What earth resistance should I target?

The target depends on the installation and protection level; many industrial earths aim for a low single-digit ohm value or better, verified by test.

How often should earthing be re-tested?

At commissioning, annually, and after major electrical works.

Knowledge

Earth Resistance Testing: Why Sub-1 Ohm Matters for Your Factory

Sustech Engineering Team · 25/05/2026

What earth-resistance testing measures, why a low value matters, the method, and how often to test.

Why earth resistance matters

Your earthing system gives fault currents and lightning a safe path to ground. A high earth resistance means dangerous touch voltages, nuisance trips and poor protection. A low, stable earth resistance keeps people safe and equipment protected.

The Wenner method

Soil resistivity is measured with the Wenner four-pin method, and earth resistance with calibrated KYORITSU or FLUKE testers using the fall-of-potential technique. Results are documented against the design target for the installation and protection level.

How often to test

Earth resistance drifts with soil moisture, corrosion and changes on site. Test at commissioning and at least annually thereafter — and after any significant electrical works. We provide a documented report with remediation where values exceed target.

FAQ

What earth resistance should I target?: The target depends on the installation and protection level; many industrial earths aim for a low single-digit ohm value or better, verified by test.
How often should earthing be re-tested?: At commissioning, annually, and after major electrical works.