Battery energy storage

Battery storage that earns its place

A battery energy storage system (BESS) stores electricity when it's cheap or plentiful and delivers it when it's expensive, scarce or missing. As pioneers in battery storage, we design, integrate, install and maintain BESS for commercial and industrial sites, solar plants and grid-connected projects, from single cabinets to multi-MWh containers.

Talk to usDoes storage pay here?What's inside a BESS
Fig.: Container and cabinet formats. Schematic, not to scale.

One battery, several jobs

Most batteries pay back by doing several jobs

In Tamil Nadu, a battery that does only one thing rarely justifies itself. We design for the combination your site needs, and the energy management system (EMS) decides minute by minute which job comes first.

Fig.: Several jobs, one battery. Schematic, not to scale.

  • Peak shaving & contract demand

    Cap the 15-minute maximum demand your distribution company (DISCOM) bills you on. HT billing uses the higher of recorded demand or 90% of contract demand, so the saving lands only if contract demand is formally reduced or recorded demand already sits above that floor.

    Best when: Peaky loads: induction furnaces, compressors, crushers, chillers, fast chargers.

  • Time-of-day shifting

    Charge in cheaper hours and discharge in the peak windows of the time-of-day (ToD) tariff. On its own the price spread is thin; stacked with other jobs it adds up.

    Best when: Large consumption in the 6–10 am and 6–10 pm peaks.

  • Solar shifting

    Store midday solar instead of exporting, banking or curtailing it, and use it after sunset.

    Best when: Rooftop or captive solar with a daytime surplus.

  • DG hybrid operation

    The battery takes short outages and light loads, so the diesel generator (DG) set starts less often and runs at efficient loading when it does.

    Best when: Frequent short outages; oversized or lightly loaded gensets.

  • Backup & ride-through

    Keep critical loads running through outages and voltage dips, when the system is designed and approved for islanded operation.

    Best when: Hospitals, cold rooms, continuous processes, server rooms.

  • Power quality & power factor

    When the power conversion system (PCS) is sized with spare kVA, it can supply reactive power and smooth fast load swings, helping you stay above power-factor penalty thresholds.

    Best when: Sites near the 0.90 power-factor threshold, or with sensitive processes.

  • EV charger buffering

    Let fast chargers draw short bursts from the battery instead of the grid connection, within limits the EMS enforces.

    Best when: Adding DC fast charging on a limited connection.

We don't publish savings percentages. The value depends on your tariff, load shape and outage history, so we calculate it from your data and show every assumption.

Tamil Nadu, hour by hour

Charge in the quiet hours, work in the peaks

Tamil Nadu's high-tension (HT) tariff adds 25% to energy used between 6 and 10 am and between 6 and 10 pm, and takes 5% off energy used between 10 pm and 5 am. Maximum demand is measured in 15-minute blocks. A battery can charge overnight or from midday solar, and discharge into both peaks.

Fig.: One day of battery duty on a Tamil Nadu HT tariff. Schematic, not to scale.

The HT tariff day, band by band

  1. 00:00–05:00Night rebate (−5%) · battery charges
  2. 05:00–06:00Normal · battery holds
  3. 06:00–10:00Morning peak (+25%) · battery discharges
  4. 10:00–16:00Normal · solar hours · battery charges from solar
  5. 16:00–18:00Normal · battery holds
  6. 18:00–22:00Evening peak (+25%) · battery discharges
  7. 22:00–24:00Night rebate (−5%) · battery charges
As of . A revised tariff order was pending.

The order sets the 25% peak charge and the 5% night rebate for the tariff period FY2022-23 to FY2026-27, which ends on 31 March 2027. The next order may change the windows or the rates. (TNERC T.O. 6/2025, cl. 3.1.1.9–3.1.1.10.)

Source: TNERC, Tariff Order No. 6 of 2025 (opens in a new tab) (30 June 2025, effective 1 July 2025).

Read: Tamil Nadu's peak-hour tariff, explained

Inside a BESS

Cells store it. Everything else keeps it safe.

A BESS is more than batteries. Cells store the energy; the battery management system (BMS) keeps every cell within safe limits; the PCS converts DC to AC and back; the EMS decides when to charge and discharge; and cooling, detection and suppression keep the whole system safe.

Fig.: From cell to container. Schematic, not to scale.

  1. Cell

    What it is

    Lithium iron phosphate (LFP) prismatic cells of about 3.2 V nominal each, where the energy is stored.

    What we check

    Cell test reports (IEC 62619 / UL 1973), traceability data.

