| 1 | Compare the Correct Price Basis | The 2024 global average lithium-ion battery pack price was reported at $115/kWh. | Pack pricing does not normally include the enclosure, battery-management system, inverter, thermal management, installation, controls, transport, taxes, or project development. | Request separate prices for the battery pack, complete battery energy-storage system, installation, commissioning, and long-term service. |
| 2 | Size Energy and Power Separately | Energy capacity is measured in kWh or MWh; power capacity is measured in kW or MW. | A system rated at 1 MW / 4 MWh can theoretically discharge at 1 MW for approximately four hours before accounting for operating limits and losses. | Define the required discharge duration, peak load, ramp rate, and minimum state of charge before comparing offers. |
| 3 | Use Usable Capacity, Not Nameplate Capacity | Commercial lithium-ion systems commonly specify an operating depth of discharge around 80%–95%, depending on the product and warranty. | Usable energy = Nameplate energy × permitted depth of discharge A 100 kWh system operated at 90% depth of discharge provides approximately 90 kWh before conversion losses. | Make suppliers state guaranteed usable kWh at the beginning and end of the warranty period. |
| 4 | Check Round-Trip Efficiency | A practical planning range for many lithium-ion storage systems is approximately 85%–95% AC round-trip efficiency, depending on system design, operating point, and auxiliary consumption. | Delivered energy = Charged energy × round-trip efficiency At 90% efficiency, 100 kWh charged produces approximately 90 kWh delivered. | Compare measured AC-to-AC efficiency under the intended load profile, not only the cell-level figure. |
| 5 | Evaluate Cycle Life and Warranty Throughput | Lithium-ion storage products may be rated for roughly 3,000–8,000 equivalent full cycles, depending on chemistry, temperature, operating window, and power level. | Equivalent full cycles convert partial cycles into full-cycle equivalents: two 50% cycles equal approximately one equivalent full cycle. | Ask for guaranteed retained capacity, maximum annual throughput, cycle limits, and the test conditions used to determine the rating. |
| 6 | Model Capacity Degradation | A planning assumption of approximately 1%–3% annual capacity loss is commonly used for preliminary financial models, but actual degradation varies significantly. | Degradation is influenced by temperature, average state of charge, depth of discharge, charge rate, discharge rate, and calendar age. | Include a year-by-year usable-capacity curve and require performance guarantees at the project’s expected operating profile. |
| 7 | Control Thermal Conditions | Many lithium-ion systems are designed for operation near 15°C–30°C for favorable performance, while wider ambient ranges may require active heating or cooling. | High temperatures generally accelerate aging; low temperatures can reduce available power and may restrict charging. | Verify the operating temperature range, auxiliary cooling consumption, fire-safety design, ventilation requirements, and climate-specific derating. |
| 8 | Account for Balance-of-System Costs | The battery pack is only one component of a complete project. Total installed cost can also include power conversion, protection, controls, civil works, cabling, grid studies, installation, commissioning, and software. | A low pack price does not necessarily mean a low installed cost or low lifetime cost. | Compare total cost of ownership using the same scope, currency, delivery terms, installation conditions, and tax assumptions. |
| 9 | Calculate Lifetime Cost per Delivered kWh | Illustrative example: 100 kWh nameplate capacity, 90% usable depth of discharge, 90% round-trip efficiency, 6,000 equivalent full cycles, and a $115/kWh pack cost. | Initial pack cost = 100 kWh × $115/kWh = $11,500 Lifetime delivered energy = 100 × 0.90 × 6,000 × 0.90 = 486,000 kWh Pack-only lifetime cost = $11,500 ÷ 486,000 = approximately $0.024/kWh | Treat the result as a pack-only illustration. Add replacement parts, service, financing, energy losses, degradation, augmentation, installation, and recycling costs for a project-level calculation. |
| 10 | Verify Safety, Compliance, and Serviceability | Safety requirements vary by jurisdiction and application. Projects may require documented testing for battery safety, electromagnetic compatibility, transport, fire protection, grid interconnection, and environmental conditions. | Certification, monitoring, isolation, emergency shutdown, cell-level protection, event logging, and clear maintenance procedures affect both risk and operating cost. | Obtain the full compliance package, hazard analysis, emergency response procedures, spare-parts plan, software-update policy, and local technical support commitments. |