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4 mm² or 6 mm² solar cable

Updated: October 2026

You already know the route, and someone has told you to buy 6 mm² to be safe. 4 mm or 6 mm solar cable is a voltage-drop decision, not a bigger number for its own sake. On a short domestic string the extra copper is often stiffness and cost. On a long run, 4 mm² can miss the drop target the installer is using. Titles that say 10 AWG and 6 mm² in the same line are not a measurement of either. It is not a calculator, and it is not a lab test. The rows are on the [solar cable comparison](/hub/electrical-equipment/solar-cable).

You already know the route, and someone has told you to buy 6 mm² to be safe. 4 mm or 6 mm solar cable is a voltage-drop decision, not a bigger number for its own sake.

Our top picks

Chedin Chedin solar extension, 1 m variant

Best overall

Chedin Chedin solar extension, 1 m variant
8.0/10about £6.99
View offer
iGreely iGreely 6 mm² solar extension, 3 m red and 3 m black

Rank 2

iGreely iGreely 6 mm² solar extension, 3 m red and 3 m black
8.6/10about £19.99
View offer
Tonton Tonton flat solar extension, 6 m, orange

Rank 3

Tonton Tonton flat solar extension, 6 m, orange
6.7/10about £26.64
View offer
On this page
  1. 1.What the extra copper changes
  2. 2.The 3 percent figure, and what it is not
  3. 3.10 AWG is not 6 mm²
  4. 4.How that shows up in this set

What the extra copper changes

Cross-section changes resistance and how the cable handles. It does not change the voltage class on the sheath, and it does not turn a 12 V accessory into array cable. A 6 mm² conductor has more copper than a 4 mm² conductor of the same length, so the voltage lost is smaller for the same current. Solvazcable reviewers said a thick pair is stiff. Ampacity and voltage drop are different tests. The MCS guide asks for cable behind the array rated at least 80 °C. The connector split is on MC4 or SAE solar cable. A bullet that disagrees with the title is on the solar cable buying guide.

The 3 percent figure, and what it is not

The MCS guide asks for DC voltage drop under 3 percent at standard test conditions, from the array to the inverter. It is not a result for any ASIN here. A two-metre shed link is a different sum from a 20 m garden run. Use 4 mm² when the run is short and the drop sum still sits inside that figure. Use 6 mm² when the run is long, strings are paralleled, or the 4 mm² sum is already over the target. Do not merge this with the AC limits people quote from BS 7671. Mating, once the size is chosen, is on how to connect a solar cable.
Chedin Chedin solar extension, 1 m variant

Testsieger

Chedin Chedin solar extension, 1 m variant
8.0/10about £6.99
View offer

10 AWG is not 6 mm²

Published conversion tables put 10 AWG at about 5.26 mm², not 6.0 mm². That figure is a published conversion, not a measurement of these reels. If a seller prints both, you do not know which label was the intent. Tonton’s title says 6 mm² and 10 AWG, 6 m, at £26.64. One UK review says 10 AWG is about 5 mm². Chedin’s parent line carries 10 AWG and 6 mm² while the 1 m bracket says 4 mm². iGreely’s title is about 6.0 mm² and 3 m, and its part number still says 10 AWG 10 ft.

How that shows up in this set

iGreely at £19.99 is the pair to open if the route wants about 6 mm² and about 3 m, at 4.7 from 2,201, with a part number that still says 10 AWG. Who should skip it is on best solar cable. Solvazcable’s 10 m title says 6 mm² at £35.99, and the bullet still says 3 m and 4 mm². The two ASINs share 4.5 from 112. LukAro is bare black 6 mm², 3 m, and the attribute says 18 V beside a 1,500 V DC bullet. IJIAMY’s 1 m pair does not state a cross-section.

Common questions

Is 4 mm² enough?
It is enough on a short run with one string when the voltage drop still sits inside the MCS guide figure of under 3 percent from array to inverter. A two-metre link to a shed is a different sum from a long garden run. This page has not calculated your string. Chedin’s 1 m and 4 m models put 4 mm² in the variant name, and their parent titles also say 10 AWG and 6 mm², so you still check the coil.
When is 6 mm² worth it?
When the run is long, when strings are paralleled, or when the 4 mm² drop sum is already over the target. Solvazcable reviewers called a thick pair stiff and hard to coil. It is not worth it as a habit on a one-metre plug-in lead, and it is not worth it if the bullet still describes 4 mm².
Does 10 AWG mean 6 mm²?
No. Published conversions put 10 AWG at about 5.26 mm², and 6 mm² is larger. That figure is a published conversion, not a test of these reels. Tonton prints both labels, and one UK review says the lead felt like 10 AWG rather than 6 mm². iGreely’s part number says 10 AWG 10 ft on a title of about 6 mm² and 3 m. Treat a double label as unresolved.
What voltage-drop figure are UK installers using?
The MCS installation guide asks for DC drop under 3 percent at standard test conditions from the array to the inverter, and for cable behind the array rated at least 80 °C. That is a guide figure, not a result for these ASINs. Do not replace it with the AC percentage you remember from a BS 7671 table. We have not run a drop calculation on any lead in this set, because the files do not contain your current or your route.
Why do reviews of a 4 mm² ASIN talk about 6 mm²?
Because Solvazcable’s 4 mm² / 5 m ASIN and its 6 mm² / 10 m ASIN share one pool of 4.5 from 112 reviews, and the stored UK texts are the same. A sentence about a thick 10 m core can be the other variant. Chedin’s parent title also stacks 4 mm² and 6 mm² under one star line of 4.8 from 1,105. Read the variant bracket and the bullet. If they disagree, the review cannot tell you which cable you will receive.

Related pages

Solar cable

Best solar cable: the row whose title matches the job

Solar cable buying guide: confirm the variant first

How to connect a solar cable: polarity, then click

MC4 or SAE solar cable: two families that do not mate

Sources

Public UK sources are listed below. Shelf prices and star lines are the amazon.co.uk figures checked on 21 October 2026.

  1. Tratos, BS EN 50618 (retrieved 21 October 2026)
  2. BASEC, solar photovoltaic cables (retrieved 21 October 2026)
  3. Prysmian PRYSUN datasheet (retrieved 21 October 2026)
  4. MCS installation guide (retrieved 21 October 2026)
  5. MIS 3002, solar PV systems (retrieved 21 October 2026)
  6. BEAMA technical bulletin, DC PV connectors (retrieved 21 October 2026)
  7. Stäubli, cross-mating of PV connectors (retrieved 21 October 2026)
  8. Approved Document P (2013) (retrieved 21 October 2026)