  2. Module

    What it is

    Cells in series with busbars, sensors and a module-level BMS.

    What we check

    Receiving inspection, torque, insulation.

  3. Rack

    What it is

    Modules in series with a rack BMS, fuse and contactor.

    What we check

    String protection coordinated so one rack cannot feed a fault in another.

  4. Battery management system (BMS)

    What it is

    Monitors voltage, current, temperature, state of charge and health at module, rack and container level; balances cells; trips on limits.

    What we check

    Alarm thresholds, trip tests, data access.

  5. Container or cabinet

    What it is

    Racks plus cooling, gas and smoke detection, suppression, explosion venting and an emergency stop.

    What we check

    Layout, spacing, foundations, drainage, earthing, coastal corrosion protection.

  6. Power conversion system (PCS)

    What it is

    The bidirectional inverter between the battery's DC and your AC network.

    What we check

    Sizing, protection, anti-islanding and grid settings.

  7. Transformer & switchgear

    What it is

    Connect the PCS to your LT or HT network with protection relays.

    What we check

    Protection study, Electrical Inspectorate drawings and tests.

  8. Energy management system (EMS)

    What it is

    The controller that decides when to charge and discharge, and talks to meters, solar, DG sets and chargers.

    What we check

    Control logic for your use cases; communications; cybersecurity.

Formats & chemistry

Cabinet or container, AC or DC

Outdoor cabinets

All-in-one units with battery, PCS, BMS, cooling and fire protection in one enclosure, typically in the low hundreds of kWh each and paralleled for more. Suits factories, hospitals, campuses and commercial sites.

Containers

20-foot and larger containers holding several MWh, with separate PCS and transformer skids. Suits large industrial sites, solar plants and grid-connected projects.

Fig.: AC coupling. Schematic, not to scale.

AC-coupled

The battery has its own inverter and connects on your AC network. It's the usual way to add storage to an existing solar plant, and it keeps battery and solar choices independent.

Fig.: DC coupling. Schematic, not to scale.

DC-coupled

Battery and solar share an inverter on the DC side. It suits new hybrid plants, can capture solar energy that would otherwise be clipped, and shares components, though the shared inverter can limit battery output at high solar.

Source: NREL (now NLR), Evaluating the Technical and Economic Performance of PV Plus Storage Power Plants (opens in a new tab) (August 2017).

Why LFP

Lithium iron phosphate is the default chemistry for stationary storage: long cycle life, good thermal stability, and no cobalt or nickel. It made up over 90% of stationary battery storage installed worldwide in 2025. Sodium-ion is promising, especially in very cold climates, but was under 1% of lithium-ion production in 2025, so we evaluate it case by case.

Safety

Safety is designed in layers

No battery is zero-risk. Good design makes faults unlikely, catches them early and stops them spreading. India now has binding rules for this: the CEA's 2026 safety amendment adds a battery storage chapter that applies from 1 April 2027.

Fig.: Layers of protection, cell to site. Schematic, not to scale.

  1. Prevention

    Qualified LFP cells; a BMS monitoring voltage and temperature at cell, module and rack level; a two-fault-tolerant design that stays safe, or shuts down safely, after two independent faults.

  2. Detection

    Smoke, gas, heat and flame detection, plus door and ventilation alarms, all monitored.

  3. Suppression

    An automatic fire-suppression system in every battery container.

  4. Explosion control

    Forced ventilation with automated louvres, and automatic shutdown if ventilation fails.

  5. Separation & security

    Spacing between enclosures and from buildings; fencing at least 1.8 m high; CCTV and intrusion alarms.

  6. Response

    Manual and automatic emergency stops and an independent third-party fire-safety audit presented to the Electrical Inspector (both CEA requirements), plus a site emergency response plan that we share with the local fire service (good practice, NFPA 855).

The detailed chapter applies to BESS connected above 650 V. Systems at 650 V and below must meet 'relevant standards'. We design smaller systems to the same layered approach.

Source: CEA, CEA (Measures relating to Safety and Electric Supply) Amendment Regulations 2026 (opens in a new tab) (Gazette, 30 March 2026).

Read: what the CEA's 2026 BESS rules require

Standards

Certified equipment, tested on site

Certifications belong to the equipment. We specify equipment certified to these standards, check the test reports, and commission to the test methods. CHE Energy does not claim product certification.

