Quick answer
DC-to-AC Ratio The DC-to-AC ratio, also called the inverter loading ratio (ILR), is a solar array’s total panel rating in DC watts divided by the inverter’s AC output rating.
A 9.6 kW array on a 7.6 kW inverter has a ratio of about 1.26. Ratios above 1.0 are normal, because rooftop panels rarely reach nameplate output; the cost is some clipping on the brightest hours.
Quick facts
The key facts about dc-to-ac ratio, with sources:
- Formula
- Array DC rating (STC) ÷ inverter AC rating
- Range studied by NREL
- 1.2 to 1.5, described as typical for new systems 1
- String inverter ceiling (example)
- SE7600H-US accepts up to 11,800 W DC on 7,600 VA: about 1.55 3
- Microinverter (example)
- 440 W panel on 295 VA IQ8PLUS: about 1.49 4
- Hybrid (example)
- Powerwall 3: 20 kW DC on 11.5 kW AC: about 1.74 5
- Trade-off
- Higher ratio = more off-peak output, more clipping at peak 2
- Where utilities use it
- Applications often ask for both kW DC and kW AC 7
Key takeaways
- The DC-to-AC ratio is panel watts divided by inverter AC watts.
- Ratios above 1.0 are normal. An NREL-led study calls 1.2 to 1.5 typical for new systems.
- A higher ratio adds output on most hours but clips more at midday.
- Every inverter data sheet sets a maximum DC input. Stay below it.
- Many utility size caps are in AC, so the ratio decides how big the array can be.
What the ratio tells you
A solar system has two sizes. The panel size is in kW DC, the label rating of all panels added up. The inverter size is in kW AC, the most power it can send to your home. The ratio compares the two.
A ratio of 1.0 means they match. A ratio of 1.3 means there is 30% more panel than inverter. Engineers call this the inverter loading ratio, or ILR. It decides how often you see inverter clipping.
How to calculate it from your proposal
- Find the panel count and the panel wattage (STC rating) on the proposal.
- Multiply them for the array’s DC size: 24 panels × 400 W = 9,600 W.
- Find the inverter’s rated AC output on its data sheet, not the proposal’s headline “system size.” For microinverters, multiply the continuous AC rating by the number of units.
- Divide DC by AC: 9,600 ÷ 7,600 ≈ 1.26.
- Check the result against the data sheet’s maximum DC input for that model.
If the proposal gives size only in kW DC, ask which figure the utility application uses. Some size limits are set in AC. See solar interconnection.
Why systems are built above 1.0
A panel’s DC rating is measured in lab conditions a roof rarely matches. Heat, dust, wiring losses and the sun’s angle all pull real output below the label. An inverter sized to the full DC rating would sit underused for most of the year.
Adding DC per unit of AC raises output in the morning, the afternoon and on cloudy days.
NREL researchers note that falling panel prices pushed designers toward higher ratios for this reason, while accepting more clipping at the peak 2.
A 2022 NREL-led study tested ratios of 1.2 to 1.5 as the typical range in new systems 1.
The cost is clipping. On bright, cool middays, available DC exceeds the AC limit and the inverter caps output. The same study found hourly models can understate that loss at higher ratios, by about 0–4% of yearly output across the systems it studied 1.
Ratio ceilings by inverter type, from real data sheets
| Product | AC rating | Maximum DC (or top common pairing) | Ratio ceiling |
|---|---|---|---|
| SolarEdge SE3800H-US to SE11400H-US (string) | 3,800–11,400 VA | 5,900–17,650 W @ 240 V 3 | about 1.55 |
| Enphase IQ8PLUS (micro) | 295 VA | 440 W 4 | about 1.49 |
| Enphase IQ8H-240 | 380 VA | 540 W 4 | about 1.42 |
| Tesla Powerwall 3 (hybrid) | 11.5 kW | 20 kW 5 | about 1.74 |
Example: three ways to pair the same roof
An example. The roof holds 24 panels of 400 W, or 9,600 W DC. The inverter AC ratings are from the SolarEdge HD-Wave sheet 3; the choice between them is the example.
| Inverter | Math | Ratio | What to expect |
|---|---|---|---|
| SE10000H-US (10,000 VA) | 9,600 ÷ 10,000 | 0.96 | Little or no clipping; inverter runs at low load most hours |
| SE7600H-US (7,600 VA) | 9,600 ÷ 7,600 | about 1.26 | Some clipping on bright, cool middays; within the 1.2–1.5 range NREL studied |
| SE6000H-US (6,000 VA) | 9,600 ÷ 6,000 | 1.60 | Above the HD-Wave ceiling of about 1.55, so outside the sheet’s DC limit |
The middle row is the kind of design most installers aim for. The last row is not a clipping choice. It breaks the data sheet limit, so a designer would not use it.
