BESS Sizer.
— Sizer · BESS peak-shave · MNRE / CEIG / IEC LFP
The battery your demand profile justifies.
Conservative model: 20% peak-shave, LFP 90% DoD per IEC 62619, 92% round-trip, 350 cycles/year. Solar self-consumption 35% of generation at PR 0.78 per MNRE solar standard. Technical sizing only — pricing follows a written estimate after review.
BESS size
660 kWh
LFP · 90% DoD · 90 kW shave
Inverter
100 kW
shave + evening solar discharge
Daily throughput
544 kWh
peak-shave + stored solar
Cell life
~ 12 yr
cycle- or calendar-limited
A planning link that reopens this exact configuration — not a quote.
- pack class
- industrial
- peak shaved
- 90 kW
- solar shifted
- 184 kWh / day
- co₂ avoided
- 43 t / yr (solar-shifted)
- peak-shave
- 20% of peak demand
- lfp standard
- IEC 62619 · IS 16270
- usable dod
- 90%
- round-trip
- 92%
- cycles / year
- 350
- calendar life
- 12 yr conservative cap
- pcs window
- 4 h evening solar-shift window
- solar standard
- MNRE PV · IEC 61724-1
- self-consumption
- 35% of daily generation
- sun hours
- 4.5 / day
- solar pr
- 0.78
- interconnection
- CEIG approval ≥ 100 kWh
+ Model assumptions (12)− Model assumptions
Indicative — LFP cell sizing per IEC 62619 / IS 16270, solar PR per MNRE / IEC 61724-1, grid interconnection per Central Electricity Authority (CEA) Technical Standards. Final design needs measured interval-meter demand data, a site grid-interconnection study, and CEIG approvals above 100 kWh. Pricing follows a written estimate after technical review.
What changes this estimate
- Measured interval-meter demand data — peaks vs average
- Evening grid tariff vs solar export / feed-in tariff
- Site grid-interconnection study
- CEIG approval pathway above 100 kWh
A planning link that reopens this exact configuration — not a quote.
Method
How this is calculated
Battery (kWh) = (peak-shave energy + stored-solar energy) ÷ 90% depth-of-discharge ÷ 92% round-trip efficiency, snapped up to 10 kWh steps.
Peak-shave energy = peak load × 20% shave fraction × peak hours. Stored-solar energy = array kWp × 4.5 sun-hours × 0.78 performance ratio × 35% self-consumption shift.
Years-to-replacement is min(cycle life, the 12-year calendar cap) — at typical daily cycling the calendar cap binds first. Neither figure affects the size.
Worked example — 450 kW peak · 4 h/day · 150 kWp solar
- Peak load:
- 450 kW, 4 h/day
- Solar:
- 150 kWp, shifted
- 1 · Peak-shave energy450 × 0.2 × 4 = 360 kWh
- 2 · Stored solar150 × 4.5 × 0.78 × 0.35 = 184.3 kWh
- 3 · Batterysum ÷ 0.9 ÷ 0.92 → 10 kWh steps = 660 kWh
Battery: 660 kWh LFP
Open the calculator and enter the inputs above to reproduce it. Every figure above was computed by the same engine the BESS Sizer runs — the example cannot drift from the tool.
Constants and assumptions
- Depth of discharge: 90%LFP planning figure
- Round-trip efficiency: 92%battery + PCS chain
- Performance ratio: 0.78Indian rooftop planning PR
BMS · BESS · LFP
Peak demand + solar + storage strategy in, indicative LFP battery size, inverter rating, daily throughput and cell life out. Vertiv, Delta, Fuji-class deployments.
- Chemistry
- LFP
- Round-trip
- 92%
- Usable DoD
- 90%
- Cell life
- 15–20 yrs
· Engineering advisory · BESS Sizer
What the kWh figure predicts about the deployment.
The recommended LFP battery size is the brief-stage budget. The deployment requires the cell-level monitoring discipline, the thermal-and-fire-NOC pathway and the operational continuity below.
Deployment observations
- BESS sizing against grid-tied peak-shaving is not the same architecture as BESS sizing against off-grid or hybrid-with-DG — the off-grid model requires hourly load profile and PV generation curves, not just peak demand. Sending the load curve is the design-phase deliverable, not the spec sheet.
- LFP cell-level monitoring with active balancing is the floor specification for any stationary BESS — without active balancing, cell drift over the first 18-24 months collapses the usable capacity to 60-70% of the nameplate.
