Energy Arbitrage vs Peak Shaving: What's the Difference for Home Batteries?

If you've been researching home battery storage, you've almost certainly encountered both terms. Sometimes they're used interchangeably. Sometimes they're presented as competing strategies. Neither is quite right - and the confusion costs people with batteries real money, because not understanding the difference makes it harder to know which tariff to choose and whether your battery is actually working for you.

This article lays out what each term means, where they overlap, which UK tariffs support which strategy, and what the numbers actually look like before you factor in battery wear.

Note: This article focuses on UK electricity tariffs and pricing. The underlying concepts - energy arbitrage and peak shaving - apply globally, but specific tariff names, rate windows, and unit prices vary by country. All figures were verified at the time of writing (May 2026) and are subject to change; always confirm current rates with your energy supplier before making financial decisions.

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What Is Energy Arbitrage for Home Batteries?

Energy arbitrage is the act of buying cheap, selling (or using) expensive. For a home battery, that means charging when electricity is cheap - typically overnight on a time-of-use tariff - and then either using that stored energy or exporting it when prices are higher.

The profit isn't cash in hand (unless you're exporting). It's avoided expenditure: you never had to buy that expensive peak-rate electricity because you already had it stored in your battery at a fraction of the cost.

Self-consumption arbitrage (no export required)

This is the most common form for UK battery owners and the one that gets least airtime. You charge your battery overnight at a cheap rate, and during the day - when the grid rate is higher - your home draws from the battery instead of the grid. No export, no smart meter export MPAN required.

The saving is the difference between what you would have paid from the grid and what you actually paid to charge the battery (adjusted for efficiency losses - more on those below). On Intelligent Octopus Go at 8p/kWh overnight (Octopus Energy, verified May 2026) versus the standard 24.67p/kWh daytime rate (Ofgem unit rate price cap, April–June 2026), that spread is meaningful.

Export arbitrage

Export arbitrage takes self-consumption a step further. When your stored energy (or real-time solar generation) is worth more per kWh exported than it cost to generate or charge, you export it during the expensive window. Octopus Flux's three-rate structure - with a distinct export rate during the evening peak - is designed specifically around this.

Export arbitrage requires a compatible inverter with export metering, an export MPAN, and on Flux, MCS-certified solar PV. That's a meaningful additional barrier to entry compared with self-consumption arbitrage.

The efficiency and wear costs you must account for

No battery is 100% efficient. Modern lithium-ion systems - including the FoxESS range common in UK residential installs - achieve around 90% round-trip efficiency (RTE). That means for every 10 kWh you push in, roughly 9 kWh comes back out.

The practical consequence: divide your charge rate by 0.9 to find the true effective cost of stored energy. Charging at 8p/kWh overnight on Intelligent Octopus Go means your usable electricity actually costs 8.9p/kWh - not 8p. Every arbitrage calculation needs to start here, not at the nominal cheap rate.

There's also battery degradation. Every charge-discharge cycle uses a small fraction of the battery's rated cycle life. Depending on the cost of your battery and its rated cycle count, this adds roughly 5–10p per kWh cycled. Arbitrage that looks profitable on a spreadsheet before wear cost can look a lot thinner afterwards.

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What Is Peak Shaving for Home Batteries?

The commercial definition (demand charges - not relevant for UK homes)

In a commercial or industrial setting, "peak shaving" has a precise meaning: reducing the maximum kilowatt draw during a billing period to avoid demand charges. Many commercial tariffs bill partly on the single highest 15-minute or 30-minute power draw in a month. A large battery that activates during that spike can save thousands of pounds in demand charges alone. This definition is entirely irrelevant to UK residential electricity customers, who don't pay demand charges.

The residential definition (avoiding peak-rate imports)

For households, peak shaving means something subtler but still genuinely valuable: using your battery to cover home consumption during the periods when grid electricity costs the most, so you import as little as possible during those expensive windows.

On Octopus Flux, that's the 16:00–19:00 peak window. On Economy 7, it's the daytime period (often above the standard variable tariff rate - making daytime battery discharge more valuable than people expect). On Octopus Agile, it's whatever half-hours are priced highest on any given day.

The goal is straightforward: when the grid is expensive, don't use it. Use the battery instead. That's residential peak shaving.

