The sunny spot is over there. Your RV is parked under the trees. Now you need to get power from one to the other without buying the wrong cable.
That sounds like a small job until you start shopping. One listing says 12 AWG. Another says 10 AWG. Some cables come in pairs, some come individually, and a few have ends that look almost—but not quite—like the ones on your equipment.
I’d start with your setup and a tape measure. Once we know what you’re connecting, how much current it carries, and how far the cable must travel, the choices become easier to narrow down.
The right solar cable size depends on circuit current, cable length, allowable voltage drop, installation conditions, and the ratings of every connection. You cannot choose it reliably from panel wattage alone. A cable must both carry the required current safely and deliver power with acceptable loss.
This guide focuses on the DC wiring used with RV solar, small off-grid systems, and portable power stations. We’ll work through the measurements, compare cable types you can actually buy, and explain where a thicker wire helps.
First, which part of the system are you wiring?
Before asking whether you need 10 AWG or 12 AWG, identify the two things the cable connects. The lead between your panels and controller does a different job from the lead between your controller and battery.
A portable power station usually has its solar charge controller built in. A separate RV house-battery system normally has an external controller. That changes which cables belong in your shopping cart.
Solar connector ↔ solar connector
More reach for a compatible PV connection.Solar connector → approved terminal end
For a controller with suitable wire terminals.Controller terminal → battery lug
A separately sized, appropriately protected circuit.I would put battery-to-inverter wiring in a separate category again. An inverter can draw much more current than a small panel circuit. A solar extension cable is not an automatic substitute for a properly sized inverter cable.
If your setup is still taking shape, our solar charge-controller sizing guide explains the equipment between the panels and battery.
What do 10 AWG, 12 AWG, and square millimeters mean?
AWG stands for American Wire Gauge. In the sizes we’re discussing, a smaller AWG number means a larger conductor. So 10 AWG has more conductor cross-sectional area than 12 AWG, and 8 AWG has more than 10 AWG.
That number describes the conductor, not the outside thickness of its insulation. Two cables that look equally chunky can contain different amounts of metal.
You may also see sizes in square millimeters, written as mm². This is the conductor’s cross-sectional area. For orientation, 12 AWG is about 3.31 mm², 10 AWG is about 5.26 mm², and 8 AWG is about 8.36 mm². A metric 6 mm² cable is therefore not exactly the same size as 10 AWG.
For otherwise comparable copper conductors, increasing that area reduces resistance. Less resistance means less voltage drop at the same current and distance.
It does not mean every 10 AWG product has one universal current rating. The insulation, temperature, installation method, connector contacts, and terminations also matter. When comparing products, I’d read the complete cable assembly’s specifications rather than stop at the gauge.
Gather these four details before choosing a cable
You don’t need to memorize an electrical textbook. You do need the right information from your labels and manuals.
1. The panel arrangement and electrical ratings
Write down how many panels you have and whether they are connected in series, parallel, or separate inputs.
For estimating operating losses, the useful panel ratings are Vmp, voltage at maximum power, and Imp, current at maximum power. Actual values change with conditions, but these give you a stated operating reference.
You also need Voc, open-circuit voltage, and Isc, short-circuit current, for equipment limits and circuit design. The final conductor and protection selection must account for applicable PV current allowances, temperature adjustments, installation rules, and manufacturer instructions. A low reading on a cloudy day is not your circuit’s design current.
A panel sold as “12V” does not necessarily operate at 12V. Use its electrical specifications, not just the nominal battery-system label in the product title.
2. The receiving equipment
Record the controller or power station model, its solar-input limits, and its approved connection method. For a controller with screw terminals, check the accepted conductor sizes and termination instructions too.
A thicker cable cannot fix an array that exceeds the equipment’s maximum voltage. An adapter that fits cannot fix that problem either.
3. The actual cable route
Measure the path the wire will follow, including the route around furniture, through an approved entry point, or along the roof. Leave appropriate service slack without buying a much longer run just because it might be useful someday.
Include existing panel leads and adapters when evaluating the full circuit’s losses. If one section is thinner, calculate its resistance separately rather than treating the whole route as the largest cable size.
