Battery Energy Storage System Specification: From RFP to Priced Quote

If you have quoted a battery storage job, you know the price rarely goes wrong on the cells. It goes wrong in the sentences around them.

Those sentences say where the energy is counted, how long the warranty runs, who looks after the plant once the service contract ends, and which fire tests the fire authority will ask for.

This guide follows one battery energy storage system specification all the way from the request for proposals to a priced draft quote, line by line. The package is public, so you can check every page we cite.

It comes from the Las Gallinas Valley Sanitary District, which runs a wastewater plant in San Rafael, California. Its 154-page request for proposals asks for two batteries, a 207 kW unit and a 378 kW unit, each rated for 4 kWh per kW (page 7).

From that package we built an example draft quote, priced with sample rates. It has ten lines and comes to $1,315,600 plus TBD. The TBD is fire protection, because no fire standard is named anywhere in the 154 pages.

We use that draft all the way through. For each line we show what drives its price and where the package says it. Then we show where the package leaves money open, the questions to send the customer, and how to check the draft before it goes out.

This guide is for the proposal engineer or estimator at a battery storage integrator or installer, or at a maker of battery enclosures and inverters. If you want a general method for reading any package first, it is in reading bid packages.

What a battery storage quote contains

A battery storage quote is more than a price per kilowatt-hour. It is a list of priced lines, each tied to something the customer asked for, together with the terms that say what the price covers.

Every battery energy storage system specification asks for the same kinds of lines, even when the sizes and the wording change. Knowing them by heart is the fastest way to spot what a package leaves out.

Two units set most of the price

Two numbers describe any battery plant. Power, in kilowatts (kW), is how fast the plant can deliver energy. Energy, in kilowatt-hours (kWh), is how much it can store.

So "4 kWh per kW" means four hours of storage at full power. A 207 kW battery at 4 kWh per kW must store at least 828 kWh.

The battery itself is usually priced by energy, per kWh. The inverters, which turn the battery's direct current into the alternating current a building uses, are usually priced by power, per kW.

The lines of a complete quote

A complete battery storage quote usually carries the ten lines below. The example draft later in this guide has every one of them.

1. The battery energy, priced per kWh at the size the package asks for.
2. The inverters, also called the power conversion system, priced per kW.
3. Extra battery for fade, because lithium-ion cells slowly lose capacity as they age.
4. Switchgear and protection relays, which connect the battery to the building and disconnect it safely when something goes wrong.
5. Controls, monitoring and alarms, including the battery management system that watches every cell.
6. Installation, which covers labour, materials, concrete pads, trenching, conduit, wiring and stamped design drawings.
7. Commissioning and start-up, which means testing the plant on site until the customer accepts it.
8. A maintenance agreement for the years the package asks for.
9. Any warranty beyond what the battery and inverter makers give as standard.
10. Fire protection, and the test reports that prove the design is safe.

What sits around the lines

A quote that stops at the lines is not finished. Four more parts sit around them, and each one protects the price.

• The clarifications say, in plain words, which reading of the package you priced.
• The TBD lines show what you could not price yet, so nobody mistakes the total for a complete one.
• The calls show each decision the package leaves open, with the price of each reading.
• The questions for the customer ask for the facts that would close each open point.

A battery storage quote is only as safe as the readings written next to it. Two bidders can price the same plant at different totals and both be right, because they read the same page in two ways.

The worked example: a draft quote for two batteries

Here is the example draft quote for the Las Gallinas package. It is priced with sample rates, not with any real company's rates, so read the amounts as an illustration of how the lines behave.

The draft is dated 19 October 2026. Its title describes the job as two battery energy storage systems for the district, covering batteries, inverters, switchgear, warranty and maintenance.

The sample rates behind it

The example uses four sample figures. In a real quote, these come from your own rate book.

• Labour is priced at $118 an hour.
• Field service, such as a technician on site for commissioning, is priced at $1,350 a day.
• The margin is 22 percent.
• The rates are dated October 2026, so anyone reading the draft later knows how old they are.

The one call beside the battery line

The draft carries one call, which is a decision the package leaves open. Page 7 never says where the 4 kWh per kW is counted, so the draft prices the most likely reading and shows the other one beside it.

If the energy is counted at the meter instead of at the battery, the battery line rises from $748,800.00 to $819,200.00. The total then becomes $1,386,000.00 plus TBD. We come back to this call in detail below.

How to read the total

The total is $1,315,600.00 plus TBD, and the plus sign matters. The fire protection line could add a real amount once the fire authority says what it wants.

A draft that hid the TBD inside a round number would look finished and be wrong. A draft that shows the TBD tells the estimator and the customer exactly what is still open.