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Arbitrage vs Peak Shaving - Side-by-Side

Dimension	Energy Arbitrage	Peak Shaving
Primary goal	Maximise price spread between cheap and expensive periods	Eliminate or reduce grid draw during high-cost peak windows
Best tariff type	Time-of-use or dynamic pricing with wide spread	Any tariff with a distinct expensive period
Solar required?	No	No (but solar amplifies both)
Export required?	Only for export arbitrage - self-consumption arbitrage needs none	No
Optimisation complexity	High - needs price, solar, and load forecasting	Low - a fixed schedule captures most value

The key observation from this table: arbitrage tends to care about maximising the spread, while peak shaving cares about not drawing from the grid during specific windows. On most real tariffs, those two objectives point the battery in exactly the same direction.

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They're Not Mutually Exclusive - Here's Why They Compound

A battery that charges at 02:30 on Octopus Flux and discharges from 16:00–19:00 is simultaneously:

• Doing energy arbitrage: it captured cheap overnight electricity and avoided buying expensive peak electricity, capturing the price spread as a saving.
• Doing peak shaving: it powered the home during the most expensive window, preventing grid imports at the peak rate.

These aren't two separate strategies requiring two separate batteries. They describe the same physical action from two different angles. The commercial and academic literature tends to distinguish them because the optimisation objectives differ at scale - commercial peak shaving targets kW demand, residential arbitrage targets kWh price spread. But for a household with a FoxESS or similar inverter on a time-of-use tariff, the schedule that maximises arbitrage and the schedule that maximises peak shaving are usually identical.

Where they can diverge: if your battery is undersized and you have to choose between charging deeply overnight (maximising arbitrage spread) versus leaving headroom for solar self-consumption, the two objectives start to trade off. A 5 kWh usable battery on a high-consumption household may need careful scheduling to do both well.

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Which UK Tariffs Support Each Strategy?

Tariff	Cheap window	Peak/expensive window	Best for	Solar/export needed?
Octopus Flux	02:00–05:00	16:00–19:00	Both arbitrage + peak shaving	Yes (solar + export MPAN) - currently on pause
Octopus Agile	Dynamic (typically overnight lows)	Typically 16:00–19:00+	Arbitrage (dynamic)	No
Intelligent Octopus Go	23:30–05:30 at 8p/kWh	All other hours at ~24.67p/kWh	Self-consumption arbitrage	No (but requires EV + compatible charger)
Economy 7	~7h overnight (check with supplier)	Daytime (often above SVT rate)	Both (more modest spread)	No

A few points worth flagging:

Octopus Flux is the strongest tariff for combined arbitrage and export - but it is currently on pause and expected to return. It requires solar PV with MCS certification and an export MPAN. Do not sign up expecting to access it immediately.

Intelligent Octopus Go at 8p/kWh overnight is an excellent self-consumption arbitrage tariff, but it is not available to battery-only households without an EV. The eligibility requirement is a compatible smart charger, not solar.

Octopus Agile is the most sophisticated - and most volatile - option. Half-hourly dynamic pricing means the optimal charge window changes daily and can occasionally go negative (the grid pays you to consume). This is where fixed schedules fall apart and forecasting genuinely earns its keep.

Economy 7 is often underestimated. The daytime rate on E7 is frequently above the standard variable rate, which makes discharging into daytime consumption more valuable than a headline cheap rate comparison suggests. Worth running the numbers with your actual meter readings.

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3 Common Misconceptions Debunked

1. "You need export capability to do energy arbitrage."

False. Self-consumption arbitrage - charging cheap overnight and using that stored energy instead of buying expensive grid electricity during the day - is full energy arbitrage. Export is one type of arbitrage. It is not the definition of it. Many UK battery households do energy arbitrage without earning export energy.

2. "Peak shaving is only for businesses."

The commercial definition (avoiding demand charges on maximum kW draw) is indeed irrelevant for UK residential customers. But the residential equivalent - discharging your battery during the most expensive rate window to avoid costly grid imports - is genuine peak shaving, it delivers real savings, and it applies to any household on a tariff with a distinct expensive period. The mechanism is the same; the tariff structure is different.

3. "Arbitrage and peak shaving conflict with each other."

On the contrary, they describe the same physical action from different angles. A battery charged at 03:00 and discharged at 17:00 is simultaneously capturing a price spread (arbitrage) and eliminating peak-rate grid draw (peak shaving). There is no conflict. Where trade-offs do arise - for example, leaving battery headroom for solar versus maximising overnight charge - those are scheduling constraints, not a conflict between the two strategies.

