Where do the default numbers come from?
Charger profiles are derived from real EVFC project models. Default hardware and install costs assume EVFC PHOENIX 80A for L2 ($4,000 hardware + $5,050 install) and FALCÃO 240 for DCFC ($45,000 hardware + $113,750 install). All inputs are user-editable — the calculator works for any vendor's hardware.
How are demand charges calculated?
Demand charge = (kW per port × connectors) × ($/kW/mo) × 12 months. A 240 kW DCFC pulled from grid at full peak on a $15/kW/mo tariff incurs $43,200/year in demand charges alone — often more than the electricity bill itself. Battery-buffered clusters draw a fixed 83.1 kW from grid regardless of cluster size.
What battery pricing is used?
Na-ion is $700/kWh and SuperCap is $1,000/kWh. These are customer prices including EVFC margin — not wholesale cost. Pack size defaults to 150 kWh for a 2×FALCÃO 240 cluster and 50 kWh for an 8-port L2 cluster; both are user-editable.
What does 'battery sized per session burst' mean?
Per the patented XEYAR architecture (USPTO PPA Rev.12), Grid and Battery feed the shared DC bus simultaneously (additive). The battery covers the peak session burst, not a continuous full-power draw, because high C-rate batteries recharge between sessions from the 83.1 kW grid feed. This is why a 150 kWh pack can support a 480 kW cluster.
How is VPP revenue calculated?
Annual VPP = pack kWh × 0.5 (depth of discharge) × spread per kWh × cycles per 4h window × 264 operating days. Example: 150 kWh Na-ion × 0.5 × $0.16 × 10 cycles × 264 = $31,680/year. Na-ion supports 10 cycles per 4h window; SuperCap supports 8. Revenue activates once VPP market access is in place (NEXUS in 2026, then ERCOT, CAISO, AESO).
What financial assumptions does the model use?
LTV 75%, 7% interest rate, 10-year loan term, 20% effective tax rate, 7% discount rate for NPV, 10-year straight-line depreciation, 10%/year maintenance escalation, 15% working capital. Utilization ramps from Year 1 startup (50% of steady state for L2, 40% for DCFC) to full steady state by Year 4.
Can I model HPC, slow L1, or non-EVFC hardware?
Yes. Open Advanced Parameters in either ROI calculator. You can edit kW per port, charge time per session, energy per session, hardware cost, and install cost. The model works for any vendor's hardware from 7 kW workplace L2 up to 350+ kW HPC.
Why do the ROI calculators not ask for service voltage or phase?
Voltage and phase determine whether a project is electrically feasible — not how much money it makes once it's built. A 19.2 kW port produces the same revenue per kWh delivered whether it's wired on 240V single-phase or 208V three-phase. The ROI and Buffered calculators compute revenue, OpEx, demand charges, and debt service — all driven by kW per port, utilization, price, and tariff. Site-electrical questions (does this fit my panel? do I need an upgrade?) belong in the Load Management and Project Sizer tools above, which do use voltage and phase. If your installer's quote already includes the cost of running 480V three-phase service, just enter that number in the Install & Soft Costs field — the financial model takes it from there.
Can I trust these numbers for an actual investment decision?
Treat this calculator as an honest first look, not a final pro forma. Real numbers depend on site-specific factors: exact utility tariff, local incentives, site lease terms, traffic patterns. Use the Excel download as a starting point and get engineering and finance review before committing capital.
Why is the side-by-side buffered vs non-buffered comparison so dramatic for DCFC?
Two forces compound. First, a 480 kW cluster on a $15/kW/mo demand tariff burns $86,400/yr in demand charges — eliminated by a buffered system that draws only 83.1 kW. Second, the same battery earns VPP revenue ($31,680/yr for a 150 kWh Na-ion pack) when idle. Net swing: roughly +$100K/year, or +$640K over a 10-year hold. Payback compresses from ~44 months to ~23 months.