What drives the price of each line, and where the package says it

Each line in a battery storage quote has one or two things that move its price more than anything else. Here is each line of the example, with the page that sets it where the package gives one.

Battery energy: the size, the product and where it is counted

Page 7 sets both the sizes and the duration. It asks for "a minimum 207 kW BESS at Meter 6439" and "a minimum 378 kW BESS at Meter 4626", and then gives one rule for both.

So the 207 kW battery needs 828 kWh and the 378 kW battery needs 1,512 kWh. Together that is 2,340 kWh, which is the quantity on the first line.

The price of this line is simply the energy times your cost per kWh. At the sample $320.00 per kWh it comes to $748,800.00, which is more than half of the whole quote.

Three things move that cost per kWh:

• The product you choose matters most. Page 11 names "Tesla, SYL, Fortress, or equal", so you can offer one of those or an equal product.
• The word "minimum" means 2,340 kWh is a floor. Battery products often come in fixed cabinet sizes, so the energy you actually supply can land a little above it.
• The point where the energy is counted can add battery, as the call below shows.

The district's price form on page 27 has a column for "Make and Model". Your quote has to name the product, not just price it.

Inverters: one for each battery

The inverters are sized by power, so the quantity is 207 kW plus 378 kW, or 585 kW. At the sample $180.00 per kW the line comes to $105,300.00.

Page 11 sets what the inverters must do, and these requirements decide which models you can offer:

• Each inverter needs a minimum overload capacity of 120 percent, which means it must carry a fifth more than its rating for a short time.
• The output must be 480 volts AC nominal.
• Full load efficiency must be 98.3 percent or greater.
• The battery system must be "a grid-forming entity".

A grid-forming inverter can run the site on its own when the utility goes down, instead of only following the grid. That matters here, because page 7 asks for a seamless move to microgrid operation during an outage.

Grid-forming inverters usually cost more than the simpler kind. If your usual inverter cannot meet the 120 percent overload, you may also need the next size up, which raises this line.

Extra battery for fade

Lithium-ion batteries lose a little capacity every year as they age and cycle. That loss is called fade or degradation, and it is why the example carries extra battery from the first day.

The example adds 140 kWh, which is about 6 percent of 2,340 kWh, at the same $320.00 per kWh. The line comes to $44,800.00.

What drives this line is how hard the battery works and for how long. Page 12 asks the battery to "Discharge daily" during peak hours, which is about one cycle a day. Over a 20-year warranty, that is roughly 7,300 discharges.

Other buyers write their fade rules much more tightly. Los Angeles allows no loss of guaranteed energy until the last five years of a 15-year term, and AES Indiana asks for full nameplate power and duration for 20 years.

Las Gallinas gives no number at all. That is why this line needs a clarification, as we explain below.

Switchgear and the two relays on the price form

Page 27 is the district's price form. It asks for a separate price breakdown for each battery, and each breakdown has the same lines.

• The first two lines are the battery energy storage system and the inverters.
• Next come the switchgear and a line for the "SEL 735, 700G relay".
• Then come the 5-year maintenance agreement, a line called "Other", the balance of material and the labour.
• The last line is tax.

The SEL-735 is a meter that measures energy and power quality, and the SEL-700G is a protection relay used where a generator or a battery connects to the utility. Because the form names both, there is little room to swap them for something cheaper.

The example prices one set of switchgear with both relays for each site, 2 sets at $34,500.00, or $69,000.00. Your price comes from your supplier's quotation for the gear and relays, plus the wiring and the relay settings.

Page 7 adds more to this part of the job. It asks for the "Ancillary equipment, meters, transformers, grounding, and controls" that let each battery move from utility power to microgrid power without a break.

Controls, monitoring and alarms

Page 17 describes the battery management system and its data. It asks for "revenue" grade measurement, data stored at 15-minute intervals, and a live display that staff can view over the Internet.

That display has to stay available "for the entire term of the warrantee period". The package carries warranties of 10 and 20 years, so the online monitoring may have to run for up to 20 years.

The controls line needs to cover the data service for that long, or the quote needs to say how long it covers.

The example prices controls, monitoring and alarms at $12,600.00 for each of the two sites, or $25,200.00. Page 17 also lists the alarms that must notify staff, and one of them is written for a solar plant, which we cover below.

Installation, labour and materials

This is the second-biggest line in the example, one lot at $186,400.00. It covers the concrete pads, trenching, conduit, wiring and the stamped design drawings.

No single page sets this line. The scope spreads across the package, and it makes the contractor responsible for all the materials, labour, trenching, paving and grading needed for a complete system, with civil and structural drawings stamped by an engineer registered in California.