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Is Energy Arbitrage Worth It for a UK Home Battery?

The honest answer is: it depends on your tariff, battery size, and usage pattern. But it's worth running the numbers clearly, so here are two illustrative scenarios.

These are illustrative calculations only, using assumptions stated below. They are not a guarantee of savings or a quote.

Scenario 1 - Intelligent Octopus Go (self-consumption arbitrage)

• Charge rate: 8p/kWh overnight
• Effective stored cost (8p ÷ 0.9 RTE): 8.9p/kWh
• Avoided daytime import rate: 24.67p/kWh (Ofgem price cap, April–June 2026)
• Gross spread per usable kWh: 24.67p − 8.9p = ~15.8p/kWh
• Usable discharge per day: 5 kWh
• Gross annual saving: 5 kWh × 15.8p × 365 = ~£288/year
• Battery wear (5 kWh × 7.5p × 365): ~£137/year
• Net annual saving (illustrative): ~£151/year

Scenario 2 - Flux-style three-rate tariff (illustrative only - not current Flux rates)

Assuming round-number illustrative rates of 12p off-peak and 35p peak avoided:

• Effective stored cost (12p ÷ 0.9 RTE): ~13.3p/kWh
• Gross spread per usable kWh: 35p − 13.3p = ~21.7p/kWh
• Gross annual saving: 5 kWh × 21.7p × 365 = ~£396/year
• Battery wear (5 kWh × 7.5p × 365): ~£137/year
• Net annual saving (illustrative): ~£259/year
• Subtract any export foregone or solar trade-offs: figures vary

The wear cost - roughly 5–10p/kWh depending on your battery's purchase cost and rated cycle life - is the variable most people ignore. It matters most when the arbitrage spread is modest. On a tariff with a thin spread, the battery may cycle at a loss.

A minimum viable battery size for meaningful arbitrage is around 5 kWh usable - enough to cover a typical evening peak window. Ten kilowatt-hours gives comfortable headroom. Thirteen to fifteen kilowatt-hours unlocks meaningful solar export opportunity on dynamic tariffs.

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How Automation Makes the Difference

On a structured time-of-use tariff - where peak and off-peak windows are fixed, as on Octopus Flux or Economy 7 - a static schedule (charge overnight, discharge at peak) can serve as a useful starting point. But even on a tariff as regular as Flux, a fixed schedule leaves real value on the table. Solar output changes day by day: on a sunny day your panels may fill the battery well before the evening peak, making overnight grid charging unnecessary. Household demand varies too: a high-usage evening may warrant a deeper overnight charge than a quiet one. Without adapting to daily solar and load conditions, a static schedule will routinely either over-charge or under-charge, and the gap between 'adequate' and 'optimal' compounds over time.

Octopus Agile is where fixed schedules break down entirely. The cheapest half-hours shift nightly based on wholesale markets. Some nights have four genuinely cheap hours; others have one. Prices occasionally go negative. A fixed schedule either misses the cheapest window or charges at hours that turn out not to be cheap. The value left on the table is real.

Solar adds another layer. On a sunny day, charging overnight is unnecessary - your panels will fill the battery by mid-morning. But a fixed schedule doesn't know that, so it charges anyway, and when solar generation arrives it finds a full battery and is forced to export immediately at whatever the current rate happens to be - rather than being held and exported during the peak window when the rate is highest. The result is both wasted overnight charging cost and foregone peak export revenue.

Doing this well requires three inputs working together: a solar generation forecast, a load prediction for the coming day, and the actual tariff prices - combined into a schedule that maximises the spread after accounting for round-trip efficiency and battery wear. Mathematical optimisation handles this class of problem efficiently, finding the globally optimal charge-discharge schedule rather than a heuristic approximation.

BatteryWiz does exactly this - pulling Solcast solar forecasts, predicting household load, and running a mathematical optimisation every 30 minutes so your battery is always optimally adapted to changing situations throughout the day. If you'd like to try it, you can download BatteryWiz here.

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Sources: Octopus Energy product page (Intelligent Octopus Go rate of 8p/kWh, verified May 2026); Ofgem price cap determination (unit rate 24.67p/kWh, April–June 2026 quarter). Illustrative savings calculations assume 5 kWh discharged per day, 365 days per year, at a battery wear cost of 7.5p/kWh cycled.