Standards we specify and test to, by level.
LevelStandardsWhat it covers
Cell & batteryIEC 62619 (+ IEC 63056) or UL 1973Safety of industrial lithium cells and batteries.
TransportUN 38.3 / IS 18237 / IEC 62281Safe shipping of cells and batteries.
SystemUL 9540 or IEC TS 62933-5-1 + IEC 62933-5-2Safety of the complete energy storage system.
Fire test dataUL 9540AA test method, not a certification: how thermal runaway propagates from cell to unit. We use it to set spacing and fire design.
Performance testsIEC 62933-2-1 (IS 17067 Part 2/Sec 1)Available energy, round-trip efficiency and basic functions, at commissioning and every year.
Power conversionIEC 62477-1 / -2Safety of the power electronics.
Installation practiceNFPA 855 (2026 edition)Installation of stationary storage, including EV charging with integrated storage.
IndiaCEA Safety & Construction amendments 2026Binding BESS requirements from 1 April 2027.

Performance

Numbers that mean what they say

  • Round-trip efficiency, AC to AC

    We quote efficiency at the meter, including cooling and auxiliaries, the way the CEA's 2026 construction standards define it (minimum 70%). Cell-level figures in brochures aren't comparable.

  • Degradation & augmentation

    Batteries lose capacity with cycles and time. The CEA's 2026 standards set a minimum performance guarantee of 90%, 80% and 70% of output at 5, 10 and 15 years. Where a contract needs capacity held, we plan augmentation.

  • Usable energy

    Depth of discharge sets how much of the nameplate you can use; the CEA's minimum is 80%. We size for the energy you need to deliver, not the number on the label.

  • Warranties, back-to-back

    Product and performance warranties come from the maker. We make sure the terms, exclusions and test methods are clear before you sign, and that our commitments line up with theirs.

Fig.: Capacity steps down with age; augmentation lifts it back. Schematic, not to scale.

Source: CEA, Technical Standards for Construction of Electrical Plants and Electric Lines (Amendment) Regulations, 2026 (opens in a new tab) (Gazette, 23 June 2026).

Scale

From one cabinet to the substation

Behind the meter

Factories, hospitals, campuses and commercial buildings: design, EPC, integration and operations and maintenance (O&M) for storage on your side of the meter.

Solar + storage

New hybrid plants and retrofits to existing rooftop, captive and ground-mount plants. Energy passed through storage between a captive plant and its captive user now counts as captive consumption.

Developers & utilities

Owner's engineer services, specifications and factory acceptance test (FAT) witnessing, balance-of-plant works, commissioning support and long-term O&M for grid-connected storage in southern Tamil Nadu.

Illustrative. Schematic, not to scale.

India's National Electricity Plan projects 47.24 GW / 236.22 GWh of battery storage by 2031-32.

Source: Ministry of Power (PIB), Central Electricity Authority notifies the National Electricity Plan for the period of 2022-32 (opens in a new tab) (31 May 2023).

Ways to pay

Paying for storage, four ways

Since September 2025, consumers may develop, own, lease or operate energy storage. You can buy the system outright, pay for it as a service, or share the measured savings.

Source: Ministry of Power (PIB), Modernisation of the Power Sector and Reliable Electricity Supply (opens in a new tab) (3 August 2026 (rules notified September 2025)).

  • Capex EPC

    You own the system from day one. We design, supply, build and commission it, with an optional annual maintenance contract (AMC).

    You pay: Milestone payments

  • Storage-as-a-service

    CHE Energy or a financing partner owns the system; you pay a fixed monthly fee covering hardware, EMS and O&M under a service-level agreement.

    You pay: A fixed monthly fee over a multi-year term

  • BOO / BOOT

    We, with a financing partner, build, own and operate the battery, and you pay a capacity or per-kWh fee. Under BOOT, ownership transfers to you at the end of the term; under BOO, it does not.

    You pay: A capacity or per-kWh fee

  • Shared savings

    Our fee is a share of measured savings (demand charges, peak-hour energy or genset fuel) against a baseline agreed up front and verified from meter and EMS data.

    You pay: A share of verified savings

Compare engagement models

Existing systems

Ready for 1 April 2027?

If your battery is connected above 650 V, the CEA's safety chapter applies to it from 1 April 2027, including an independent third-party fire-safety audit under a CEA procedure, within a three-month window from that date. Systems at 650 V and below must meet the relevant standards the CEA is to list. Either way, it's a good moment for a health check.

Fig.: The CEA's BESS safety chapter applies from 1 April 2027. Schematic, not to scale.

  • Readiness review

    We check your system, drawings and records against the chapter and list the gaps.