Pages 11 and 12 add material choices that raise the cost:

• All fasteners must be stainless steel grade 316 or better.
• All outdoor conduit must be rigid schedule 40, galvanized and unpainted.
• Exterior enclosures and boxes must be at least 14 gauge type 316 stainless steel, with seams welded all the way along and ground smooth.

The labour side is driven by hours times rate. This is a California public works job, so prevailing wages apply, and your labour rate has to reflect that. The example uses a sample rate of $118 an hour.

Commissioning and start-up

The example prices acceptance tests at both sites, 2 sites at $9,800.00, or $19,600.00. In a real quote, this line is mostly field service days times your day rate, which is $1,350 a day in the example.

The number of days depends on how many situations the plant must be tested in. Page 7 says each battery must work alongside other generators on the same property:

• At Meter 6439 there is a new 1 MW solar system, provided by others, and a backup generator.
• At Meter 4626 there is an existing 60 kW cogeneration system and a backup generator, and the battery must run in parallel with the cogeneration in microgrid mode.

Each of those generators adds a hand-over to test. More generators on site means more commissioning days, even though the batteries are small.

Maintenance agreement, five years

Page 7 asks for a "5-year maintenance agreement for each BESS". The example prices it at $27,000.00 per battery for the five years, or $54,000.00 for both.

That works out to $5,400 a year for each battery. What drives it is the number of site visits each year, travel to San Rafael, the parts you replace, and the remote monitoring you watch between visits.

The 20-year battery and inverter warranty

When the makers' standard warranties are shorter than 20 years, the difference has to be bought as an extended warranty or carried as your own risk. The example prices that extension as one lot at $62,500.00.

Page 10 also asks the contractor for its own warranty of at least 10 years, for no-cost repair and replacement of anything the makers do not cover. That is a separate promise, and your warranty line has to cover it too.

Twenty years is long for this kind of job. Among the other public battery storage documents in our sources, AES Indiana asks for three years, and SECI in India asks for five years with the battery covered to the end of its life.

Fire protection and test reports: TBD

We searched all 154 pages for a fire standard and found none. Page 10 asks for generating equipment certified by Underwriters Laboratories and for UL listed components, but it never names a battery system standard or a fire test.

Other buyers do name them. The Los Angeles specification, also written for California, lists "UL Standards 9540, 9540A", NFPA 855 and the "2025 California Fire Code" (page 5).

UL 9540A is a test that shows whether a fire in one cell spreads to the next cell, module and unit. A report for your exact product is either one you already hold or one you have to pay for.

A fire design can add suppression equipment, wider spacing between units, and test reports you may have to pay for. Since nobody can know which of these Las Gallinas will need, the example marks the line TBD instead of guessing.

Where the battery energy storage system specification leaves money open

Some pages can be read two ways, and each reading has a price. A good quote does not hide that choice. It carries the more likely reading, shows the other reading with its price, and writes both into the clarifications and the questions.

The example has one priced call. The other open points are handled with a carried line plus a clarification, or with a TBD and a question.

The call: where the 4 kWh per kW is counted

Page 7 asks for 4 kWh per kW and never says where that energy is counted. It does place each battery at a utility meter, but that tells you where the battery connects, not where its kilowatt-hours are measured.

The difference is real energy. Between the battery and the meter sit the inverter, the wiring and the cooling, and each one uses a little of the energy on the way out.

The example assumes those losses come to about 9 percent. That is a sample figure for the example, not a number from the package.

The example carries the first reading. Battery energy is usually rated at the battery itself, and page 7 says each battery "shall be rated for" its energy, which sounds like a nameplate figure.

The second reading is not far-fetched, though. When buyers do say where energy is counted, they often pick the far end.

• Los Angeles writes that "All parameters shall be measured at the POI" (page 13), meaning the point where the plant meets the grid.
• SECI in India shows its own losses in a table: 1200 MWh owed at its 220 kV substation means 1248.0 MWh at the inverter terminals in year 1 (Annexure B, page 4).
• Cyprus counts energy at its point of connection, from a full battery down to empty (pages 2 and 3).

So the quote shows the meter reading as a call with its price. If the estimator flips the call, the total moves by $70,400 at once, and the question to the customer asks which reading the district means.

Fade: what "warranted against degradation" means

Read word for word, page 10 could mean the battery may never lose any capacity in its life. No lithium-ion battery does that unless more battery is added over time.

The example reads it the practical way. It carries 140 kWh of extra battery on day one, $44,800.00, to cover fade under the makers' degradation curve at about one discharge a day.

If the district really means no loss at all for twenty years, the extra battery would be much larger, or it would be added in stages over the years. That price is not in the example total.

