Why Undersized Cables Cost More Over Time

1. Energy Losses (I²R Losses)
   Smaller conductors have higher resistance. Every amp of current creates heat and wasted energy. Over time, these losses add up to thousands of pounds in extra electricity costs.

2. Voltage Drop Issues
   Long cable runs with undersized conductors cause voltage drops. Motors and sensitive equipment run below their rated voltage, reducing efficiency, increasing current draw, and shortening lifespan.

3. Safety Risks
   Undersized cables run hotter, accelerating insulation breakdown and increasing fire hazards. What looks like a small saving upfront can lead to expensive repairs and downtime later.

Real-World Examples

• Industrial Plant Analysis (DOE Study)
  In-plant distribution losses—often caused by undersized conductors—can range from 0.5% to 4% of total electricity use. For a plant consuming 10 GWh/year, that’s up to 400,000 kWh wasted annually, costing £48,000 at £0.12/kWh.

• Substation Feeder Upgrade Case
  A 20/0.4 kV network recorded 3,012,381 kWh in technical losses, equating to £140,000 per year. Upgrading cables and transformers significantly reduced losses and improved reliability.

The Real ROI of Proper Cable Sizing

Choosing a conductor one size larger than the minimum can:

• Cut voltage drop by 30–40%.
• Reduce energy losses by thousands of kWh annually.
• Pay back the extra copper cost in 1–3 years through energy savings alone.

Procurement Checklist

• Require compliance with NEC/IEC voltage drop limits (not just ampacity).
• Ask for a life-cycle cost analysis comparing minimum vs optimized sizing.
• Factor in future load growth—oversizing slightly now is cheaper than re-pulling cables later.

Key Takeaways

• The cheapest quote can become the most expensive over time.
• Undersized cables increase energy bills, maintenance costs, and safety risks.
• Proper sizing delivers fast ROI and long-term reliability.