Battery ArbitrageBESS
Battery arbitrage is charging a battery when electricity is cheap and discharging it when power is more valuable. Profit depends on the price gap and the round-trip efficiency — the share of stored energy that comes back out, often around 85–90% for lithium-ion systems.
Power is cheap at some hours and expensive at others. A battery can buy the cheap hours and sell the expensive ones, but every cycle loses some energy, so the spread has to beat the losses.
- Category
- Commodities, Energy and Carbon
- Reading time
- 4 min
- Also called
- Energy arbitrage, Storage arbitrage, Battery time-shifting
- Updated
Battery arbitrage in plain words
Stored electricity may be sold at a premium above the price of the charging electricity — EIA calls this arbitrage.1
Storage always uses more electricity to charge than it gives back when discharging.1
Round-trip efficiency is the share of electricity put in that is later retrieved; NREL's 2025 baseline assumes 85% for utility-scale batteries.2
How a battery arbitrage trade works
Forecast prices
Identify low-demand hours to charge and high-demand hours to discharge.1
Know your efficiency
Use output divided by input as the round-trip efficiency.2
Compute the break-even spread
Sell price must exceed buy price ÷ efficiency, because higher efficiency means less energy lost.3
Charge
Buy power in the cheap window.
Discharge
Sell or use the stored power when prices are higher.1
Review real efficiency
Compare with measured values: EIA found the US battery fleet averaged 82% monthly.3
Worked examples
Example 1 — A profitable cycle
+$480 per cycleA hypothetical 10 MWh charge at $20/MWh, sold at $80/MWh, with 85% round-trip efficiency.
| Charging cost | 10 × $20 = $200 |
| Energy out | 10 × 0.85 = 8.5 MWh |
| Revenue | 8.5 × $80 = $680 |
| Gross margin | $680 − $200 = $480 |
The margin exists only because the discharged power sells at a premium above the charging cost.1
Example 2 — Spread too small
−$17.50 per cycleSame battery, charge at $40/MWh, sell at $45/MWh.
| Charging cost | 10 × $40 = $400 |
| Revenue | 8.5 × $45 = $382.50 |
| Result | $382.50 − $400 = −$17.50 |
Because storage uses more electricity to charge than it returns, a small spread loses money.1
Example 3 — Break-even sell price
Break-even ≈ $35–37/MWhCharge at $30/MWh with 85% efficiency.
| Break-even | $30 ÷ 0.85 = $35.29/MWh |
| At 82% efficiency | $30 ÷ 0.82 = $36.59/MWh |
| Extra spread needed | $36.59 − $35.29 = $1.30 |
Using EIA's measured 82% fleet average instead of the 85% assumption raises the hurdle.3
Battery arbitrage vs financial spread trading
| Aspect | Battery arbitrage | Financial spread trade |
|---|---|---|
| What you trade | Physical energy across hours | Contracts across dates or markets |
| Main loss | Round-trip efficiency and degradation | Fees and adverse moves |
| Capacity limit | Battery MWh and power rating | Margin and liquidity |
| Price risk | Spread may not appear | Spread may widen against you |
Where battery arbitrage is used
Solar-heavy grids
Charge at midday, discharge at evening peaks.
Price spikes
Capture short Volatility bursts.
Negative prices
Get paid to charge in some hours.
Revenue stacking
Combine with grid services to improve returns.
Advantages and disadvantages
Advantages
- Profits from predictable daily price shapes.
- Can flatten peaks and support the grid.
- Fast response to price spikes.
Disadvantages
- Efficiency losses eat into every cycle.
- Spreads shrink as more batteries compete.
- Battery degradation adds hidden costs.
- Forecast errors can turn cycles into losses.
Going deeper
Read as far as you need. Each level builds on the one before it.
Buy low, sell high
Beginner
Charge in cheap low-demand hours, discharge in expensive high-demand hours.1
Efficiency math
Intermediate
Round-trip efficiency is output over input; the sell price must beat buy price ÷ efficiency.2
Assumed vs real
Advanced
Planning models assume 85%, but measured fleet averages were 82%, so stress-test with lower values plus degradation.2
Common mistakes
Ignoring losses
Using the raw price spread as profit.
Optimistic efficiency
Using spec-sheet figures, not measured ones.
Over-cycling
Wearing the battery for tiny spreads.
Static forecasts
Assuming yesterday's price shape repeats.
Check your understanding
Test yourself before moving on. Each answer comes with an explanation.
Key points to remember
- Battery arbitrage buys cheap hours and sells expensive ones.
- Round-trip losses mean you sell less than you buy.
- Break-even sell price = buy price ÷ efficiency.
- Planning assumptions near 85% may exceed real results.
- Competition and degradation shrink returns.
Frequently asked questions
Is battery arbitrage the same as a CFD trade?
Why don't batteries return all the energy?
Can home batteries do arbitrage?
Further learning
- Break-Even
Working out the minimum spread.
- Volatility
Why price swings create opportunity.
- Spot Trading
How spot power is bought and sold.
- Hedging
Locking in prices ahead of time.
Sources
This article is written in our own words. The sources below support the specific facts, rules and figures marked with a number in the text. Links open the original publisher’s page.
- U.S. Energy Information Administration. Energy storage for electricity generation (opens in a new tab) Checked .
- National Renewable Energy Laboratory (ATB). Utility-Scale Battery Storage – 2025 Annual Technology Baseline (opens in a new tab) Checked .
- U.S. Energy Information Administration. Utility-scale batteries and pumped storage return about 80% of the electricity they store (opens in a new tab) Checked .
Educational content, not financial advice. Examples use hypothetical prices and simplified costs; actual fees, margin rules and regulations vary by broker, market and country. We are not affiliated with any publisher linked above. Last reviewed . Report an error or request a source credit.