ESS Supplier RFQ Checklist: 12 Items to Specify
The fastest way to compare two C&I battery storage quotes is to make both suppliers answer the same 12 questions in writing. Without them, a lower price usually means a different battery, a narrower warranty or missing documentation. This checklist is what we ask manufacturing partners to confirm before we pass a quotation to a buyer.
It applies to 50–200 kWh modular LFP cabinets used for peak shaving, backup power and solar self-consumption. It is written for integrators, EPCs, distributors and facility owners preparing a request for quotation — not for utility-scale projects.
This page is a field definition sheet, not a questionnaire. Each of the 12 items is written as a field with a required unit, a required basis and a required document, so that the answers can be entered into the quote comparison worksheet and ranked on the same basis. Five of the twelve items become a column in that worksheet. The other seven cannot be priced — they are pass/fail gates that decide whether a bid is eligible to be ranked at all.
The 12 fields, with the answer format each one needs
A field is not usable unless the supplier knows what unit, what test basis and what document you will accept. The right-hand column says where the answer lands in the worksheet: column means it is priced, gate means it must be cleared before the quote is comparable.
| # | Field | What to require in writing | Lands in the worksheet as |
|---|---|---|---|
| 1 | Cell chemistry and cell maker | Chemistry (LFP or other) plus the cell manufacturer and model. A system maker that rebadges cells should name the cell it ships. | Gate — document check |
| 2 | Capacity and depth of discharge | Two separate numbers: nameplate kWh, and depth of discharge at the warranty condition. Not a combined "usable capacity" claim without the DoD behind it. | Column — nameplate kWh + DoD %, which produce usable kWh |
| 3 | Rated power and peak duration | Continuous kW at a stated ambient temperature, plus the kW and duration of any short-term peak. State whether the PCS is in the same enclosure or supplied separately. | Column — PCS included (yes / no) |
| 4 | DC voltage and topology | Nominal DC voltage range and whether the battery is AC-coupled or DC-coupled to the existing inverter. | Gate — compatibility with the site |
| 5 | Cycle life with conditions | Cycle count at a stated DoD, C-rate and ambient temperature, plus end-of-test capacity retention. "6,000 cycles" without those three conditions is not a specification. | Gate — feeds the warranty basis |
| 6 | Warranty basis | Three figures: years, guaranteed throughput in MWh, and minimum capacity retention at end of warranty. A year count alone does not survive two cycles a day. | Column — warranty years, with throughput noted in the remarks |
| 7 | BMS and EMS protocols | Physical interfaces (CAN, RS485, Ethernet, Modbus TCP) and the inverter models already validated by the supplier. | Gate — commissioning risk |
| 8 | Thermal and fire protection | Cooling method, cell-level monitoring, whether a suppression system is included or optional, and the enclosure rating it is tested to. | Gate — insurance and fire approval |
| 9 | Ingress rating and site envelope | IP rating for indoor or outdoor use, operating temperature range, and the service clearance the unit needs on all sides. | Gate — site fit |
| 10 | Compliance documentation | The actual test reports and their scope, not a logo block. The model and cell named in the report must match the unit being shipped. | Gate — see the market document table below |
| 11 | Scope of supply and Incoterm | Three explicit yes/no answers: is the PCS included, is BOS and installation included, are freight and duties included. Then the Incoterm, named. | Column — PCS included, BOS included, freight included (three columns) |
| 12 | Lead time and acceptance test | Weeks from purchase order to ex-works, plus the factory acceptance test items you will be allowed to witness. | Gate — schedule risk |
Why five fields become a price and seven do not
A price per kilowatt-hour is only meaningful when the kilowatt-hours and the scope behind them are the same. The worksheet therefore needs exactly seven inputs — price, nameplate kWh, DoD, PCS included, BOS included, freight included, warranty years — and derives two more: usable kWh and USD per usable kWh. Anything that cannot be expressed as one of those seven stays outside the arithmetic and is handled as a gate.
That split matters because the seven gate items are where the largest cost differences hide. A quote that omits the PCS is not 8% cheaper; it is a different product. A quote whose 6,000 cycles are measured at 60% DoD is not a longer-life product; it is a shorter warranty expressed in different units. Neither error shows up in a per-kWh comparison — both show up in the gate answers, which is why the gates must be cleared before the ranking is read.
