| Comparable system scope | Usable energy, continuous and peak power, voltage, inverter inclusion, and number of stackable modules. | Compare quotations at the same usable kWh, power rating, and included accessories. Do not compare nominal capacity with usable capacity. | System datasheet, single-line diagram, itemized bill of materials, and a written list of included and excluded items. | A lower price may reflect less usable capacity, a separate inverter purchase, or missing installation components. |
| Cell chemistry and safety | Battery chemistry, module design, battery management system, thermal protection, and fault isolation. | For residential stationary storage, ask whether the system uses lithium iron phosphate (LFP) and request the exact safety and operating limits for the quoted model. | Cell and pack specifications, protection-system description, applicable test reports, and installation and emergency guidance. | Chemistry alone does not establish safety. Pack design, controls, system integration, and installation requirements also matter. |
| Cycle life and usable energy | Guaranteed energy throughput, cycle-life claim, depth of discharge, temperature, and end-of-life capacity. | Request cycle life under stated test conditions; a cycle-life figure without depth of discharge, temperature, and retained-capacity definition is not comparable. A 6,000-cycle claim, for example, should be checked against its test conditions and warranty. | Test report or detailed datasheet, warranty capacity curve, and written definition of end of life. | Real service life depends on operating conditions and warranty limits, not on the cycle count alone. |
| Warranty and service life | Warranty duration, throughput or cycle limit, capacity retention, exclusions, and remedy process. | Many residential storage offers are presented with around a 10-year warranty, but coverage varies considerably. Compare the actual warranty document rather than the headline duration. | Full warranty terms, claim procedure, authorized service arrangements, and confirmation of who pays labor and transport costs. | A long warranty can have limited value if throughput caps, installation conditions, or claim requirements are restrictive. |
| Factory quality controls | Incoming cell checks, module assembly controls, end-of-line testing, serial-number traceability, and corrective-action process. | Confirm that each finished unit receives documented electrical, communication, and protection-function checks before shipment. | Quality-management certificates with scope and validity, sample test records, inspection plan, and a factory-audit report. | Consistent production and traceability make defects easier to prevent, identify, and resolve. |
| Certifications and market access | Product and system certifications required in the destination market, plus grid or inverter approvals where applicable. | Verify that certificates cover the exact model, configuration, and intended market. Requirements differ by country and can change. | Complete certificates and test reports issued by the relevant bodies; confirm model numbers and certificate status independently. | Missing or mismatched approvals can delay customs clearance, installation, or grid connection. |
| Production and dispatch lead time | Production slot, pre-shipment inspection, export documentation, and time from order confirmation to dispatch. | As a planning estimate, allow roughly 4–8 weeks for production after specifications and payment terms are confirmed; request a current, order-specific schedule. | Written production milestones, capacity allocation, inspection date, and contractual consequences for missed milestones. | Lead times depend on order size, customization, component availability, and factory workload. |
| Freight and delivery time | Transport mode, route, shipping terms, port handling, customs clearance, and final delivery. | For ocean freight, a rough planning allowance of 3–6 weeks in transit may be useful, excluding production, port delays, customs, and inland delivery. Confirm the route-specific estimate. | Freight quotation, shipping schedule, insurance details, export documents, and a clear statement of responsibility under the chosen Incoterm. | The factory dispatch date is not the same as the date goods are available at the installation site. |
| Minimum order and flexibility | Minimum order quantity, sample-order terms, mixed-model orders, and spare-parts availability. | Check whether the factory accepts a pilot order and whether subsequent orders can use the same configuration and documented specifications. | Quotation at pilot and volume quantities, sample policy, spare-parts list, and change-control procedure. | Order flexibility can reduce inventory exposure and help validate product quality before scaling. |
| Total landed cost | Product price, inverter and accessories, packaging, freight, insurance, duties, taxes, commissioning, and expected service costs. | Calculate: equipment + shipping/insurance + import charges + installation/commissioning + expected maintenance or replacement costs. Use the same delivery term and tax assumptions for every quote. | Itemized pro forma invoice, freight and insurance quotations, tariff classification, and written clarification of excluded costs. | The purchase price alone does not show the cost of getting a compliant, operational system to the site. |
| Reliability and defect handling | Reported field failures, return procedure, replacement stock, response time, and root-cause analysis. | Ask for recent quality and warranty-claim data with clear reporting periods and definitions. Treat unsupported defect-rate claims cautiously. | Redacted quality summaries, corrective-action examples, service-level commitments, and replacement-part lead times. | Responsive, documented after-sales support can limit downtime and reduce the cost of a product issue. |
| Compatibility and monitoring | Inverter compatibility, communication protocols, monitoring access, firmware policy, and cybersecurity updates. | Confirm compatibility with the intended inverter and site design before ordering; identify any communication gateway or subscription requirement. | Compatibility list for the exact models, protocol documentation, monitoring terms, and firmware-update policy. | Compatibility gaps can require extra hardware, delay commissioning, or limit system visibility. |
