Does your depot need a battery?
On-site battery storage (BESS) can cut your grid costs and even avoid an expensive connection upgrade — but it isn't right for every depot. Here's how to tell.
Last updated 15 August 2026
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Battery Energy Storage Systems — BESS — are one of the most misunderstood parts of depot electrification. They’re sometimes sold as essential and sometimes dismissed as a luxury. The truth is in between: a battery is a tool that solves specific problems, and whether it earns its place depends entirely on your site’s grid situation and tariff. Here’s how to work out if yours is a case for one.
What a depot battery actually does
A BESS charges up when power is cheap or plentiful and discharges when you need it. In a depot that unlocks three things: it can shave your peak demand (so you draw less power at once, cutting demand charges and sometimes avoiding a grid upgrade), it can shift energy in time (store cheap overnight power to use later), and it can provide resilience (keep critical charging running through a supply interruption). Different depots value these differently.
The strongest case: avoiding a grid upgrade
The most compelling reason to consider a battery is when your future charging peak exceeds your grid connection, and reinforcing that connection is slow or expensive. A battery can supply the extra power at peak by discharging, letting you run more chargers than your raw connection would allow — often at a fraction of the cost and time of a network upgrade. If your DNO has quoted a painful reinforcement figure, model a battery before you accept it.
The second case: cutting running cost
Even where capacity isn’t a problem, a battery can pay for itself by arbitraging price — charging when power is cheap and discharging to avoid buying at peak, and by trimming the demand charges tied to your peak draw. Whether this stacks up is a straightforward sum: the annual saving against the installed cost and the battery’s lifespan.
When you probably don’t need one
If your grid connection comfortably covers your peak, your vehicles all charge in the cheap overnight window anyway, and you’ve no particular resilience requirement, a battery may add cost without a clear return. Smart charging alone often captures most of the available saving. There’s no prize for over-engineering a depot.
Sizing, safety and second life
If the case is there, sizing is a balance — big enough to cover your peak-shaving or arbitrage need, not so big it sits half-used. Batteries carry real safety and siting requirements that belong in the design from the start, not bolted on. And second-life batteries (repurposed from vehicles) are an emerging, lower-cost option worth asking about.
The honest answer
A depot battery is neither essential nor pointless — it’s conditional. It shines when it lets you dodge a costly grid upgrade or when your tariff rewards shifting power around; it’s hard to justify when your connection is ample and your charging is already off-peak. Work out which camp you’re in before anyone quotes you for one.
Note: the current Depot Charging Scheme covers chargepoint and civil costs. On-site battery storage is not confirmed as an eligible cost under the scheme, so treat it as part of the wider project economics rather than assuming grant support.