    See our consulting services

  • Audit preparation

    We assemble the documents, test records and site information the auditor and the Electrical Inspector will ask for. We don't act as the auditor.

  • Take over the upkeep

    A baseline inspection and capacity test, then an AMC.

    How O&M takeovers work
Book a readiness review

Source: CEA, CEA (Measures relating to Safety and Electric Supply) Amendment Regulations 2026 (opens in a new tab) (Gazette, 30 March 2026). Regulations 122(M) and 122(N).

Buyer's checklist

Twelve questions for any supplier

Fig.: Twelve questions, ticked one by one. Schematic, not to scale.
  1. Which certificates cover the cell, the battery pack and the whole system, and who issued them?
  2. Can we see the UL 9540A test report, and at which level (cell, module, unit)?
  3. How is round-trip efficiency defined: AC to AC, including auxiliaries?
  4. What degradation curve does the warranty commit to, year by year?
  5. Who pays for augmentation, and does augmentation downtime count against availability?
  6. How is availability defined and measured?
  7. What does the warranty exclude: temperature, cycles per day, depth of discharge?
  8. How are detection, suppression and explosion venting designed, and to which standard?
  9. Who owns the EMS and the data, and can we get raw BMS data?
  10. Who services it locally, how fast, and with which spares on hand?
  11. What happens at end of life, and who takes the batteries back?
  12. Does the design meet the CEA 2026 BESS regulations that apply from 1 April 2027?

Want us to check a quote against these?

Talk to an engineer
Read the full checklist with explanations

Questions about battery storage

A BESS is a stationary battery system with its own power conversion, management software and safety systems, built to cycle daily and work with the grid, solar and generators. A UPS or inverter battery is sized to back up specific loads for a short time and mostly sits idle. Some sites use both.

It can, when it does several jobs: trimming maximum demand, moving energy out of the 6–10 am and 6–10 pm peak windows, storing surplus solar and cutting DG running. Price arbitrage alone is thin. We calculate the value from your bills and 15-minute data and show the assumptions; we don't promise a percentage.

For short outages, often yes, provided the system is designed and approved to island, with proper changeover. For long outages a hybrid usually makes more sense: the battery handles short interruptions and light loads, and the DG set handles long ones and runs less often.

Usually, with an AC-coupled battery that has its own inverter. We check your solar inverter and its warranty terms, your metering arrangement (net, gross or open access), protection and space first.

Only if it's designed and approved for islanded operation, with proper transfer switching. A grid-tied system without that design shuts down with the grid, as anti-islanding rules require.

It depends on how hard it's cycled and how hot it runs. Industry planning references such as NREL's use about 15 years for lithium-ion storage with augmentation, and the CEA's 2026 standards set minimum output guarantees of 90%, 80% and 70% at years 5, 10 and 15.

With layered design, yes: qualified LFP cells, cell-level monitoring, detection, suppression, explosion venting, separation distances and emergency stops, following the CEA 2026 BESS safety chapter and the OEM's fire-test data.

Typically DISCOM (TNPDCL) approval for the connection or load change, and Electrical Inspectorate drawing approval, then the safety certificate, which is issued by the Electrical Inspector up to 630 kVA, the Senior Electrical Inspector from 630 to 2,500 kVA and the Chief Electrical Inspector to Government above 2,500 kVA, applied for through the Single Window portal. From 1 April 2027, BESS above 650 V also need an independent fire-safety audit. We prepare and track all of these.

Cabinets need a level plinth with clearance for maintenance and fire separation; containers need crane access. Near the coast we specify higher corrosion protection and sealed enclosures, and design drainage for monsoon rain.

The central viability gap funding (VGF) schemes support utility-scale projects procured by states and utilities, not commercial or industrial sites. For businesses, the levers are the tariff savings themselves, financing models and tax treatment (ask your CA). GST on lithium-ion batteries (HSN 8507) is 18%.

Storage batteries are 'industrial batteries' under India's Battery Waste Management Rules 2022. They must be collected and recycled or refurbished, not landfilled. We write an end-of-life plan into the contract and work with registered recyclers.

Since September 2025, consumers may develop, own, lease or operate energy storage. See our engagement models for capex, storage-as-a-service, BOO/BOOT and shared-savings options.

Sources for these answers

Start with a conversation

Tell us the jobs the battery must do.

A phone call is enough to start. If you have them, 12 months of electricity bills, 15-minute meter data, DG running hours and any EV plans let us come back with a first view of what fits.

Talk to an engineerTalk to an engineer

Call +91 7200788891WhatsApp (opens in a new tab)info@che-energy.in