4. The installation environment
Will the cable sit in sunlight, pass through conduit, share a bundle with other conductors, or enter a hot compartment? Does it need protection against abrasion, movement, moisture, or other exposure?
Those details affect selection. “It reaches” and “the connector clicks” are useful observations, but neither finishes the job.
Measure the distance there and back
This is the part I would check twice because it is easy to enter the wrong length into a calculator.
If your panels are 25 feet from the controller along the cable route, the positive conductor travels approximately 25 feet and the negative conductor travels approximately 25 feet. Together, that is a 50-foot conductor loop.
You would buy two suitable 25-foot single-conductor leads for that extension, or a matched pair containing one of each. You would not need two 50-foot leads just because the resistance calculation uses 50 feet.
A two-conductor cable has both paths inside one outer jacket. The electrical loop still includes both conductors, even though you only handle one cable assembly.
Different calculators ask for different inputs. Some want one-way distance; others want total conductor length. Read that label before using the answer. Accidentally doubling the distance twice can push you toward unnecessarily heavy cable.
Check safe current capacity and voltage drop separately
Think of these as two questions the cable needs to answer.
First: can this complete circuit safely carry its design current? That involves conductor ampacity, which means allowable current under the installation conditions, along with connector ratings, terminal limits, and overcurrent protection.
Second: will too much voltage be lost before the power reaches the equipment? That depends on current and resistance throughout the positive and negative paths.
A cable can pass the first check and still waste more power than you want on a long run. A voltage-drop calculator can also give you a small enough number without checking a connector’s rating or an installation rule.
For the examples below, I’ll use 3% as a comparison target. It is a design choice for illustrating loss, not a universal safety limit or permission to ignore equipment instructions. A particular charging circuit may need a tighter target.
What does voltage drop actually cost you?
Let’s picture a hypothetical panel operating at 20V and 10A. That is 200W at that operating point. Its cable route to the input is 25 feet each way.
Using an approximate 10 AWG copper resistance of 0.001 ohm per foot, the 50-foot loop has about 0.05 ohm of resistance.
- Voltage lost: 10A × 0.05 ohm = 0.5V.
- Percentage lost: 0.5V ÷ 20V × 100 = 2.5%.
- Power lost in the wire: 10A × 0.5V = 5W.
At that assumed operating point, about 195W remains after the modeled wire loss. That is not a promise of 195W reaching the battery: connectors, adapters, charging electronics, and changing sunlight can introduce other losses or limits.
The comparison below uses rounded copper-resistance values from Victron’s AWG conversion and resistance chart. Actual cable construction and operating temperature affect resistance, so use the selected cable’s data for final design.
| Cable and one-way route | Voltage drop | Wire power loss |
|---|---|---|
| 12 AWG · 25 ft | 0.80V · 4.0% | 8.0W |
| 10 AWG · 25 ft | 0.50V · 2.5% | 5.0W |
| 8 AWG · 25 ft | 0.315V · 1.6% | 3.15W |
| 12 AWG · 50 ft | 1.60V · 8.0% | 16.0W |
| 10 AWG · 50 ft | 1.00V · 5.0% | 10.0W |
| 8 AWG · 50 ft | 0.63V · 3.2% | 6.3W |
Assumptions: equal-length outgoing and return conductors; rounded resistance of 0.0016, 0.0010, and 0.00063 ohm/ft for 12, 10, and 8 AWG respectively. Values exclude connector resistance and temperature corrections. Results are rounded independently.
For the 25-foot example, moving from 12 AWG to 10 AWG reduces modeled wire loss from 4% to 2.5%. Extend the same 10 AWG route to 50 feet each way, and its loss becomes 5%.
That is why “10 AWG is fine for solar” is not a complete answer. It may be a reasonable size to evaluate for one arrangement and a poor fit for another.
If you want to check your own numbers, the basic formula is voltage drop = current × total loop resistance. For mixed cable sizes, add each section’s resistance before multiplying by current. Then divide the voltage drop by the operating voltage to find the percentage.
Series and parallel connections change what the cable carries
Suppose you have two matching panels, each operating at 20V and 10A under the example conditions. Together, they represent 400W before losses.