Where you find the ratio
Few proposals print the ratio. You usually work it out from two numbers: the system size in kW DC and the inverter model. Our proposal analyzer helps you find both.
Utility forms often ask for both sizes. Georgia Power’s application, for example, asks for total inverter nameplate in kW AC and total panel nameplate in kW DC 7. Your installer fills these in, but you can ask for a copy.
Design software reports it too. A production report may list “DC/AC ratio” or “ILR” next to the clipping loss.
Sources: [7]
Benefits of a well-chosen ratio
Ratio in a sensible range
Ratio too high or too low
- Too high: heavy clipping, and extra panels add little energy.
- Too high: may break the data sheet’s DC limit.
- Too low: you pay for inverter capacity the panels rarely use.
Limits of the ratio as a guide
The ratio is a rule of thumb, not a result. Two homes with the same ratio can clip very different amounts. Climate, roof angle and direction all change how often panels near their label.
It also ignores voltage. A string must stay inside the inverter’s voltage window. The SE7600H-US, for example, lists a 480 V maximum input 3. A design can pass the ratio test and still fail on voltage.
Models can be off. NREL found hourly models can understate clipping at high ratios 1.
What pushes the right ratio up or down
| Factor | Pushes ratio higher | Pushes ratio lower |
|---|---|---|
| Panel direction | East–west or split faces, which never peak together | One south face at a steep tilt |
| Climate | Hot or hazy summers that keep panels below their label | Cool, clear, high-sun sites where panels near their label |
| Battery | DC-coupled battery that can absorb some surplus | AC-coupled or no battery |
| Utility limits | Size capped in AC | Export rules that reward midday output |
| Future plans | — | Room left to add panels later |
How the ratio affects cost
We do not print prices. The ratio shapes cost in two ways. A smaller inverter for the same panels can cost less. More panels on the same inverter add cost per panel, but can lower cost per kWh up to a point.
Past the right ratio, each new panel adds less energy, so cost per kWh rises again. Ask for the yearly kWh at two or three ratios. Our cost by system size guide shows how size drives price.
How installers choose the ratio
A licensed installer does this design work. The usual order:
- They size the array in kW DC from your yearly kWh and roof space.
- They pick an inverter type for your shade and battery plans.
- They check the ratio against the data sheet’s DC limit and voltage window.
- They model output and clipping, ideally with subhourly data on high ratios.
- They check the AC size against your utility’s cap.
- They file the permit and utility application with both sizes listed.
Living with the ratio you have
After install, the ratio is fixed unless you change hardware. What you can do is watch output. A flat top at the inverter’s AC rating on clear days is clipping. That is expected on a ratio above 1.0.
If you add panels later, the ratio rises. The new total must still fit the inverter’s DC limit. Our adding panels page explains what that involves.
Red flags in a design
Ask questions, or get a second opinion from a licensed installer, if you see:
- A ratio above the maker’s maximum DC input.
- No clipping loss stated on a ratio above about 1.3.
- An inverter much larger than the array with no plan to add panels.
- Panels added later with no permit or utility notice.
Rules that set the limits
No code sets a target ratio. Two kinds of rule set the edges. First, the equipment listing. An inverter is certified to UL 1741 under the limits on its data sheet, such as the SE7600H-US’s 11,800 W maximum DC 3. Exceeding them is outside the listing.
Second, utility and state size limits. Georgia Power counts both kW AC and kW DC on its application, and caps its residential renewable program at 10 kW of peak capacity 7. Virginia sets a 25 kW residential net metering limit 8. Ask whether your cap is in AC or DC.
DC-to-AC ratio vs related sizing terms
| Term | What it means | Unit |
|---|---|---|
| DC-to-AC ratio (ILR) | Panel DC rating ÷ inverter AC rating | A plain number, such as 1.26 |
| System size (DC) | All panel ratings added up | kW DC |
| Inverter size (AC) | Inverter’s rated AC output | kW AC |
| Clipping loss | Energy lost when DC tops the AC limit | % of yearly kWh |
| System sizing | How big the array should be for your use | kW DC |
Misconceptions
- Myth A ratio above 1.0 means the inverter is undersized.
