Recommended Config
R 4,443
Year 1 Savings/unit
BESS Contribution
R 6,648
Demand charge savings
PV Trade-off Y1
-R 2,205
Premium vs Eskom
10-Year Cumulative
R 71,392
Per household total
Bulk Bill Reduction
35.1%
Per Nano-Grid unit
Two Savings Streams Analysis
Understanding PV Solar trade-off vs BESS demand charge reduction
Stream 1: PV Solar R/kWh Trade-off
PV Nano-Grid Tariff StartR 2.30/kWh
Eskom Bulk Tariff (Sun Hours)R 1.81/kWh
Year 1 Premium+R 0.49/kWh (+27%)
Escalation: PV @ CPI+1% (5%) vs Eskom @ 9%
Crossover: Year 7-8 (PV becomes cheaper)
Stream 2: BESS Peak Demand Reduction
Demand Charge RateR 44.32/kVA/month
25kWh BESS @ 0.5C12.5 kVA discharge
Annual BESS SavingsR 6,648/year
Calculation: 12.5 kVA x R44.32 x 12 months
Key: Immediate positive cash flow from Day 1
Pareto Frontier Analysis
45 configurations analyzed (9 PV sizes x 5 BESS sizes: 5-25kWh)
Key Insight: Maximum BESS capacity (25 kWh) consistently delivers highest savings due to demand charge reduction dominance. The PV contribution is initially negative but becomes positive after Year 7 as Eskom escalation (9%) outpaces PV escalation (5%).
Top Pareto Frontier Options by BESS Size
Comparing 5kWh to 25kWh BESS with 3.0kWp PV baseline
| BESS Size | BESS Savings | PV Trade-off | Net Year 1 | Bulk Reduction | 10-Year Value | Status |
|---|---|---|---|---|---|---|
| 3.0 kWp + 5 kWh | R 1,329 | -R 2,205 | -R 876 | -6.9% | R 12,891 | Net Loss Y1 |
| 3.0 kWp + 10 kWh | R 2,659 | -R 2,205 | R 454 | 3.6% | R 28,391 | - |
| 3.0 kWp + 15 kWh | R 3,988 | -R 2,205 | R 1,783 | 14.1% | R 43,891 | - |
| 3.0 kWp + 20 kWh | R 5,318 | -R 2,205 | R 3,113 | 24.6% | R 57,641 | - |
| 3.0 kWp + 25 kWh | R 6,648 | -R 2,205 | R 4,443 | 35.1% | R 71,392 | Recommended |
BESS Sizing Insight
Each 5kWh BESS increment adds R1,329/year in demand savings. The 5kWh minimum results in net loss due to PV premium.
Recommended Configuration
3.0 kWp + 25 kWh delivers 35.1% bulk bill reduction with R4,443/year Year 1 savings.
Key Findings
BESS demand charge savings (R44.32/kVA) dominate value proposition
PV at R2.30/kWh has 27% Year 1 premium vs Eskom bulk
Tariff crossover occurs at Year 7-8 (Eskom 9% vs PV 5%)
Minimum 10kWh BESS required for positive Year 1 cash flow
25kWh BESS delivers 35.1% bulk bill reduction per unit
10-year cumulative: R71,392 per household (3kWp+25kWh)
Fleet Deployment Impact
10,000 Household Deployment Scenario
Year 1 Fleet SavingsR 44.4M
Year 10 Fleet SavingsR 126.7M
10-Year CumulativeR 713.9M
Bulk Bill Reduction35.1%