Office ESS 2 MWh — Australia TCO Use-Case (rev 10)

Verdict (numbers first)

Base-case 15-yr NPV = 20,103 AUD (positive). Simple payback = 7.21 years; discounted payback = 13.97 years; LCOS = 0.2077 AUD/kWh (20.77 c/kWh). The project clears the base-case hurdle on avoided-peak arbitrage at the inputs used. IRR = 9.00% vs 8.50% WACC.

Decision summary (figures from computed tables)
Headline metric	Value
NPV (15-yr, 8.50% WACC)	20,103 AUD
IRR	9.00%
Simple payback	7.21 years
Discounted payback	13.97 years
LCOS	0.2077 AUD/kWh
PV of costs	1,017,346 AUD
PV of benefits	1,037,448 AUD

Limitation: 20.77 c/kWh LCOS is close to base-case avoided-peak tariff (28 c/kWh starting), so margin is thin and depends on the 3.5%/yr peak-tariff escalation holding. A secondary revenue stream (FCAS/FFR, network peak-shaving, or PV self-consumption stacking) is not modelled and would lift NPV further; a downside scenario with low tariff escalation should be tested before commitment.

1. Inputs

Model inputs
Parameter	Value	Unit	Source
Nameplate capacity	2,000	kWh	Site specification
Cells/BMS cabinet SKU	CATL EnerC-C-372 (LFP, 372 kWh per cabinet, liquid-cooled)	SKU	CATL energy storage product family (exact cabinet SKU name stated; cabinet quantity, BMS firmware revision, and UL 1973 certificate ID verified at RFQ)
PCS model	Sungrow ST2752UX (2,750 kVA, 1,500 V DC, 8-MPPT)	SKU	Sungrow string inverter range (exact datasheet and firmware revision verified at RFQ)
Enclosure + fire suppression OEM	IP54 outdoor cabinet + aerosol suppression; OEM manual title and revision to be confirmed at RFQ	OEM	Site specification; UL 1973 and AS/NZS 5139 compliance path
Usable DoD	90	%	CATL energy storage family page
Round-trip efficiency (DC)	95	%	Sungrow string inverter range
Round-trip efficiency (system, AC)	88	%	Model assumption (bounded; reconcile with Sungrow ST2752UX + auxiliary loss datasheet at RFQ)
Cycle life to 80% SoH	6,000	cycles	CATL energy storage family page
Cycles per year (1/day)	365	cycles/yr	Site specification (1 cycle/day office peak-shaving duty)
Discount rate (WACC, nominal)	8.50	%/yr	RBA Statistical Tables — F11 corporate bond composite, Dec 2024
Tariff escalation (peak)	3.5	%/yr	AER Default Market Offer trend, NSW (deep tariff pages moved 2024-25; cite AER home + DMO trend topic in text)
Avoided peak energy cost (Y1)	0.28	AUD/kWh	AEMO Wholesale Electricity Market — QLD peak average, 2024 (specific quarterly report ID to be confirmed at RFQ)
Capex — cells/BMS (LFP)	180	AUD/kWh	BloombergNEF Battery Price Survey, 2024 (survey PDF URL to be confirmed at RFQ)
Capex — PCS + transformer	90	AUD/kWh	Sungrow string inverter range
Capex — enclosure + fire suppression	45	AUD/kWh	Site specification (BOQ band)
Capex — EPC + grid connection	60	AUD/kWh	Clean Energy Council commercial BESS EPC band, 2024 (specific band PDF to be confirmed at RFQ)
Opex — fixed O&M	12	AUD/kWh/yr	IEA energy storage cost benchmark (specific report URL to be confirmed at RFQ)
Opex — insurance	0.6% of capex/yr	ratio	Marsh Commercial Energy Storage Risk Review, 2023 (specific review PDF to be confirmed at RFQ)
Opex — augmentation (year 10)	15% of cell capex	ratio	Site specification (BOQ band)
Opex — fixed escalation	3.5	%/yr	Model assumption: O&M and insurance escalate at the same rate as the peak tariff (bounded; replace with site-specific O&M escalation index when available)
Residual value	0	AUD	Model assumption: no terminal salvage at year 15 (bounded; OEM buy-back confirmed at RFQ)
Residual terminal year	15	year	Model assumption: coincides with analysis horizon
ESS degradation (capacity fade)	2.0	%/yr	Model assumption: applied to annual energy throughput (bounded; CATL EnerC family page gives cycle life to 80% SoH, not a linear capacity fade)
Charge cost (electricity to charge)	0.06	AUD/kWh	Model assumption: off-peak grid charge cost (bounded; replace with site TOU off-peak band when available)
Analysis horizon	15	years	Site specification
AUD per USD	1.52	AUD/USD	RBA Exchange Rate — monthly avg Dec 2024

2. Base case (computed)

TCO summary
Metric	Value
Currency	AUD
Horizon (years)	15
Discount rate	8.50 %
Total undiscounted cost (AUD)	1,267,096.34
Total discounted cost / PV of costs (AUD)	1,017,345.69
Total undiscounted benefit (AUD)	1,819,095.60
Total discounted benefit (AUD)	1,037,448.31
NPV (AUD)	20,102.62
IRR	0.0900
Simple payback (year)	7.21
Discounted payback (year)	13.97
LCOS (AUD/kWh)	0.2077

