cost less per AC watt but cause midday clipping. Find the sweet spot for your location.
Inverter Sizing
Inverter sizing & DC current
Recommended inverter1,875 W
Continuous requirement (NEC 125%)1,875 W
Surge requirement3,500 W
Continuous DC amps34 A
Peak DC amps79.3 A
Results are first-pass estimates. Verify with installers, manufacturers, and utility tariffs before purchase.
How it works
How it works
- Inverter kW = array DC kW ÷ target DC:AC ratio. Common targets: 1.15 (high-irradiance), 1.25 (moderate), 1.30 (cloudy/north).
- Clipping ≈ max(0, (ratio − 1.15)² × 18%). Hard-clip occurs only on the sunniest 100–200 hours/year.
- Annual clipped energy = clipping × annual production. Budget 0.5–2% loss vs avoided inverter cost.
Worked examples
Worked examples
10 kW DC, Boston
Ratio 1.25 → 8.0 kW inverter, ~0.2% clip. Cloudier climate tolerates higher ratio with negligible clipping.
Microinverter array
Enphase IQ8M (330 W AC) on 400 W panels → 1.21 ratio, ~0.1% clip. No need to oversize.
Inverter sizing FAQ
Inverter sizing FAQ
Why oversize the DC array at all?
Panels almost never produce nameplate watts — temperature, soiling, and azimuth losses mean real peak is 80–85% of DC rating. Oversizing recovers that.
Will clipping shorten inverter life?
No. Inverters are designed to ride at AC limit indefinitely. Heat dissipation matters more — ventilate per manufacturer specs.
When should I use microinverters?
Partial shade, multiple roof orientations, or rapid shutdown requirements (NEC 2017+). Microinverters cost 15–30% more but waste less on shade.
How does clipping affect ITC?
ITC applies to total system cost regardless of clipping. Clipping is energy loss, not cost loss.
Solar Calculators
Solar Panel & PV System Calculators
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Size a solar PV array from your daily electricity use, local peak sun hours, system losses, and panel wattage. Also estimates roof area and an off-grid battery bank using depth-of-discharge and round-trip efficiency.
Open calculatorSolar payback calculator
Apply the 30% federal ITC, model 0.5%/year panel degradation and 3%/year rate inflation, and see year-by-year cumulative savings until the system breaks even.
Open calculatorNet metering calculator
Compare a solar bill under traditional 1:1 net metering vs export-only credits (e.g. CA NEM 3.0). Get monthly net cost, exported kWh, self-consumption ratio, and annualized totals.
Open calculatorSolar panel tilt calculator
Get the year-round optimal tilt (≈ latitude), summer tilt (latitude − 15°) and winter tilt (latitude + 15°), plus expected production gain from seasonal adjustment.
Open calculator