Battery storage payback for Vietnam.
Enter your EVN tariff and monthly consumption. We size a behind-the-meter battery, compute arbitrage revenue, and show payback and IRR under self-invest and bank-financed cases. Budget-level — precise numbers come after a site survey.
Enter your tariff and consumption.
Results update in real time as you type.
Power = 80% × average load during peak tariff hours in your lowest-consumption month. Energy = power × 2 hours. Conservative by design — no overshooting lowest-season demand.
Cashflow profile — unlevered
Cashflow profile — levered (after debt service)
Gearing sensitivity
Why these numbers are conservative
The model runs one cycle per day — charging at off-peak (00:00–06:00) and discharging across the new 5-hour continuous evening peak (17:30–22:30 Mon–Sat). This reflects Decision 963/QÄ-BCT, which landed on 22 April 2026 and abolished the morning peak window (09:30–11:30) and the pre-22:30 evening peak. With no morning peak to arbitrage and the standard-rate band too close to off-peak to drive a second cycle economically, single-cycle dispatch is now the default. The dual-cycle apparatus is preserved in the Advanced panel — if peak-hour rules change again, set Phase 1 cyc/day to 2 and Phase 1 years to 3 to model a two-cycle scenario.
Vietnam’s new two-component tariff — separating a capacity charge (by registered peak kW) from an energy charge (by actual kWh) — rolls out to manufacturing pilot customers from July 2026 (≥200,000 kWh/month, ≥22 kV). We assume the same framework extends to business tariff customers (hotels, data centres, showrooms) within a few years. From Year 4 of the model (default two-component intro year), we apply a 20% compression to the peak/off-peak spread — a conservative forward view of how the energy-charge component will flatten as the capacity charge takes more of the bill.
Under the two-component tariff, your bill splits into a capacity charge (Cp × Pmax) and an energy charge. BESS shaves your monthly peak demand and cuts the capacity charge directly — a separate revenue stream on top of the arbitrage we’ve calculated. We deliberately exclude this from the headline numbers because it depends on your site’s Pmax pattern, which only a load analysis can quantify. Treat it as upside.
Frequently asked
What is the two-component tariff?
The two-component tariff replaces Vietnam's current single-charge electricity bill with two separate components: a capacity charge (Cp × your registered peak kW) and an energy charge (Ca × actual kWh consumed). The capacity charge reflects the fixed infrastructure cost of supplying power to you; the energy charge reflects the variable cost of the electricity you actually use.
The tariff is mandated by Article 50 of the amended Electricity Law 2024 and Government Decree 146/2025/NĐ-CP. A paper-based pilot ran from January 2026, with live billing starting July 2026 for manufacturing customers consuming at least 200,000 kWh/month at 22 kV or above. Broader rollout is expected through 2028–2030.
What's the difference between a single and double cycle per day?
With one cycle, the battery charges once at off-peak (00:00–06:00) and discharges once across the evening peak (17:30–22:30 Mon–Sat). With two cycles, it would charge and discharge twice in 24 hours, capturing a second arbitrage window. Two cycles generate more revenue per day but consume two of the 8,000 warranted cycles, halving useful battery life.
The model defaults to one cycle per day. On 22 April 2026, MOIT issued Decision 963/QÄ-BCT, abolishing the morning peak window (09:30–11:30) and consolidating the evening peak into a single 5-hour continuous block (17:30–22:30 Mon–Sat, no peak Sunday). With no morning peak, there is no second high-spread window to arbitrage — the standard-rate band sits too close to off-peak to drive a second cycle economically. Single-cycle dispatch is now the operational default and also extends useful battery life.
The dual-cycle apparatus is preserved in the engine. If TOU rules change again or you want to model a hypothetical, set Phase 1 cyc/day to 2 and Phase 1 years to 3 in the Advanced panel — the model will compute a two-cycle scenario for those years exactly as before.
Source: Decision 963/QÄ-BCT (22 April 2026) — TOU window restructure
What is Pmax and how does BESS affect it?
Pmax is the highest 15-minute average demand (kW) recorded in a billing period. Under the two-component tariff, your capacity charge is Cp × Pmax every month, regardless of when the peak occurs. A BESS dispatched to shave that peak cuts Pmax directly — and the capacity charge falls by the same percentage.
For a factory with a 2 MW Pmax paying the current pilot capacity rate of VND 235,414/kW/month (22–110 kV), a 400 kW shave is worth roughly VND 94 million/month (~$3,700). We exclude this from the calculator headline because only a site-specific load analysis can tell you the realistic shave potential.
Which EVN decision sets the current tariff?
Decision 1279/QĐ-BCT dated 9 May 2025, effective 10 May 2025. Average retail price is VND 2,204.07/kWh excluding VAT. Full TOU tariff tables (by voltage level and customer class) are used directly in this calculator.
How is the battery sized from my bill?
We take the average load during peak tariff hours in your lowest-consumption month, multiply by 0.80 to get BESS power in kW, and multiply that by 2 hours to get BESS energy in kWh. Sizing to the lowest month guarantees the battery is fully utilised every month of the year — no oversized capacity sitting idle in your low season.
Peak hours per month are calculated from the EVN TOU schedule: Mon–Sat have 5 peak hours per day (17:30–22:30, continuous), Sundays have no peak hours under Decision 963/QÄ-BCT. With roughly 26 peak days per month, that's ~130 peak hours.
Why does the calculator show a compression effect even for business tariffs not in the pilot?
Because we believe the two-component framework will extend to business tariff customers within a few years, we bake the 20% spread compression into all scenarios from Year 4. This is a deliberate conservatism: if the two-component tariff doesn't apply to your tariff class, your actual post-Year-4 revenue will be higher than shown. If it does apply, we've already modelled the headwind.
Method — full calculation detail
Sizing
Battery is sized to 80% of the average load during peak tariff hours in your lowest-consumption month, with a fixed 2-hour discharge duration. Guarantees full utilisation every month of the year.
Revenue
One cycle per day: charge at off-peak (00:00–06:00), discharge across the evening peak (17:30–22:30 Mon–Sat), arbitraging the peak/off-peak spread. Battery capacity degrades 2% in Year 1 and 2.5% per year thereafter. The dual-cycle apparatus remains available via the Advanced panel: setting Phase 1 cyc/day to 2 reactivates Cycle 2 (peak versus standard) for the configured Phase 1 years.
Tariff escalation
Before the two-component tariff applies: all rates escalate at 5% p.a. At Year 4 (assumed two-component intro), the peak/off-peak spread compresses 20%. After intro: the spread escalates at 5% for 3 years, then 3% thereafter.
Debt mechanics
Equal-principal amortisation over loan tenor. Interest charged on opening balance. DSCR = EBITDA / debt service. Tax on EBIT after interest and depreciation.