What This Tool Calculates
This calculator compares a PV array's DC installed capacity against an inverter fleet's AC output capacity, producing the DC/AC ratio and DC loading percentage. It can work from module count and module power, or from a direct DC capacity figure, and checks the result against a manufacturer's maximum DC input power per inverter where that data is available.
How To Use It
- Enter DC capacity — either module count × module power, or a direct DC capacity figure.
- Enter AC inverter capacity and the number of inverters.
- Optionally enter each inverter's maximum DC input power to check for a manufacturer-limit breach.
- Review the DC/AC ratio, DC loading percentage, and per-inverter DC loading.
Engineering Principle
The relationship is a straightforward capacity ratio:
DC/AC Ratio = DC Capacity (MWp) / AC Capacity (MW)
A ratio of 1.25, for example, means the array can produce up to 25% more DC power than the inverter fleet can convert to AC at once. Whether that's appropriate depends entirely on the site's irradiance profile and array orientation — a fixed-tilt array in a low-irradiance climate behaves very differently from a tracker array in a high-irradiance desert site, even at the same nominal ratio.
There Is No Universal Ideal Ratio
Optimisation depends on irradiance, orientation, inverter clipping behaviour, local energy price signals, curtailment exposure and overall project economics. A ratio that's optimal for one site's revenue model can be the wrong choice for another with a different tariff structure or irradiance profile. This calculator reports the ratio and loading figures — it does not claim one number is correct for your project.
Formulas
Pdc = Module Count × Module PowerDC capacityRatio = Pdc / PacDC/AC ratioLoading % = (Pdc / Pac) × 100DC loadingPdc per inverter = Pdc / Number of InvertersPer-inverter DC loadingEngineering Notes
This tool reports ratio and loading figures against the inputs given — it does not model hourly irradiance, clipping energy loss, or revenue impact, all of which require production-simulation software with site-specific weather data. Treat the DC/AC ratio here as a design-check input to that analysis, not a substitute for it.
Manufacturer maximum DC input power, where entered, must come from the actual inverter datasheet for the model being used — this tool does not maintain or assume a database of inverter specifications.
FAQ
What is a 'good' DC/AC ratio?
There isn't a single universally correct number. A higher ratio increases energy harvest per inverter but increases clipping losses in high-irradiance periods; a lower ratio reduces clipping but under-utilises inverter capacity most of the time. The right ratio for a given project depends on irradiance profile, array orientation, inverter behaviour, local energy pricing, clipping tolerance and overall project economics — this calculator reports the ratio and loading, not a verdict on whether it's optimal.
What does 'clipping' actually mean?
When the array's DC output at a given moment exceeds the inverter's rated AC output capacity, the inverter caps its output at that AC limit — the excess DC power above the inverter's ceiling is not converted to AC and is lost for that moment. It typically happens for short periods around solar noon on clear days, not continuously.
Is DC/AC ratio the same as inverter loading percentage?
They describe the same underlying oversizing from two angles. DC/AC ratio is DC capacity divided by AC capacity, expressed as a ratio (e.g. 1.25). DC loading percentage expresses the same relationship as a percentage relative to the inverter's rated input (e.g. 125%). This tool reports both.
Why would anyone deliberately oversize the DC array relative to the inverter?
Because inverters rarely operate at their full rated capacity except briefly under peak irradiance — oversizing the DC side raises energy harvest during lower-irradiance hours (morning, evening, overcast) for a given inverter investment. The trade-off is calculated against clipping losses and the specific project's irradiance profile and economics, not assumed.