What is the DC/AC ratio in solar power?
The DC/AC ratio, also called inverter loading ratio, compares rated solar-panel capacity with rated inverter alternating-current output [S1]. An assumed 120 kWp array with 100 kW of inverter capacity has a ratio of 1.2. The ratio helps describe sizing; it does not state annual yield or the site's permitted export. Checked October 2026.
What does the DC/AC ratio mean for your site?
The DC/AC ratio is rated solar-array direct-current (DC) capacity divided by rated inverter alternating-current (AC) output capacity; it is also called inverter loading ratio [S1].
Why it matters for your site: it explains why a proposal can show more panel capacity than inverter capacity without those labels contradicting each other. It does not describe how much electricity your building will use.
Panel capacity is commonly expressed in kilowatts peak (kWp), a reference-condition rating. Inverter output is given in kilowatts (kW), a measure of power. For assumed capacities of 120 kWp and 100 kW AC: 120 ÷ 100 = 1.2. This illustration is sizing arithmetic, not a recommended ratio or a quote [S1].
Why might a designer specify more panel capacity?
Oversizing can increase annual generation for a given inverter size, while creating peak-time output limits. The model documentation identifies location, panel orientation and module cost as factors in that choice [S1].
Ask for alternative layouts with the same weather and loss assumptions. Request annual energy, clipping losses and the cost difference. Do not accept a claimed universal UK ratio in place of those calculations. Read inverter clipping for the lost-energy question.
How is this different from an export limit?
The ratio compares equipment ratings. An export limit concerns electricity crossing your grid connection. The Energy Networks Association describes G100 customer limitation schemes for controlling export or import [S2].
Keep panel rating, inverter rating and agreed export capacity as separate lines in the proposal. Neither a large inverter nor a particular ratio establishes permission to export.
Use commercial solar inverters explained and G100 export limitation explained for the wider design and connection questions.
Next step
Bring those separate ratings to the site check and get matched with an installer that covers your area.
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Common questions
What does a ratio above one describe?
It means rated panel DC capacity exceeds rated inverter AC capacity. It does not mean the panels produce their rated output continuously [S1].
Can the ratio be below one?
Yes mathematically: the inverter AC rating then exceeds panel DC capacity. Use the published capacity relationship and actual equipment ratings, rather than treating that layout as a yield forecast [S1].
Is there a single correct ratio for every UK business?
No. The model documentation identifies location, orientation and module cost as design factors. Ask for alternatives using your actual roof inputs [S1].
Should you divide by the export cap instead of inverter capacity?
No. Use rated inverter AC capacity. G100 concerns flows at the grid connection, a separate boundary from inverter conversion capacity [S1], [S2].
Does oversizing remove the need for a clipping estimate?
No. PVWatts limits modelled inverter output at its AC rating. Request the lost-energy estimate as well as annual output when comparing ratios [S1].
Ask about your site
Sources
- PVWatts system design and capacity calculation, National Laboratory of the Rockies,Last checked 19 October 2026
- G100 Issue 2 overview, Energy Networks Association,Last checked 19 October 2026