Batteries for ancillary services: how batteries earn on reserves

A battery selling ancillary services earns money on its response capability: Energinet pays for reserves that can stabilise the grid frequency at 50 Hz, and nothing else on the grid responds as fast as a battery. That goes for industrial-scale battery plants and home batteries alike — the difference is that a home battery must be pooled with others in a virtual power plant to be big enough for the market. What ancillary services are, and which types exist, is explained on the ancillary services page — here we look closer at the battery’s role.

Why are batteries so well suited to ancillary services?

Grid reserves are organised by speed: the fastest must respond automatically within seconds when the frequency deviates, while slower reserves take over after minutes and restore the balance. The faster and more precisely a unit can respond, the more valuable it is at the fast end — and that is exactly where batteries belong:

• Response time in seconds. A battery can go from idle to full power — or change direction — almost instantly.
• Both directions. It can deliver power to the grid (up-regulation) and absorb power from it (down-regulation). Most other reserves can only do one of the two.
• Precision. Output can be dosed exactly, which makes documenting the delivery simple.

NM1 bids households’ batteries in as FCR-D — the fast frequency reserve Energinet buys in daily auctions, one for every hour of the day.

What does it take to participate?

Energinet’s markets have requirements for size, documentation and prior approval of the unit. A single home battery cannot meet them alone — and that is precisely the aggregator’s role: orchestrating many batteries into one virtual power plant that plays in tune with the grid, and handling approval, bidding, documentation and revenue sharing. NM1 has been live since June 2025. The background on why the grid buys reserves at all is in the article on grid balancing.

For you as a battery owner, the requirements are simple by comparison: a compatible inverter that supports remote control — integration happens through the inverter manufacturers, including Solplanet — and stable wifi, typically 2.4 GHz.

How is the battery bid in, in practice?

The auctions clear the day before, hour by hour, so the control system must know what the battery can deliver tomorrow. NM1 predicts the battery’s state of charge and bids asymmetrically around it: a battery standing full after a sunny day is bid only in the “deliver to the grid” direction; a nearly empty one in the “absorb” direction; a half-charged one can respond both ways. We only bid in when doing so is worth more than not doing so — the battery’s other jobs, such as solar self-consumption, continue essentially as before. The details are in the article on a battery for solar panels — and if you don’t have solar, it doesn’t matter: the reserve sells independently of the sun, as explained in the article on a battery without solar.

The activations themselves are short — seconds to minutes — and come in bursts: some days 5–6 of them, then perhaps ten days without, on average a few per week. Most of the time the reserve simply stands ready, and that readiness is what Energinet pays for.

What does the battery earn?

FCR-D prices are set in the daily auctions and vary with the market — past earnings are no guarantee of future earnings. Revenue is shared between you and NM1 and paid out quarterly as an ordinary bank transfer — behind the scenes, NM1 is settled via eSett, the joint Nordic settlement of the balancing markets. You follow the battery’s activations and your payouts in the web app, and how earnings are calculated is shown on the earnings page.

If you already own a compatible battery, signing up is free — see which batteries and inverters we can connect, or start on the get started page.