BESS Cable Cost Estimator: AC vs DC Collection
Move the same power over the same route as three-phase AC or as DC, and see what each costs in cable, tray and terminations — and what each dissipates. The comparison is usually decided by current, and current is decided by the voltage you chose upstream.
How it works
- Split the power. Plant power is divided equally across the parallel circuits, giving the power each circuit carries.
- Find the current. AC current is P / (√3 · V · pf); DC current is P / V. This one step drives everything else, and it is why a 690 V AC circuit and a 1500 V DC circuit carrying identical power are not comparable pieces of copper.
- Count metres and ends. AC needs three conductors per circuit, DC two, each multiplied by the conductors per phase or pole and by 8% routing slack. Terminations are counted at both ends.
- Price it. Cable and installation are priced per metre, tray per metre of route, and terminations each.
- Estimate the loss. I²R at full power. Conductors in parallel each carry a share of the current, so the set dissipates I²R divided by their number.
A worked example
The tool's default case: 100 MW over a 120 m route in 8 parallel circuits, so 12,500 kW per circuit, at 690 V AC against 1500 V DC.
| AC at 690 V | DC at 1500 V | |
|---|---|---|
| Current per circuit | 10,459 A | 8,333 A |
| Cable | 3,110.4 m | 2,073.6 m |
| Terminations | 48 | 32 |
| Installed cost | $100,790 | $79,888 |
DC comes out $20,902 cheaper here, and almost all of that is the third conductor it does not need. But read the current row again before drawing a conclusion:10,459 A in one conductor is not a design, it is an arithmetic result. A real 690 V circuit at this power needs ten or more conductors per phase, and the moment you enter that, the cost and the loss both move. The tool is most useful once the conductor count is realistic for the ampacity you intend.
Assumptions, and where they stop holding
- One resistance for both sides.The same Ω/m is applied to AC and DC, so the comparison is at equal conductor size rather than at equal ampacity. Since the AC side carries more current at these voltages, a real design would put more copper there — which the cost column does not yet know about.
- DC resistance only.No skin effect, no proximity effect, no temperature correction, no harmonics. On large conductors at 50/60 Hz these raise the effective AC resistance, so the AC loss shown is optimistic.
- Loss is instantaneous, not energy.I²R at full power is the worst case, not an annual figure. Multiplying it by a duty-cycle factor is the next step, and this tool does not take it.
- The prices are yours, not the market's.Every rate is an editable input with a plausible starting value. They are not quotations, and they are not indexed to anything.
When not to use this
This is a comparison of two routings, not a cable schedule. It does not size a conductor: ampacity, installation method, grouping, ambient temperature and voltage drop all sit outside it, and any of them can decide the cross-section on their own. Use it early, to see which way the cost leans and by how much, then let the sizing calculation set the conductor and re-run this with those numbers.