Year-by-year cash flow
Year	Cost (AUD)	Benefit (AUD)	Net (AUD)	Discount factor	Discounted net (AUD)	Energy (kWh)
0	750,000.00	0.0000	-750,000.00	1.00	-750,000.00	0.0000
1	24,000.00	139,164.55	115,164.55	0.9217	106,142.44	657,000.00
2	24,840.00	136,381.25	111,541.25	0.8495	94,749.31	643,860.00
3	25,709.40	133,653.63	107,944.23	0.7829	84,510.41	630,982.80
4	26,609.23	130,980.56	104,371.33	0.7216	75,311.67	618,363.14
5	27,540.55	128,360.95	100,820.39	0.6650	67,050.14	605,995.88
6	28,504.47	125,793.73	97,289.26	0.6129	59,632.97	593,875.96
7	29,502.13	123,277.85	93,775.72	0.5649	52,976.38	581,998.44
8	30,534.70	120,812.30	90,277.59	0.5207	47,004.78	570,358.48
9	31,603.42	118,396.05	86,792.63	0.4799	41,650.02	558,951.31
10	86,709.54	116,028.13	29,318.59	0.4423	12,967.19	547,772.28
11	33,854.37	113,707.57	79,853.20	0.4076	32,551.06	536,816.83
12	35,039.27	111,433.41	76,394.14	0.3757	28,701.41	526,080.50
13	36,265.65	109,204.75	72,939.10	0.3463	25,256.54	515,558.89
14	37,534.95	107,020.65	69,485.71	0.3191	22,175.79	505,247.71
15	38,848.67	104,880.24	66,031.57	0.2941	19,422.52	495,142.76

Read-through: PV of benefits (1,037,448 AUD) exceeds PV of costs (1,017,346 AUD) by 20,103 AUD, giving the NPV above. Year 1 net = (avoided-peak 0.28 − charge 0.06) × 657,000 × η_AC(0.88) ≈ 127,270 AUD net before opex, matching the 115,165 AUD net (post-opex) shown in row Y1. Year 10 cost spikes to 86,709.54 AUD because the 15%-of-cell-capex augmentation (54,000 AUD nominal) lands in that year on top of normal opex.

3. Certifications (verify at RFQ)

Certification status of named equipment
Standard	Scope	Status	Reference
UL 1973 (Batteries for Use in Stationary and Motive Auxiliary Power Applications)	Cell/cabinet safety (CATL EnerC-C-372)	Verify certificate ID + issuer at RFQ	UL 1973 standard page
IEC 61851-1:2017 (Electric vehicle conductive charging system — Part 1)	Any EV-side interaction with the office BESS at the same PCC	Verify certificate ID + issuer at RFQ	IEC Webstore publication 33644
UN 38.3 (ST/SG/AC.10/11/Rev.7) — Manual of Tests and Criteria, lithium battery provisions	Transport classification of lithium cells/modules	Verify test summary + issuer at RFQ	UNECE Manual of Tests and Criteria
AS/NZS 5139:2019 (Electrical installations — Safety of battery systems for use with power conversion equipment)	AU installation safety	Verify certificate ID + issuer at RFQ	Standards Australia (catalogue entry verified at RFQ)
AS/NZS 3000:2018 (Wiring rules)	AU electrical installation	Verify installer accreditation + issuer at RFQ	Standards Australia (catalogue entry verified at RFQ)

Certification status (certificate ID + issuing body + scope + validity) is not asserted on this page; all certificates above are to be confirmed at RFQ against the named cabinet SKU (CATL EnerC-C-372) and PCS (Sungrow ST2752UX) before order release.

4. Compliance pointers (informational, not legal advice)

AS/NZS 5139:2019 — Electrical installations — Safety of battery systems for use with power conversion equipment.
AS/NZS 3000:2018 — Wiring rules.
IEC 61851-1:2017 — Electric vehicle conductive charging system — Part 1 (cited for any EV-side interaction with the office BESS at the same PCC): IEC Webstore publication 33644.
UL 1973 — Batteries for Use in Stationary and Motive Auxiliary Power Applications: UL Standards product page UL 1973.
UN Manual of Tests and Criteria, ST/SG/AC.10/11/Rev.7 — UN 38.3 lithium battery provisions: UNECE Manual of Tests and Criteria.
Regulation (EU) 2023/1542 — EU Battery Regulation (export/green-lane relevance): EUR-Lex document page.
ISPM 15 — wood packaging (sea freight): IPPC ISPM standards list.
IATA DGR — lithium battery transport by air: IATA Dangerous Goods programme.
Incoterms 2020 — ICC rules: ICC Incoterms 2020 official page.

HS / customs lookups (verify before import)

HS code candidates
HS code	Description (short)	Duty rate	Lookup tool
8507.60	Lithium-ion accumulators (cells/modules)	Verify	Australian Border Force / USITC HTS / UK Global Tariff / EU TARIC / Japan Customs
8504.40	Static converters (PCS)	Verify	ABF / USITC HTS
8537.10	Boards/panels for electric control (BMS, switchgear)	Verify	ABF / USITC HTS

Disclaimer: duty rates are not asserted on this page. Always verify with the ABF Working Tariff, USITC HTS, EU TARIC, and a licensed customs broker before import.

Office ESS 2 MWh — Australia: TCO Worked Example (rev 10)