Solar Wire Size Calculator (Canada)

Free Canadian solar wire size calculator. Enter voltage, current, and run length to get the smallest AWG that stays within CSA C22.1 voltage drop limits for PV circuits.

Solar Wire Size Calculator

System voltage (V) Current (A) One-way length (ft) Max voltage drop (%)

Smallest wire that meets your spec

12 AWG

Drop at this size: 0.58 V (2.4%)

How to use this calculator

Enter four values:

System voltage — Canadian residential strings typically run at 250–600 V DC; off-grid cabin and RV systems use 12 V, 24 V or 48 V
Current — maximum amps the circuit will carry (panel Imp from the data sheet, or charge controller output rating)
One-way length — distance in feet from the array to the inverter or charge controller
Max voltage drop % — 3% is the typical CEC industry recommendation for DC strings, 2% is excellent

The calculator finds the smallest AWG that keeps drop within your target. Smaller wire is cheaper at Canadian copper prices and easier to terminate in standard MC4 connectors and CSA-listed combiner boxes.

Why wire sizing is critical for Canadian solar

Canadian arrays face two specific challenges that magnify the cost of undersized wire:

Long runs are common — many rural and cottage installations run from a ground-mount or barn-roof array to a house several hundred feet away
Cold pushes string voltage up but low irradiance keeps current modest — meaning the worst-case ampacity event (winter Voc spike) and worst-case voltage drop (summer Imp at full sun) happen at different times of year, both of which the design must handle

Going one AWG larger than the bare minimum is one of the cheapest performance upgrades on a Canadian DIY install — copper costs scale linearly, but loss reduction is exponential.

The voltage drop math

The calculator tries every standard AWG (14, 12, 10, 8, 6, 4, 2, 1/0) and computes the voltage drop for your inputs. It picks the smallest wire (highest AWG number) that meets your maximum drop percentage.

V_drop = 2 × Length(m) × Resistance(Ω/m) × Current(A)

The factor of 2 accounts for the round-trip — current flows out through the positive conductor and back through the negative. Resistance values come from CEC Table D3 and CSA C22.1 standard copper at 75°C operating temperature.

AWG	Ω/km @ 75°C
14	8.45
12	5.31
10	3.34
8	2.10
6	1.32
4	0.83
2	0.52
1/0	0.33

Each AWG step roughly drops resistance by 37%, which is why moving from 10 AWG to 8 AWG cuts marginal voltage drop on cabin and rural Canadian strings.

Typical Canadian PV wire sizes

Run length	5 A	10 A	20 A	30 A
10 ft	14 AWG	14 AWG	12 AWG	10 AWG
25 ft	12 AWG	10 AWG	8 AWG	6 AWG
50 ft	10 AWG	8 AWG	6 AWG	4 AWG
100 ft	8 AWG	6 AWG	4 AWG	2 AWG
200 ft	6 AWG	4 AWG	2 AWG	1/0

Assumes 3% max drop on a 24 V DC system. Higher string voltage cuts wire size dramatically — at 500 V DC the same kW carries about one-twentieth of the current at 24 V, and voltage drop scales with current squared.

Voltage drop versus ampacity — pick the larger size

CEC Section 4 sets ampacity with derating:

Ampacity — the wire must safely carry continuous current. Derate for ambient (CEC Table 5A), grouping in conduit (Table 5C), and the 1.25× continuous-duty factor that applies to PV source circuits per Rule 64-210
Voltage drop — the wire must keep the load above its minimum operating voltage

For long ground-mount or remote-cabin runs, voltage drop usually wins. For short, high-current battery-bank cables, ampacity wins. Always use the larger of the two requirements. This calculator handles voltage drop — confirm ampacity with CEC Table 2 (allowable ampacity for not more than three copper conductors in raceway) and apply derating.

CSA and CEC code references

CSA C22.1 (Canadian Electrical Code, 2024) — master Canadian electrical installation standard
CSA C22.2 No. 271 — PV-rated cable specification (RPV)
CEC Section 64 — solar photovoltaic systems
CEC Rule 8-102 — voltage drop allowances
CEC Rule 64-200 — cold-weather voltage adjustment for PV

NRCan and CanmetENERGY publish design guidance aligned with these standards. Your provincial AHJ (ESA in Ontario, Technical Safety BC, Régie du bâtiment in Québec, etc.) requires a CSA-stamped permit and inspection — the inspector will check both ampacity and voltage drop calculations as part of the rough-in inspection.

What it costs to get wire wrong in Canada

A typical 7 kW Canadian residential rooftop system installed in 2026 costs CAD 18,000–28,000 turnkey before incentives (Canada Greener Homes Grant data, NRCan benchmark studies, HomeStars and Solar Industry Magazine quotes). Annual generation is around 7,500–9,500 kWh depending on province. A persistent 2% voltage drop above the 3% target costs roughly 150 kWh/year — about CAD 22/year at the 2026 Canadian residential average of 14.5 cents/kWh. Across a 25-year warranty that’s around CAD 550.

Compare that to the cost of upsizing a 100 ft run from 8 AWG to 6 AWG — about CAD 75–110 in materials at Canadian wholesaler prices. Upsizing pays back many times over.

Solar voltage drop calculator — full CEC voltage drop calculation
Solar panel tilt calculator — Canadian latitude and snow-shedding tilt
Solar panel orientation calculator — south versus east-west yield
Solar charge time calculator — battery charging from PV

For grid-tied systems, your provincial utility (Hydro One, BC Hydro, Hydro-Québec etc.) requires a permit-stamped electrical drawing and CSA-certified installer sign-off before energizing. Always demand a written cable-sizing calculation as part of the design pack — it protects you on both warranty and inspection day.

Frequently asked questions

What does the Canadian Electrical Code require for PV wire sizing?

CSA C22.1 (the Canadian Electrical Code, 2024 edition) Section 64 covers solar PV systems and requires conductors to be sized for both ampacity per Section 4 (Tables 1–4) and voltage drop. The CEC recommends keeping total drop from source to point of use below 5%, with industry practice being 3% on the DC side and 2% on AC side. PV source-circuit conductors must also be rated for at least 90°C and be sunlight-resistant when run in or on roofs (typically USE-2 or RPV-rated cable).

Which wire types are approved for solar in Canada?

For exposed DC PV strings, use RPV (Rated PV) or USE-2 cable approved to CSA C22.2 No. 271. Inside conduit, RWU90 or T90 stranded copper is common for PV combiner-to-inverter runs. For AC-side and battery-bank runs indoors, RW90 or NMD90 are typical. Always confirm the conductor type is listed in the CEC Table 19 for the application — a CSA-certified electrician will specify this on the permit drawings.

Do I size for ampacity or voltage drop?

Both — pick the larger of the two requirements. CEC Section 4 sets ampacity (with derating for ambient temperature, grouping and continuous duty per Section 8), and CEC Rule 8-102 requires voltage drop within design limits. For long runs from a remote array to the inverter, voltage drop usually drives a larger conductor than ampacity alone would require. For short, high-current battery cables, ampacity wins. This calculator handles voltage drop — confirm ampacity with CEC Table 1 or 2.

What about cold-weather considerations in Canada?

Cold improves cable performance — copper resistance falls about 0.4% per °C below 25°C, so a string sized at 25°C will have less drop on a -20°C January morning. The opposite is more important: PV string voltage rises sharply in cold weather (CEC Rule 64-200 cold-temperature adjustment), so size your cable for hot-weather current and verify the open-circuit voltage stays within the inverter's MPPT and disconnect ratings using the panel's published Voc temperature coefficient.

Solar Wire Size Calculator (Canada)