What size cable for a 5000W inverter at 48V?
25mm² tinned marine battery cable (4 AWG), protected by a fuse we will size with you, for a 2 metre run.
Recommended cable
25mm² tinned marine battery cable
A 5000W inverter at 48V draws about 115.7A. The current rating is what decides the size here, not volt drop.
The answer, and how we got it
A 5000W inverter on a 48V system draws roughly 115.7A of DC current at full output, allowing for inverter efficiency. Over a 2 metre run, one way, that calls for 25mm² tinned cable.
| DC current at full output | 115.7A |
|---|---|
| Recommended cable | 25mm² (4 AWG) |
| Volt drop over 2m | 0.389V, 0.81% of nominal |
| Cable rating, derated | 170A |
| Has to carry | 116A |
| Conductor temperature assumed | 35°C |
| Fuse | see below |
We will not guess the fuse on this one. All 12 of our fuses at or above 145A are ruled out: no DC voltage rating recorded for this fuse, and this system is above the voltage we will assume one at. Ring us on 023 8045 5129 and we will sort the protection with you.
Worked for a single unbundled cable in a cabin, on the 10% general-circuit limit, with lead acid batteries. Note that the cable is sized to carry the fuse (116A), not just the load (115.7A): a fuse has to sit above the continuous current or it nuisance blows, and the cable has to carry the fuse or the fuse is not protecting it.
Your run is probably not exactly 2 metres
Length changes the answer more than anything else, and so does where the cable runs: a conductor at 60°C in an engine bay carries 15.7% more resistance than the same cable at 20°C.
Or go straight to a made-up 25mm² lead, cut, crimped with matched dies, heat shrunk and labelled.
Other inverter sizes
Same assumptions, different load.
BS EN ISO 13297:2021 requires that calculated volt drop does not exceed 10% of nominal voltage. For equipment vital to safety it requires that the equipment be supplied with the proper voltage to achieve its rated performance, and offers 3% as an acceptable figure for such equipment. An inverter feed is a general circuit, so this page works to 10%.
The derating we apply is ours, following ABYC E-11 practice. The manufacturer publishes a nominal current rating with no stated conditions. This is a design aid and not a design, and the installer remains responsible for the installation.
Figures generated from our live cable data and last reviewed 2 September 2026.