In series, the example array operates at about 40V and 10A. In parallel, it operates at about 20V and 20A. The common cable leaving the parallel connection carries the combined current.
Using the same 25-foot, 10 AWG cable pair from our earlier example gives us this comparison.
40V × 10A = 400W
1.25% of the example array power
20V × 20A = 400W
5% of the example array power
Doubling current produces four times the wire heating loss in the same resistance because that loss follows current squared: I²R.
However, I would never change your panels to series just to improve the cable calculation without checking the receiving equipment. Series increases voltage, including open-circuit voltage, which can rise further in cold weather. Parallel increases combined current and can change protection requirements.
The arrangement must fit the controller or power station first. Our series versus parallel wiring guide explains those checks. Here, the important point is to calculate the cable for the arrangement you actually intend to use.
The battery-side cable needs its own calculation
One detail often surprises people: an MPPT controller can receive a relatively low current from a higher-voltage array and send a higher charging current to a lower-voltage battery.
Imagine 400W arriving at a controller at 40V and 10A. If that controller delivers 95% of the incoming power in this example, 380W reaches its battery-side output. At a 14V charging voltage, that corresponds to about 27.1A.
I would therefore size the controller-to-battery circuit from the controller’s specified output, the battery-system requirements, the route, and the applicable design allowances—not from the panel-side 10A in that example.
A short, serviceable battery-side route is worth planning. A voltage drop that seems small on a higher-voltage PV circuit can be more significant when the controller is trying to charge a low-voltage battery accurately.
Keep the controller within its permitted mounting environment and clearances. “Close to the battery” is a layout goal, not permission to place it somewhere prohibited by either device’s manual.
Which cable products would I compare for your setup?
Now we can shop by the job. These are examples from our catalog, not a claim that every cable below works with every panel or controller.
For a matched pair of solar extensions
The RICH SOLAR 10 AWG extension pair includes red and black leads with solar connectors on both ends. The available lengths make it a useful option to evaluate when you need additional reach on a compatible PV circuit.
I would select the shortest practical route after checking voltage drop and connection compatibility. The existence of a 100-foot option does not mean a 100-foot run is efficient or suitable for every small panel setup.
For individual 12 AWG or 10 AWG extensions
Our Renogy 20-foot 12 AWG extension and 20-foot 10 AWG extension provide two sizes to compare for an otherwise suitable connection.
Watch the quantity: Renogy’s manufacturer listing identifies the extension as one cable. If you need to extend both positive and negative conductors, make sure your order provides both paths. Two connectors on one lead do not make it a two-wire pair.
For solar panels feeding a controller’s wire terminals
The RICH SOLAR 10 AWG panel-to-controller pair has solar connectors at the panel end and exposed wire ends at the controller end.
The manufacturer’s specifications list a 30A rated current and lengths of 10, 20, or 30 feet. Treat that rating as a limit to check alongside installation allowances—not a reason to assume the assembly suits any circuit with a reading below 30A.
Confirm that the controller accepts the conductor size and termination method. Do not trim away strands to make a wire fit. If the controller needs a different size or approved termination, choose the correct assembly for it.
For a controller-to-battery connection
The RICH SOLAR controller-to-battery cable pair uses battery ring terminals and controller-side wire ends, with 8 AWG and 10 AWG options.
I would check the selected assembly’s permitted current, lug dimensions, length, and controller compatibility before recommending it. A listing that offers 8 AWG does not automatically establish suitability for every 40A or 60A controller.
This circuit also needs appropriate battery-side overcurrent protection. A pre-terminated cable pair does not necessarily include the correctly rated fuse, holder, disconnect, or other installation hardware.
For a compatible Jackery portable setup
The Jackery DC Extension Cable for Solar Panel is a different style of assembly from the separate positive and negative PV leads above. Jackery lists this model as a 16.4-foot extension; see its official cable specifications.
Match the exact panel, station, connector, and approved extension arrangement. Do not assume every SolarSaga generation uses the same connection, or that several extensions can be chained together without checking the manufacturer’s limits.
If you are connecting a different brand of panel to a power station, our solar-panel compatibility guide covers the voltage, current, polarity, and adapter questions.
