Batteries
Handing control of your battery to somebody else
Aggregators pay households to let a remote operator charge and discharge their storage on the network’s behalf, which is a real income and a real loss of control.
By Radhika Iyer3 min read
A fleet of small batteries behaves like one large one
Electricity networks need supply and demand to match continuously, and the services that keep them matched have traditionally come from large plant. A few thousand home batteries responding together can provide the same thing, provided somebody can dispatch them all at once and rely on them answering.
That somebody is an aggregator, and the arrangement is straightforward in principle. You allow remote control of some or all of your storage, the aggregator sells the resulting capability into whichever market pays for it, and you receive a share.
The services being bought are varied, and the language describing them is not standardised, which makes comparing two offers harder than it ought to be. Some schemes pay for the ability to respond within seconds to a frequency deviation on the network, others pay for a scheduled reduction in demand at a stated hour, and a few simply trade energy on your behalf. Each makes quite different demands on the battery.
It is a genuine service being genuinely paid for. It is not free money, and what you give up is worth understanding before signing.
What the household actually surrenders
The core of the deal is that the battery sometimes does what the operator needs rather than what your house needs. It may be discharged into the network on a winter evening when you would rather have kept it, or held full when your own strategy would have emptied it.
Contracts differ enormously in how much they take. Some claim only a slice of capacity and only during defined windows, leaving ordinary operation untouched the rest of the time. Others take broad control and run the battery to their own schedule, which can mean substantially more cycling than you would have chosen.
The number to look for is not the payment. It is how many events per year, how long each lasts, and how much capacity they may take.
Extra cycling has a cost that appears years later
Every discharge the aggregator commands is wear you did not schedule, and a battery worked harder reaches its warranty threshold sooner. That is not an argument against participating. It is an argument for reading the payment as compensation for consuming an asset rather than as pure income.
Warranties complicate this further, because some are expressed in total energy delivered rather than in years, and a heavily dispatched battery can exhaust such a warranty well before its calendar limit. A few manufacturers restrict or void cover for third-party control altogether.
Ask the manufacturer directly, not the aggregator. They are the party that will be asked to honour the warranty.
The arrangement suits some households and not others
The strongest case is a large battery in a household that rarely empties it, where the unused capacity is genuinely idle and someone is offering to pay for it. Sitting at full charge does the cells no favours anyway, so putting that capacity to work is not purely a sacrifice.
The weakest case is a battery already sized tightly against the evening, in a house that depends on it for backup. There the capacity is not spare, and handing it over means either accepting shortfalls or reserving so much that the payment shrinks to insignificance.
There is a middle position worth knowing about, in which the household keeps its own strategy and only the capacity above a set reserve is offered to the operator. That surrenders a great deal less and earns correspondingly less, and for a lot of people it is the sensible version of the arrangement rather than a compromise.
If you bought storage primarily to keep the lights on during outages, this probably isn’t for you.
Questions worth asking before signing anything
How much capacity can be taken and when. How many events per year are expected and what the maximum is. Whether you can opt out of an individual event, and what happens if you do so repeatedly. What notice period ends the contract, and whether any hardware or firmware change is required to join.
Also ask what happens to your own optimisation while the aggregator is in control, because the two strategies cannot both be running. Some arrangements hand the battery back between events. Others take it over completely, and the household strategy becomes irrelevant.
None of this makes participation a bad idea. It makes it a commercial arrangement to be read like one, rather than a feature to be switched on because the app offers it.
Common questions
Will the aggregator leave my battery empty when I need it?
A well-written contract sets a floor below which they cannot discharge, and reputable schemes do. A poorly written one may not, and this is precisely the clause to check before agreeing. If backup during outages matters to you, look for a guaranteed reserve rather than a promise of reasonableness.
Does joining a flexibility scheme void my warranty?
It can. Some manufacturers place limits on third-party dispatch or count the additional throughput against an energy-based warranty, and the answer differs between products. The aggregator is not the right source for this answer. Ask the manufacturer or check the warranty document, since they are the ones who decide a claim.
Can I take part without solar panels?
Usually yes, because what the network values is the ability to move energy in time, and that does not require the battery to have been charged from a roof. A grid-charged battery participating in flexibility markets is an ordinary arrangement, though the economics rest entirely on the payment terms and your tariff.
Features writer, Power Your Roof
Radhika writes about solar basics, batteries, bills & tariffs, mostly the parts other people skip and is unreasonably interested in the detail nobody else checks.
