In short: before you buy a battery to get round a grid limit, answer five questions in order. What does your load really look like? What does your tariff charge you for? How long is the connection delay really, and have you asked for a flexible connection? Could smarter charging do the job? Only then: what size of battery, and what will it save?
When a site cannot get the grid connection it wants, battery storage often looks like the obvious fix. Sometimes it is. But a battery is a significant investment, and it is easy to buy the wrong size, or to buy one when a cheaper fix was available. These are the questions we ask first.
1. What does your load really look like?
Everything starts with data. If your site has a half-hourly meter, you already have a year of readings showing exactly when you draw power and how much. For a new charging site, use session logs from similar sites or a realistic model of when vehicles will arrive and how much energy they will need.
Look for three numbers: your peak demand in kW, your average demand, and when the peaks happen. A site with short, sharp peaks and long quiet periods is a very different problem from one that runs hard all day.
2. What does your tariff charge you for?
Business electricity bills in Great Britain include network charges that depend on when and how you use power. Distribution charges use time bands. As Drax explains, a red unit rate applies during peak hours, usually 4pm to 7pm, with cheaper amber and green rates at other times. Larger sites also pay a daily charge for the capacity they have agreed with their network operator.
This matters because the value of a battery comes partly from what it avoids. If your peaks fall in the red band, shifting them to green hours saves money every day. If your agreed capacity is set for a rare peak, a battery that shaves that peak may let you agree a lower capacity. Check your own bill and your network operator’s charging statement, because bands and rates differ by region.
3. How long is the delay really, and is there another kind of connection?
Connection delays are real, but they are changing. Ofgem’s reforms removed stalled projects from the queue, and in December 2025 Ofgem said the queue had been reduced by nearly two thirds. Ask your network operator for a current, written view of when your connection could be delivered.
Ask too about connections that are not “firm”. A firm connection guarantees the full capacity at all times. A flexible connection lets the network operator limit your import at certain times, such as the evening peak, in return for an earlier or cheaper connection. Network operators offer these arrangements under different names, so ask what is available in your area. For an EV site that does most of its charging overnight, a connection limited at peak times may cost very little in practice.
4. Could smarter charging do the job for less?
Load management software shares the available power between chargers in real time. If ten vehicles plug in at once on a connection sized for five chargers at full power, each gets a share, and the total never exceeds the limit. For a depot where vehicles sit for hours overnight, this often solves the problem with no battery at all.
Smart charging works well when vehicles have time. It works less well when drivers need a fast charge and leave, which is where storage earns its place.
5. Only now: what size, and what will it save?
If the answers point to storage, size it from your peak-period energy and the time the battery has to refill. Our article on when battery-integrated fast charging makes sense walks through a worked example.
The cost side has improved sharply. BloombergNEF’s 2025 survey found that pack prices for stationary storage fell to $70 per kWh, 45% lower than in 2024. Pack prices are only part of a finished system’s cost, but the trend has changed the payback on many sites.
Count every benefit in the business case: avoided connection cost, earlier opening, lower peak charges, and any flexibility income. Then compare against the cheaper options above.
What to gather before you call anyone
| Information | Where to find it |
|---|---|
| Half-hourly consumption for 12 months | Your supplier or meter operator |
| Agreed supply capacity and tariff bands | Your electricity bill and contract |
| Current connection offer and date | Your network operator, in writing |
| Expected charging sessions and energy | Fleet plans, or data from similar sites |
| Space, access and planning constraints | Site plans and your local planning authority |
Frequently asked questions
Is battery storage always cheaper than a grid upgrade?
No. It depends on the upgrade cost, how long you would wait, and your load profile. For some sites a battery is clearly cheaper; for others a flexible connection or smart charging is cheaper still.
What is a flexible connection?
A connection where the network operator can limit how much power you draw at certain times, usually in return for connecting you sooner or more cheaply than a firm connection.
Can a battery reduce my capacity charges?
It can, if it reliably caps your peak demand. Talk to your supplier and network operator before you reduce your agreed capacity, and make sure the battery can cover the peak on your busiest days.
Working through these questions with real site data is what our solution recommendations service does. Send us your site details and we will tell you whether storage is the right answer.
