Home batteries, two stacked revenue streams
Author
Volton Editorial Team
Date Published
A 10 kWh home battery in Estonia earns from two stacked revenue streams: ~€730/year from spot-price arbitrage alone, plus aggregated frequency-reserve revenue (only available via a BSP) that can roughly double the total. Stacked properly, the same hardware can clear above 10% IRR. Two streams, one battery, one customer connection.
A 10 kWh home battery cycled once a day at a €0.20 spread between cheap and expensive hours earns roughly €730 a year before efficiency losses. Same battery, same year, sitting idle on a wall as backup power: zero. The gap between those two outcomes is the entire economic case for residential storage in Estonia in 2025, and it gets wider when you stack a second revenue stream on top.
Stream one: spot-price arbitrage
Charge when the Nord Pool spot price is low, discharge when it is high. In an Estonian winter the day-night spread is routinely 5-10x, and even the duller shoulder seasons throw up €0.10 spreads on most days. Multiply by 365 cycles and a 10 kWh battery clears €365 to €730 a year on arbitrage alone, depending on how aggressively you trade and how volatile the year is.
Two caveats. Lithium-ion round-trip efficiency sits around 88-92%, so every kWh you discharge cost you roughly 1.1 kWh on the way in. Factor that into the spread math before getting excited. And arbitrage works much better when paired with rooftop solar: cheap morning generation goes into the battery, expensive evening demand comes out. Without solar, the case still works on pure grid trading, but the IRR drops a few points.
Stream two: aggregated frequency reserve
On its own, a 10 kWh battery cannot prequalify for Estonia's frequency reserve markets (FCR, aFRR, mFRR). The minimum bid sizes are too large and the telemetry requirements too strict. But pooled with hundreds of other homes by a Balance Service Provider, the combined virtual battery is large enough to qualify, and Elering pays capacity revenue for the time it stands ready, not just the energy it actually delivers.
Estonian mFRR prices have been structurally elevated since 2024, which means a household battery in an aggregator portfolio earns a meaningful share of that capacity payment every month. The deal is usually that the homeowner keeps a guaranteed slice (say 50%) reserved for backup and self-consumption, and the aggregator dispatches the rest.
Why stacking matters
At 2025 European installed prices (around €600/kWh for a typical home pack), pure spot-arbitrage on a 10 kWh battery comes in at roughly 5-9% gross IRR before degradation. Pure reserve participation through an aggregator lands at 5-10%, using far less cycle life since the battery mostly stands by rather than cycling deeply. Stacked together — and a battery sized so both streams fit — the combined IRR clears 10-15%. Without an aggregator licence in the mix, a home battery is half a battery economically: you only ever access one of the two markets it was built for.
Sizing, brands, and the boring details
For an Estonian household the sweet spot is 5-10 kWh. Smaller misses opportunities on the long winter evenings; larger ties up capital that struggles to pay back. Brands that integrate cleanly with local installers and aggregator platforms include BYD, Pylontech, Huawei LUNA2000, Solax Triple Power, Growatt and Tesla Powerwall. The 2026 net-metering rules tilt the math further in favour of self-consumption, which strengthens the case for buying sooner rather than waiting.
Backup power, by the way, is a nice-to-have rather than the main economic story. Most Estonian homes lose grid power for a handful of hours a year, and the battery handles that automatically as a side effect. Pair the battery with rooftop solar and the numbers improve again, because cheap self-produced kWh become the cheapest possible charging source.
Volton happens to be one of the few players in Estonia that runs both sides of this equation under one roof: Volton Home as the retail energy supplier and a BSP licence at Elering for the reserve markets. That is what lets a battery in the portfolio run arbitrage and frequency reserve at the same time, without the homeowner stitching together two contracts. Most of the savings stay with the customer; the rest pays for the platform that makes the second stream possible at all.
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