Solar Inverter Selection Scorecard for EPCs

A useful solar inverter selection scorecard starts with pass-or-fail engineering limits, then compares the surviving models on documented commercial and service criteria. This order prevents an attractive price, warranty headline or feature list from hiding a mismatch in voltage, current, phase, environment or grid requirements.

The framework below is for EPC procurement teams. It does not replace the project electrical design, the applicable DISCOM process, or an engineer’s review of the exact equipment and installation.

What should an EPC define before comparing inverters?

Define the project requirements before asking suppliers to score themselves. Record the array design envelope, AC connection, environmental conditions, operating objective, monitoring obligations, service expectations and commercial evaluation period. Without this baseline, every bidder can appear compliant by answering a different version of the project.

Create a project requirement sheet with these inputs:

Which criteria should be pass or fail?

Any criterion that can make the design unsafe, non-compliant or inoperable belongs in the pass-or-fail screen. Typical gates cover DC voltage and current, MPPT compatibility, AC output and phase, environmental limits, required grid evidence, protection interfaces and approved battery pairing where storage is included.

Use the exact proposed model, not a family name. Check at least:

The datasheet-reading guide explains how to separate maximum DC voltage, MPPT range and start-up voltage. Use the string-sizing calculator only as an initial screen, then verify the design against current module and inverter documents.

How should an EPC compare models that pass?

Score only the compliant models, using criteria and weights agreed before commercial bids are opened. A practical matrix can cover design fit, evidence quality, monitoring, service, warranty, supply execution and total cost. Add notes and document references beside every score so another reviewer can reproduce the decision.

Use a scale such as 0 = no acceptable evidence through 5 = fully meets the documented requirement. The scale is a procurement convention, not a product-performance claim. Define what each score means for each criterion before evaluation.

Do not award points for an adjective such as “smart,” “premium” or “AI-powered.” Score the observable function the project needs, the evidence that it exists, and who must provide the hardware or subscription.

How should efficiency and thermal behaviour be assessed?

Compare efficiency and thermal behaviour under stated conditions, not through one headline percentage. Record the efficiency metric, test basis, load range and any temperature or altitude derating that affects the site. Model expected energy with consistent assumptions if the difference matters to the procurement decision.

Maximum efficiency is not annual yield. Likewise, an operating temperature range does not prove that full output is available throughout that range. Request the applicable derating curve or manual and check whether the proposed mounting conditions preserve ventilation and required clearances.

If an energy-value comparison is included, keep the model inputs, loss assumptions and tariff basis in the decision file. Do not convert a datasheet difference into a lifetime saving without a reviewed energy model.

How should enclosure and site conditions be scored?

Match the documented enclosure and environmental limits to the surveyed installation, rather than declaring one IP rating universally sufficient. Rain exposure, dust, salt, direct sun, flooding risk, ventilation, altitude and maintenance access can change the mounting decision even when two products carry the same headline enclosure rating.

The IP65 versus IP66 guide explains what an ingress code does and does not establish. The EPC should also check the manual’s mounting orientation, clearances, connector requirements and any restrictions for corrosive environments. An IP code does not replace those installation instructions.

What should be checked in warranty and service terms?

Read the controlling warranty and service documents for the exact model. Compare when coverage starts, registration requirements, covered faults, remedy, exclusions, diagnostic steps and responsibility for labour, removal, transport and reinstallation. A duration shown in a brochure cannot answer those questions on its own.

The solar inverter warranty guide provides a document checklist. Retain the policy version with the purchase file instead of relying on a web-page summary that may later change.

How should monitoring and support be evaluated?

Test the monitoring and support workflow against the O&M team’s actual job. Confirm commissioning access, user roles, alarm detail, data export, connectivity hardware, subscription terms, firmware responsibilities and the route for technical escalation. A feature list is not a completed workflow test.

Ask the supplier to demonstrate a normal commissioning sequence and a fault escalation. Record whether extra gateways, SIMs, licences or mobile permissions are needed. Check what the client receives at handover and how access transfers if the original EPC no longer maintains the plant.

Support can be scored only from defined evidence. Named contacts, documented hours, escalation steps, training material and spare-parts commitments are more useful than an unqualified promise of “fast service.”

How should total cost affect inverter selection?

Compare total cost using the same scope, period and assumptions for every compliant model. Include installed acquisition cost, required accessories, commissioning, planned service, monitoring fees, expected downtime exposure, warranty responsibilities and replacement scenarios. Keep uncertain inputs visible instead of disguising them inside one confident total.

The inverter TCO worksheet provides the input structure. Run sensitivity cases for the inputs that can change the decision, such as service visits, downtime value, replacement timing or discount rate. A lower purchase price should win only if the comparable evidence supports the lower ownership cost or the client has explicitly prioritised capital cost.

A solar inverter selection scorecard template

Complete the pass-or-fail section first. Reject or resolve every failure before weighted scoring.

Technical gate

Weighted comparison

Have engineering approve the technical gate, O&M review monitoring and support, and procurement confirm the commercial comparison. Record the chosen model, rejected alternatives, open conditions and approvers in the decision note.

What should happen before a purchase order is released?

Before release, match the selected model and every promised accessory to the final design, quote and evidence file. Resolve qualifications, approve substitutions formally, attach the controlling warranty and define commissioning and handover records. The purchase order should not rely on a scorecard entry that the contract does not preserve.

The final file should include the approved single-line diagram, array calculations, exact SKU, current datasheet and manual, required compliance evidence, monitoring scope, warranty, service terms, delivery conditions and acceptance tests. Download current Qbits datasheets or request a model-specific technical review before procurement.

Sources checked 23 September 2026: the current Qbits datasheet library, Qbits product inventory and the linked Qbits technical guides. Product, certificate, warranty and support statements must be reconfirmed for the exact quoted model and project. Engineering, procurement and contract owners should approve the final scorecard before purchase.