So the clarification has to say which fade basis the quote covers. If the district asks for the stricter reading, the estimator can price it as a separate option.

A 20-year warranty with five years of maintenance

Page 10 asks for a 20-year warranty on batteries and inverters, but page 7 asks for a maintenance agreement of only five years. Nobody in the package looks after the plant in years 6 to 20.

The price impact is easy to size from the example. Five years of maintenance for both batteries costs $54,000.00, so fifteen more years at the same yearly rate would be three times that, $162,000, before any yearly increase.

That money is not in the example total, and it should not be, because the package does not ask for it. But you are still giving a 20-year warranty on equipment that you will not be paid to maintain.

So the quote handles it in two places. The clarification says the warranty assumes maintenance to the makers' schedule in every year, and the question asks the district who maintains the batteries after year 5.

An efficiency figure written for solar panels

Round-trip efficiency is the energy you get back divided by the energy you put in. STC means standard test conditions, which is a solar panel term, so the page does not say where or how the district will measure it.

The figure is high next to other buyers. AES Indiana asks for at least 85 percent at its high-voltage connection, including the power the cooling and controls use, and SECI asks for 86 percent at the inverter terminals, also including that power.

No line in the example moves because of this sentence. The risk is in the promise, because a figure above 92 percent measured at the meter may be one your equipment cannot reach, and it sits under a 20-year warranty.

So the quote states where and how its efficiency figure is measured. If you cannot meet the figure as written, list it on the district's "Omissions and Exceptions" sheet on page 28.

An alarm written for a solar plant

Irradiance is the strength of sunlight. A battery's output follows its charge and discharge schedule, not the sun, so this alarm was almost certainly copied from a solar specification.

The example's controls line prices battery alarms instead: the inverter shutting down, and output falling outside its schedule.

If the district insists on an irradiance alarm, it would need a sunlight sensor or data from the solar system, which page 7 says another party provides. That cost is not in the example, so the clarification says how the alarms are set.

TBD lines and the questions for the customer

Some things in a package cannot be priced by anyone until the customer answers. A good draft says so openly instead of filling the gap with a guess.

Why the draft says TBD instead of guessing

A guess looks exactly like a price once it sits in a column of numbers. If the fire protection line were filled with a round figure, nobody reading the total later would know it was a guess.

A guess on fire protection could be too low, and you would carry the gap after award. It could also be too high, and you would lose a job you should have won. TBD keeps the line visible until the fire authority answers.

The three questions to send

The example turns each open point into a question, written so it can be pasted straight into the reply to the district.

When to send them

The package sets a deadline for written questions before proposals are due, and the district may answer by addenda sent to every bidder. Send the questions early, so the answers can still change your price.

If no answer arrives in time, the quote still goes out. The clarifications carry your readings, and the "Omissions and Exceptions" sheet on page 28 lists anything you left out or could not meet. We cover building that list in pre-bid risk assessment.

Clarifications to write into the quote

Here is how the example's readings could be worded in the quote itself. Each sentence matches a line, a call or a TBD in the draft.

• Battery energy of 4 kWh per kW is provided at the battery, 2,340 kWh in total, and energy counted at the utility meter can be provided for an added $70,400.00.
• Fire protection, fire testing and fire test reports are excluded until the fire authority's requirements are confirmed.
• Maintenance is included for five years for each battery, and the 20-year warranty assumes maintenance to the makers' schedule in every year.
• The extra battery covers fade under the makers' degradation curve at about one discharge a day.
• Round-trip efficiency is stated at the battery, at the makers' test conditions.
• Alarms are set against the battery's schedule rather than against solar irradiance.

A fixed price is only as safe as the assumptions written next to it. Why that matters after award is in fixed price contract risk.

How to check a draft before it goes out

A draft quote is a starting point for the estimator, not the finished quote. These checks catch the usual misses in a first draft, whoever wrote it.

Check the quantities against the page

Redo the arithmetic from page 7 by hand. 207 kW plus 378 kW is 585 kW, and 585 kW times 4 is 2,340 kWh.

If a quantity in the draft does not trace back to a page, find out where it came from before you send anything.

Re-sort the lines into the district's price form

The draft prices both sites together, but page 27 wants a separate breakdown for each battery. So the battery line splits into 828 kWh for the 207 kW site, $264,960.00, and 1,512 kWh for the 378 kW site, $483,840.00.

The inverters split the same way, into $37,260.00 for the 207 kW site and $68,040.00 for the 378 kW site. The other lines follow the table below.

Notice the last row. The form has a tax line for each battery, and the example draft has none, so the estimator adds tax the way the company normally does.