- Round-trip efficiency degrades with depth-of-discharge — sizing against an 80% DoD floor preserves both round-trip efficiency and cycle life; sizing against 100% DoD compresses both.
Redundancy posture
- BESS rack failure is contained at the rack level if the system architecture has rack-level disconnect; a full-system trip on a single-rack event indicates an architectural under-spec, not a hardware failure.
- Inverter redundancy (N+1 hybrid inverter pool) is the typical critical-load architecture; the BESS holds capacity even if one inverter is out of service, with the load shedding gracefully across the remaining inverters.
Environmental considerations
- Battery-room thermal management is the leading silent failure mode in stationary BESS — LFP cells de-rate above 35°C and degrade rapidly above 45°C. Battery-room HVAC is sized against the full-discharge thermal envelope, not the standing-charge load.
- Fire-NOC pathway for stationary BESS varies by state and by capacity — Assam, Meghalaya and Bengal each have separate procedural pathways. CEIG approval and electrical-inspector sign-off are part of the turnkey scope, not a post-handover exercise.
- Monsoon-climate ingress into the battery enclosure is a documented failure mode — IP-rated enclosures and condensation-drain provisioning are part of the spec, not the catalogue default.
Commissioning discipline
- Cell-level capacity test at commissioning — every cell's actual capacity measured against nameplate, signed off as the baseline against which annual fade is measured. Without that baseline, the warranty argument is impossible to make.
- Load-profile verification against the actual DISCOM consumption pattern — the dispatch model is only as accurate as the demand input; the load curve shifts during the system's life and is part of the AMC review.
- Net-metering paperwork closed at handover — DISCOM agreement, meter swap and bidirectional measurement configuration witnessed and signed off. Net-metering paperwork stuck in DISCOM post-handover is the leading cause of a system not delivering its modelled throughput.
Lifecycle implications
- LFP cells carry a 5,000-7,000 cycle service envelope at 80% DoD — for typical daily peak-shaving (~330 cycles/year), the cell life is 15-20 years to 80% capacity. The inverter envelope is shorter (8-12 years) and is the leading refresh signal.
- BMS firmware refresh discipline matters — cell-balancing algorithms evolve, and the AMC schedule holds a firmware-update window each year with the per-cell calibration export-and-restore procedure rehearsed.
Expansion readiness
- Capacity expansion (additional rack) within the existing inverter envelope is a configuration-and-cabling exercise; beyond the inverter envelope, a parallel inverter and rack is the minimum incremental scope.
- Hybrid-with-DG migration is supported on most modern hybrid inverter classes — DG paralleling and BESS arbitrage across the DG runtime is a configuration extension, not a re-cabling exercise.
Verification status: Conditional engineering model — assumptions stated · Independently reference-tested · reviewed 2026-08-30
· Engineering notes
How to read this tool’s output
Stage 2 (survey) or stage 3 (design). Use after the load schedule is complete and the ride-through target is agreed with the client.
The assumptions, limits and reference architectures behind this
What an engineer should know
The assumptions behind the numbers this tool produces.
- Battery capacity is sized from the peak-shave energy plus stored-solar energy, divided by 90% depth-of-discharge and 92% round-trip efficiency; years-to-replacement is min(cycle life, the 12-year calendar cap) — at typical daily cycling the calendar cap binds first, and neither figure affects the size.
- This is a peak-shave and solar-shift sizer, not a ride-through sizer — backup-duration duty (how long the load must ride through an outage) is the UPS Runtime tool's domain.
- LFP chemistry only — NMC is not modelled because TechnoGuru does not specify NMC for indoor commercial banks (NFPA 855 compliance).
When this tool is the right one
The project moments and room types this is built for.
- Mission-critical IT room migrating from VRLA to LFP at refresh cycle.
- Hospital ward block adding ride-through capacity for clinical equipment.
- Industrial site adding peak-shave + demand-charge management to existing UPS.
What changes the answer in practice
Field conditions that move the result away from the planning figure.
- Indoor install requires NFPA 855-compliant LFP — the calculator assumes this.
- Floor-loading on retrofit installs may govern cabinet selection more than capacity.
Defensible starting architectures
Vendor-neutral reference points, not a recommendation to buy — the right answer is the one that survives your site survey.