- Reality It is the normal design. A ratio of 1.0 or below usually means paying for inverter capacity the panels rarely use.
- Myth Higher is always better.
- Reality Each step up adds more clipping. Past the point your climate supports, extra panels add little energy.
- Myth The ratio is the same as system size.
- Reality System size is one number in kW. The ratio compares two sizes and has no unit.
AC size caps in SC, GA and VA
Where a cap is in AC, the ratio lets a home put more panels behind an inverter that fits the cap.
In South Carolina, Dominion Energy’s Solar Choice rider 9 and Duke Energy Carolinas’ Rider RSC 10 cap residential systems at 20 kW AC. Georgia Power limits its residential renewable program to 10 kW 7. Virginia’s residential net metering limit is 25 kW 8.
Size your system
- System size calculatorkW DC needed for your usage
- Panel count calculatorHow many panels fit that size
Questions about dc-to-ac ratio
What is a good DC-to-AC ratio for home solar?
An NREL-led study calls 1.2 to 1.5 the typical range for new systems. The right number depends on roof direction, climate and the inverter’s own DC limit. Ask your installer for the clipping loss your design assumes, and stay under the data sheet’s maximum.
Can I put more panels on my inverter?
Only up to the maximum DC input and voltage limits on the inverter’s data sheet. It usually needs a permit revision and a utility notice. A licensed installer should run the string and clipping checks. Adding panels raises your ratio and your clipping.
What is inverter loading ratio?
It is the same as the DC-to-AC ratio: panel DC rating divided by inverter AC rating. Engineers and NREL papers say ILR. Installers more often say DC-to-AC ratio. Both describe how much panel sits behind each watt of inverter.
Should my inverter be bigger than my solar array?
Rarely. An inverter larger than the array runs at low load most of the time. That is away from the 75% load where the CEC test puts most of its weight. Leave headroom only if you plan to add panels soon.
How do I find my system’s DC-to-AC ratio?
Multiply panel count by panel wattage for the DC size. Find the inverter’s AC rating on its data sheet. Divide the first by the second. For microinverters, multiply each unit’s continuous AC rating by the unit count first.
Is a 1.5 DC-to-AC ratio too high?
Not by itself. NREL studied 1.2 to 1.5 as typical, and some data sheets allow more. Whether it is too high depends on your climate and roof. Ask for the clipping loss and whether it was modelled with subhourly data.
Does the ratio affect my utility application?
Often, yes. Many applications ask for both kW DC and kW AC. Georgia Power’s form asks for both. Some size caps are in AC, such as the 20 kW AC caps at Dominion Energy South Carolina and Duke Energy Carolinas.
Why does a microinverter have a ratio too?
Each unit has its own AC limit. A 440 W panel on a 295 VA IQ8PLUS has a ratio of about 1.49. The system ratio is the total panel watts divided by the total of the units’ continuous AC ratings.
Sources
- Anderson et al., The Effect of Inverter Loading Ratio on Energy Estimate Bias: Preprint (NREL/CP-5K00-82812, 2022), retrieved .
- Perry, Muller and Anderson, Performance Comparison of Clipping Detection Techniques in AC Power Time Series: Preprint (NREL/CP-5K00-78954, 2021), retrieved .
- SolarEdge, Single Phase Inverter with HD-Wave Technology for North America data sheet (12/2020/V01, distributor-hosted copy), retrieved .
- Enphase Energy, IQ8 Series Microinverters data sheet (DSH-00378-5.0-EN-2026-07-13), retrieved .
- Tesla, Powerwall 3 Datasheet (2024), retrieved .
- Sandia National Laboratories, PV Performance Modeling Collaborative: CEC Inverter Test Protocol, retrieved .
- Georgia Power, Behind-the-Meter Interconnection Summary for Residential Customers (rev. 15 Aug 2025), retrieved .
- Code of Virginia §56-594 (net energy metering), retrieved .
- Dominion Energy South Carolina, Residential Solar Choice rider (Rider to Rate 5), retrieved .
- Duke Energy Carolinas (SC), Rider RSC Residential Solar Choice, retrieved .
Expert review
Written by the HyreSolar Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Ratios computed by dividing printed data-sheet limits; typical range and modelling bias from the 2022 NREL-led ILR paper; CEC weighting from Sandia; size caps from sc-local/facts.js, the Georgia Power summary and Va. Code §56-594. The sizing-factor table states direction of effect only.
Suggest a correction. We fix errors and say what changed.