Check that every promise in the package has a line

Go through the pages that make promises and find the line that pays for each one.

• Page 7 asks for the utility interconnection paperwork and the paperwork for California's Self-Generation Incentive Program, which helps pay for on-site batteries. Each battery already has a conditional reservation, so make sure one of your lines covers that office work.
• Page 10 asks for both a 20-year warranty on batteries and inverters and a 10-year contractor warranty, so check that the warranty line covers both.
• Page 17 asks for online monitoring for the whole warranty term, so check how many years of data service the controls line covers.
• Page 7 asks for five years of maintenance for each battery, which means two agreements, not one.

Check the lines that have no single page

Three lines in the example have no single page: the inverters, the installation and the commissioning. Their sizes come from page 7, but their scope is spread across the package.

These are the lines where an estimator's own knowledge matters most. Walk the site layout, count the trench lengths and the commissioning days yourself, and change the draft wherever you know better.

Check the rates, the call and the total

• Check that the rates are current and dated. The example's rates are dated October 2026, and the labour rate has to meet California prevailing wages.
• Check that the call is set the way you want it. If the pre-proposal answers say the meter, flip it before the quote goes out.
• Check that the total is written with its TBD, as $1,315,600.00 plus TBD, and that the clarifications match the readings you carried.
• Check how long the price must hold. Public owners often ask for a set validity period, and our note on how long a quote should be valid for covers what that means for your rates.

A specification compliance matrix helps here, because it keeps every requirement tied to its page and to the line that prices it.

How Mavlon's AI Quoting Engine produces this kind of draft

The draft in this guide is the kind of output Mavlon's AI Quoting Engine is built to produce. A customer's bid package goes in, and a priced draft quote comes out in the manufacturer's own pricing, ready for the estimator to review and send.

It prices the way your company prices

The engine learns each company's pricing from its own past bid packages, the quotes it actually sent, and its costing workbooks and rate books. So the cost per kWh, the labour hours, the day rate for field service and the margin all come from your company's own rules.

The example here uses sample rates. With your own rate book and past quotes, the engine prices the way your team prices.

What the draft gives the estimator

• Every line has its quantity, unit price and amount, and keeps the page it came from.
• Lines the package does not settle say TBD instead of a guess, like fire protection in the example.
• Decisions the package leaves open become calls with the price of each reading, and flipping a call moves the total at once.
• Anything nobody can answer from the documents becomes a question for the customer, ready to paste into the reply.

The estimator still decides

The estimator checks the draft, changes what they know better, and sends the quote. The engine does not decide whether the offer complies with the package, and it does not set the final price.

For a battery storage team, the gain is time and consistency. The first draft arrives in minutes instead of days of reading, so the estimator can spend the day on the calls and the customer questions, and the company can quote more bids without adding estimators.

Because the draft follows the company's own rules, the pricing stays consistent even when a senior estimator is away. Fewer things get missed, because spares, field service, tests and TBDs all sit on the draft, each with its page.

How a pilot is judged

A pilot tests the engine blind on the customer's own past quotes, with the pass bar agreed in writing. The published bar is 7 of 10 job totals within 15 percent of the quote that was actually filed. The details are in the pilot protocol.

For the wider picture of what the engine does across products, see AI quoting software for manufacturing, and for the estimator's side of the work, AI for estimators.

Sources

The example draft quote is built from the first document below. The other documents are used only as evidence for how other buyers write the same requirements.

• Request for Proposals, Battery Energy Storage Systems, Job No. 24600-14, Las Gallinas Valley Sanitary District, April 5, 2024.
• Attachment A, Standalone Energy Storage System Specifications for LADWP Transmission Reliability Projects, Southern California Public Power Authority for the Los Angeles Department of Water and Power, April 2026.
• Attachment B, Energy Storage Specifications, Q3/Q4 2026 RFP, same owner, July 2026.
• Petersburg BESS Project, Exhibit F, BESS Scope of Work and Technical Requirements, Rev 0, AES Indiana, February 6, 2023.
• Solar Energy Corporation of India, RfP No. SECI/C&P/OP/15/0001/25-26, 600 MW / 1200 MWh BESS (DC Package), August 4, 2025: request for proposals, Annexure B, Amendment-01 (September 15, 2025), Amendment-02 (September 23, 2025), clarifications, service level agreement, and the result, which names Pace Digitek Limited at INR 11,59,31,14,407.03.
• Annex II, Appendix 2, Technical Specification: Installation, Performance and Safety Specifications of Battery Energy Storage Systems, Cyprus Ministry of Energy, Commerce and Industry, consultation draft, May 17, 2024.