Three reject rules worth applying before you rank anything
- No DoD, no entry. A supplier that gives usable capacity without the depth of discharge and the C-rate cannot be normalised, and should not be entered in the sheet on an assumed figure.
- No test report, no shortlist. Datasheet logos are marketing. The report number, issuing laboratory, standard edition and the model it covers are the evidence.
- No throughput, no lifetime comparison. If warranty is expressed only in years, the lifetime cost per usable kWh cannot be calculated and the cheapest quote may simply be the one with the shortest exposure.
Documents to add by destination market
Items 1–12 describe the product. The destination market decides which documents prove it. The same cabinet shipped to Rotterdam and to Jeddah carries a different file set, and a supplier who only sends a CE declaration of conformity has answered roughly half of the EU question.
| Market | What is added to the 12 items | Where the detail is |
|---|---|---|
| EU | CE declaration of conformity with the directives cited, IEC 62619 and IEC 62477-1 test reports, EN 50549-1 unit certificate, plus the national grid-operator documents. Battery Regulation (EU) 2023/1542 obligations are now phased in. | EU compliance document pack |
| UK | UKCA or accepted CE marking, BS EN IEC 62619, G98 notification or G99 approval depending on the aggregate at the connection point, G100 where export is limited, and fire-siting evidence. | UK compliance document pack |
| GCC | Country conformity certificate for customs (SASO SABER in Saudi Arabia, ESMA in the UAE), plus the local utility’s interconnection approval and an Arabic-labelled datasheet. | GCC guide — in preparation |
| LATAM | National conformity mark where one exists, the local electrical installation code, and the distribution utility’s distributed-generation connection process. | LATAM guide — in preparation |
Two documents travel everywhere and should be requested in the first email rather than at shipping: the UN38.3 test summary for transport, and the safety data sheet. Without them the unit cannot legally move, and a late request is a late shipment.
How to send the brief
Three inputs make a quotation accurate: 12 months of interval load data (or utility bills), a single-line diagram of the existing distribution, and the target application — peak shaving, backup, solar self-consumption or a combination. If interval data is not available, one week of logging on the main incomer is usually enough for a first-pass sizing.
Send the 12 fields as a table with a blank answer column, and ask each supplier to return it filled in alongside the quotation. Then enter the five priced fields into the quote comparison worksheet and read the gate answers first. Comparing two incomplete quotes on price alone is the most common cause of an undersized system.
Frequently asked questions
What is the minimum information a supplier needs for a quote?
A load profile, the target application and the site’s grid arrangement. Twelve months of interval data is ideal because it captures seasonal peaks; utility bills plus a single-line diagram are an acceptable fallback. Without the load profile, any capacity figure is a guess, and the resulting quote will be padded to cover the uncertainty rather than matched to the site.
Why do two 100 kWh quotes differ so much in price?
Because the nameplate capacity hides the variables that cost money: cell maker, usable depth of discharge, PCS power rating, thermal management, certification scope and what is included in the shipment. A quote with no switchgear, no commissioning and no test reports will always look cheaper. The 12 fields above make those omissions visible before the order is placed rather than after delivery.
Should warranty be measured in years or throughput?
Both, but throughput is the number that protects the buyer. A ten-year warranty that caps total energy throughput can expire early on a system doing two cycles a day. Ask for guaranteed MWh, the end-of-warranty capacity retention and the cycle count at a stated depth of discharge and temperature. Those three figures tell you whether the warranty matches the intended duty cycle.
Which certificates should be requested before shipment?
Request the underlying test reports, not just the logos: battery safety and transport documentation such as UN38.3, the CE marking scope and declaration of conformity, and the applicable IEC standards for the battery and the power conversion system. Check that the model and cell maker named in the reports match the unit being shipped, because certificates are often written for a different configuration in the same product family. The market-by-market additions are listed in the compliance document index.
Can this checklist be used for existing solar retrofits?
Yes, with two additions. State the existing inverter model and its export limit, and say whether the battery should be AC-coupled to the operating PV array or DC-coupled in a new build. Retrofits usually fail on communication compatibility between the BMS, EMS and the existing inverter, so ask the supplier to name previously validated inverter models in writing before confirming the order.
Want the checklist applied to your project?
Send your load profile and site conditions. We reply within 24 hours with a proposed configuration, the supplier answers to these 12 fields, and a quotation.
