QDTB® Transformer

Diesel + Storage Peak Shaving Calculator

Enter peak and valley load to size the BESS, PCS and diesel backup, then compare pure grid, pure diesel and diesel+storage economics with a payback estimate.

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How peak shaving is sized

Shaving power = peak − valley load. The BESS is sized to that power for your shaving hours; the diesel genset backs it up. The ATS handles grid↔genset transfer, an optional STS serves sensitive loads, and DC/DC only applies to a DC-coupled PV-storage topology.

Worked Example — Diesel-Storage Peak Shaving

Example 1 — 500 kW Diesel-Storage Peak Shaving (4 h/day) · FOB $222,981
Diesel + storage peak shaving · 500 kW
2000 kWh BESS
500 kW PCS · 4 h/day · payback 2.3 yr
Daily saving
$260
Annual saving
$94,900
Est. BOM (FOB)
POA
📦 Bill of Materials
EquipmentModelSpecQty
Battery energy storage (BESS)2000 kWhLFP · 4 h discharge · peak shaving1
Power conversion system (PCS)500 kWbidirectional · grid-forming capable1
Diesel genset (backup)625 kVAbackup for BESS outage / extended peak · 500 kW1
ATS (grid ↔ genset)902 Aautomatic transfer · peak-shaving switching chain1
Static transfer switch (STS) · optional≤4 mssensitive-load static transfer (选配)1
Energy management system (EMS)EMSpeak-shaving dispatch · load forecast · SoC management1
Summary
Estimated total (FOB Qingdao, EXW) — priced equipmentPOA
💰 Three-option comparison (illustrative, annual)
OptionShaved energy costNotes
Pure grid$109,500/yrpay grid tariff for peak kWh (excl. demand charges)
Pure diesel$204,400/yrdiesel genset fuel at $0.28/kWh
Diesel + storage≈$138,488/yrvalley charging + BESS amortised (CRF 13%)
📐 Peak-shaving curve
BESS500 kW / 2000 kWhPCS500 kW
LEGENDBreaker (52)kWhMeter (kWh)SPD (surge protection)
📏 Standard basis
TopicStandard
Storage interconnectionGB/T 36547 — electrochemical energy storage connecting to power grid
EES systemsIEC 62933 — electrical energy storage systems
GensetISO 8528 — generating sets
🧮 How it was calculated
1. Shaving power = 1000 − 500 = 500 kW
2. BESS energy = 500 kW × 4 h = 2000 kWh
3. PCS = 500 kW · diesel backup = 625 kVA (500 kW)
4. Daily shaved energy = 500 × 4 = 2000 kWh/day
5. Spread = diesel $0.28 − grid $0.15 = $0.130/kWh → daily saving $260
6. Payback = BESS CAPEX $222,981 ÷ annual saving $94,900 = 2.3 years
📋 Design notes
Economics basis (illustrative): Savings assume the BESS charges at the grid price and discharges to displace diesel generation (or a higher peak tariff) at the 0.130 $/kWh spread. Actual payback depends on demand-charge structure, TOU tariffs and cycle life — verify with the local tariff.
Three-option comparison: Pure grid $109,500/yr vs pure diesel $204,400/yr vs diesel+storage ≈$138,488/yr for the shaved energy — storage wins where the spread is large and daily cycling is regular (illustrative, excludes demand-charge savings).
Pricing basis: BESS and PCS priced per kWh/kW from the catalogue; diesel genset and ATS from their price references. STS (sensitive loads, ≤4 ms) and EMS are optional and quoted per project (POA).
Switching chain: The ATS handles grid↔genset transfer; an optional static transfer switch (STS) provides ≤4 ms break-free transfer for sensitive loads; DC/DC converters are only needed for a DC-coupled PV-storage topology (not this AC peak-shaving case).
Design review: This is a preliminary sizing. Verify the load profile, demand-charge rules, BESS cycle life at the target DoD, and local interconnection/fire-safety codes.

How it was calculated

Core formulas

Shaving power = peak − valley. BESS energy = shaving power × hours. Saving = shaved energy × (diesel − grid) spread. Payback = BESS CAPEX ÷ annual saving.

Applicable standards

GB/T 36547 (storage interconnection), IEC 62933 (EES systems), ISO 8528 (gensets).

Frequently asked questions

How does the payback work?

The BESS charges at the grid price and discharges to displace diesel (or a higher peak tariff). Payback = BESS CAPEX ÷ annual saving, driven by the diesel−grid spread and daily cycling.

What is the switching chain?

An ATS switches between grid and genset; an optional static transfer switch (STS, ≤4 ms) serves sensitive loads; DC/DC converters are only needed for DC-coupled PV-storage, not this AC case.

Which three options are compared?

Pure grid (buy peak kWh at the grid tariff), pure diesel (fuel at the diesel rate), and diesel+storage (valley charging plus amortised BESS). Storage wins where the spread is large and cycling is regular.

What is priced in the BOM?

BESS and PCS (per kWh/kW) and the genset + ATS are priced from the catalogue. The STS (optional) and EMS are quoted per project.

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Results are engineering estimates for reference. Final design must be confirmed by a licensed local engineer against site conditions and applicable codes. Prices are FOB Qingdao (EXW) and do not include freight, duty or installation.

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