Battery Supported EV Charging ROI Calculator (beta)

This calculator helps you quickly compare the financial impact of upgrading your electrical supply versus installing a Battery Energy Storage System (BESS) to support EV charging.

It models energy flows, demand-charge reductions, solar utilisation, and lifetime costs to show where a BESS can unlock major savings or avoid expensive network upgrades.

Use it to explore different project scenarios, test tariff and load assumptions, and understand how battery performance over time affects whole-of-life economics. The tool is designed for e-bus depots, logistics fleets, shopping centres, industrial sites, public charging operators, and commercial property owners evaluating EV charging infrastructure.

Whether you’re early in planning or refining a business case, this calculator gives you a clear, data-driven picture of long-term costs, payback periods, and the comparative ROI of each pathway. It’s ideal for feasibility studies, internal approvals, investment analysis, and early discussions with networks, financiers, and technology partners.

By modelling both options side-by-side, you can make faster, more confident decisions about the smartest way to power high-capacity EV charging, without over-capitalising on supply upgrades.

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Scenario Presets

eTruck / eBus Depot – LFP

Large fleet depot using LFP storage. Moderate power, heavy overnight charging cycles.

eTruck / eBus Depot – LTO

High-cycle depot scenario with LTO chemistry, suited to extreme throughput and fast cycling.

Public Charging Site – LFP

Public fast-charging location with moderate utilisation and LFP-based energy shifting.

Public Charging Site – LTO

High-turnover public site with LTO storage enabling rapid cycling and demand charge mitigation.

Project Inputs

Enter project details to compare the financial outcome of installing battery storage to support EV charging loads versus upgrading the existing transformer and main switchboard. All values exclude GST for simplicity.

Supply Upgrade

Supply Upgrade Total Estimate Project Cost ($) Combined cost for supply upgrade including transformer & switchboard costs.

Battery Energy Storage System (BESS)

BESS Total Estimated Project Cost ($) Total cost including hardware, installation, switchboard works, civil & integration. BESS Energy Capacity (kWh) Total usable storage capacity of the battery. BESS Power Output (kW) Maximum discharge power from the BESS inverter; used to approximate the maximum reduction in EV-related demand charges. BESS Round-Trip Efficiency Overall charge and discharge efficiency. % of EV Charging Energy Supplied by BESS

BESS: 75% Grid: 25%

Ratio of EV charging energy served from battery storage rather than directly from grid. % of BESS Charging from Off-Peak

Off-Peak: 80% Peak: 20%

Share of BESS charging that occurs on off-peak tariffs. Remaining % charges during peak periods. % of BESS Charging from On-site Solar (%)

Solar: 30% Grid: 70%

Share of BESS charging energy supplied from on-site solar rather than the grid. BESS Cycles per Day Average equivalent full cycles per day (e.g. 1.0 = one full charge/discharge per day). BESS Annual Maintenance ($/yr) Ongoing maintenance, inspections, and service contracts. BESS Design Life (years) Expected operating life of the BESS for modelling purposes. BESS Annual Degradation Rate (%/yr) Average yearly reduction in usable capacity (typically 1–3% for LFP and 0.5-1% for LTO batteries).

EV Charging Load

Charger Power Rating (kW) Total connected EV charger capacity; also used to estimate potential maximum demand without load management. Daily Average EV Charging Energy (kWh/day) Average total energy dispensed per day across all EV chargers. EV Charging Efficiency (%) AC/DC conversion, cable and charger losses (used for indicative energy flows). % of EV Charging During Peak (%)

Peak: 70% Off-Peak: 30%

Share of EV load that naturally falls into peak periods before BESS smoothing. EV Charging Directly From Solar Surplus

Direct Solar: 15%

Approximate share of EV charging that coincides with on-site solar surplus before BESS stored solar (relevant to both scenarios).

Tariffs & Demand Charges

Peak Electricity Rate ($/kWh) Your delivered energy cost during peak periods. Off-Peak Electricity Rate ($/kWh) Your delivered energy cost during off-peak periods. Solar Feed-in Tariff ($/kWh) Value received per kWh exported to the grid; used as the opportunity cost of using solar to charge the BESS instead of exporting. Demand Charge Rate ($/kVA/day) Network demand charge based on maximum kVA demand. Maximum Demand Reduction via BESS (kVA) Approximate reduction in EV-related maximum demand achievable with the BESS and load management system. This is typically capped by the BESS power output (kW).

Finance Model

Upfront Loan Lease

Finance & Depreciation

Discount Rate for NPV (%) Discount rate used for simple NPV estimate of BESS savings.

Results

Results will be shown here after you click Calculate.

Battery Supported EV Charging ROI Calculator (beta)

Access the free Calculator

Project Inputs

Results

Annual Running Cost: BESS vs Supply Upgrade

Cumulative Savings: BESS vs Supply Upgrade

Energy Sourcing – Solar vs Grid (Year 1)