Connectors and protection are part of the cable decision
A large conductor does not upgrade a smaller connector attached to it. The circuit still has to respect each component’s limits, including adapters and any branch connectors used to combine panels.
Also, “MC4” is often used loosely in listings. A similar appearance does not prove two connector halves are approved to mate. Identify the actual connector manufacturer and compatible product family. Stäubli, the manufacturer of original MC4 connectors, explains the problem in its guidance on avoiding connector cross-mating.
This does not mean every component in your system must carry one brand name. It means the specific mating connectors need documented compatibility. If a product listing does not identify them clearly enough, ask before connecting them.
For a fixed installation, conductor sizing and fuse or breaker selection belong together. PV strings may require protection based on the array configuration and possible reverse current. Battery circuits need protection suitable for the cable and the battery’s available fault current. A generic fuse chosen only from panel wattage is not a complete design.
For a deeper explanation of cable selection, terminations, and DC protection, Victron’s Wiring Unlimited guide is a useful technical reference.
I’d have the installer confirm those details rather than fill the cart with a cable, a random inline fuse, and a handful of adapters that happen to fit. Use the equipment’s shutdown procedure when making connections, and do not unplug PV connectors under load.
Before ordering, walk the route one more time
This is where I would stand beside the equipment with you and make sure the plan works outside the spreadsheet.
- Count every cable: include the positive and negative paths, any panel interconnections, and the final lead into the controller or station.
- Check every end: solar connectors, controller terminals, battery lugs, and power-station plugs each have their own requirements.
- Check the route: avoid pinching a lead in a door, dragging it across a sharp edge, or creating a trip hazard through the campsite.
- Check the installation parts: suitable supports, roof-entry hardware, protection devices, and weather sealing may be separate purchases.
- Check tomorrow’s plan: adding panels in parallel changes the current in the shared cable. Recalculate before expanding.
If reaching the sunny spot requires an awkward route, moving the panels or equipment may be a better first adjustment than buying the longest cable available. Our portable versus roof-mounted RV solar guide helps you compare those layout tradeoffs.
Common solar-cable questions
Is 10 AWG better than 12 AWG for solar panels?
For comparable copper cable at the same current and length, 10 AWG has less resistance. Whether you need it depends on the complete circuit. Check safe current capacity, voltage drop, connector ratings, installation conditions, and terminal compatibility before choosing.
What cable size do I need for a 200W solar panel?
Start with the panel’s actual voltage and current ratings and the cable route. A hypothetical 200W panel operating at 20V carries 10A; one operating at 40V carries 5A. Those create different losses in the same wire, even though both are labeled 200W. Wattage alone is insufficient.
How far can I run a solar extension cable?
There is no universal distance. The answer depends on voltage, current, conductor size, permitted loss, connector limits, and the equipment’s approved configuration. A cable available in a long length is not automatically appropriate for your system at that length.
Does a 25-foot cable pair give me 50 feet of reach?
Normally, a pair containing two 25-foot single-conductor leads gives approximately 25 feet of extension reach. The two conductors total 50 feet for the resistance calculation. Confirm how the seller describes the selected package.
Can I use an ordinary household extension cord?
Do not substitute a household AC extension cord assembly for an approved PV cable and connector arrangement. Cable construction, environmental suitability, voltage ratings, and connections must fit the DC application. AC extension cords used at a power station’s outlets are a separate subject.
Will thicker wire make my panels produce more power?
It can reduce loss in the wire, allowing more of the available power to reach the input. It cannot create more sunlight, remove shade, increase a station’s input limit, or correct an incompatible panel arrangement.
Choose the connection first, then the size
The goal is simple: get the available solar power to your equipment through a suitable, serviceable connection.
Start with the two devices you are connecting. Record the electrical ratings. Measure the route. Check current capacity and voltage drop separately. Then select the cable ends, protection, and installation parts that complete that specific circuit.
You can compare the available assemblies in our cables and connectors collection. If you need help narrowing them down, send us the panel and controller or power-station model numbers, panel quantity and arrangement, and your one-way cable distance.
With those details, we can help you work toward a cable choice that fits your setup—and avoid discovering at the campsite that you bought the wrong ends, the wrong quantity, or more cable loss than you expected.