- Vertiv EnergyCore / Delta Modulon DPH-S in parallel with the existing online UPS; staged hybrid migration where downtime is unacceptable.
Common mistakes
Failure patterns we see on real projects.
- Sizing to nameplate UPS load instead of the audited true load — leaves the bank over-specified.
- Skipping the cycle-life assumption review — site-specific cycling profile may shorten or lengthen the refresh cycle.
How this lands against adjacent systems
What else has to be agreed before this output is safe to build to.
- BESS inverter integration with the existing UPS layer requires a BMS bridge (Modbus or BACnet) for orchestrated peak-shave.
What this tool does not do
Deliberate limits — where the estimate stops and design begins.
- Does not model peak-shave dispatch in detail — for load-arbitrage modelling, pair with the Energy & Efficiency Estimator.
- Does not size DG → solar+BESS crossover — that is the DG → Solar+BESS Crossover tool.
Where this tool fits
The building types this output is calibrated for — and, where we have said so, the ones it is not.
Best suited for
Not the tool to reach for
The standards and technologies this touches
Reference pages for the protocols, standards and systems behind this tool’s output.
· Example use
A boutique hotel in Shillong runs a 380 kW peak demand, has 220 kWp of rooftop solar stored for evening self-consumption and a steep evening load. The sizer points at a 610 kWh LFP pack with a 100 kW inverter — large enough to shave the 6 to 9 PM peak and carry a slice of the night load. The cell-cycle envelope holds the pack for fifteen-plus years of daily duty.
How to use the BESS sizing
Step 1
Enter peak load and hours
Peak kW and the daily hours the peak runs.
Step 2
Add solar if present
Array kWp and whether solar shifting should be stored.
Step 3
Read the battery size
Peak-shave plus stored-solar energy, through depth-of-discharge and round-trip efficiency, snapped to 10 kWh steps.
Step 4
Check replacement horizon
The cycle assumption drives years-to-replacement, not the size.
Step 5
Validate ride-through separately
Backup duration is the UPS Runtime tool's domain — this sizer does peak-shave and solar shift.
· Frequently asked
BESS sizing —
what people ask first.
Why LFP and not NMC?
Lithium iron phosphate is thermally stable, safer in occupied buildings and tolerates the daily deep-cycle pattern that peak-shaving and self-consumption demand. NMC has higher density but a worse safety and longevity profile for stationary use.
How conservative are the throughput numbers?
We use a flat round-trip efficiency of 92 percent, a 90 percent usable depth-of-discharge on the LFP pack, and the load profile you supply rather than escalated forecasts. The battery is grossed up for both loss factors, so the output is the floor, not the headline.
What about diesel-replacement applications?
Possible, but the model here is grid-tied. For diesel-replacement or off-grid hybrids we run a separate study with hourly load profiles and PV generation curves — send the data and we will quote a feasibility study.
Do you handle the regulatory side?
Yes. CEIG approval, fire-NOC for the battery room, electrical-inspector sign-off and DISCOM net-metering paperwork are all part of a turnkey BESS scope. We have closed projects across Assam, Meghalaya and West Bengal.
Which inverter and BMS brands do you specify?
Vertiv, Delta and Fuji-class hybrid inverters with manufacturer-grade battery management. Cell-level monitoring, active balancing and Modbus integration into the BMS are non-negotiable on our scopes.
Engineering toolkit
Next in this sequence
Calculators whose inputs or outputs connect to this one.
- Power · BESS · Solar
DG → Solar+BESS Crossover
DG capacity and monthly run-hours in — the kWp solar + kWh LFP BESS that displaces the genset's run-hours out, plus annual diesel litres displaced and CO₂ avoided.
kWp · kWh · yearsOpen - Power · UPS · Runtime
UPS Runtime Estimator
Critical load in kW + redundancy target in — runtime per battery string at 100/75/50% load, recommended VA rating and the load-vs-runtime curve. Online double-conversion UPS only.
kW · minutes · VAOpen - BMS · Energy
Energy & Efficiency Estimator
Adjust building variables and see indicative energy and CO₂ savings (kWh) for a BMS-driven energy upgrade plus daylight-harvesting LED retrofit. Conservative; defensible in a first conversation.
kWh · CO₂ savedOpen
· Begin
Sizing a battery
for a real building?
Send the load profile and the solar generation file. We will return a sized system and a dispatch model within two working days; pricing follows a written estimate after review.