We are being asked about commercial battery storage on almost every large commercial solar project we look at now.
Whether we’re talking to a business, school, farm or NHS site, the question is usually the same: “Should we add batteries?”
A few years ago, the answer was often no. Commercial batteries were expensive and, unless there was a specific reason for installing one, the payback could be difficult to justify.
That’s changing quite quickly.
Battery prices are coming down, electricity tariffs are becoming more sophisticated, and modern energy management systems give us much greater control over when a business imports, generates, stores and uses electricity.
More importantly, we’re no longer looking at a commercial battery simply as somewhere to put excess solar.
On the right site, it becomes part of the electrical infrastructure – moving electricity away from expensive periods, reducing peak demand, supporting EV charging and providing backup for critical systems.
But that doesn’t mean a battery makes sense everywhere.
A commercial battery is really about moving energy
At its simplest, a battery allows us to move electricity from one time of day to another.
If a solar PV system produces more electricity than the building can consume, we can store that surplus and use it later rather than exporting it to the grid.
That’s the traditional argument for business solar battery storage installation, but on larger commercial sites it can be only one part of the calculation.
A battery can also charge from the grid when electricity is cheaper and discharge when electricity is expensive.
This means businesses can potentially reduce electricity costs with battery storage even when they don’t have large amounts of surplus solar.
The key is understanding when the site actually uses electricity and what it costs at those times.
It’s not just about storing surplus solar
One of the biggest misconceptions about commercial batteries is that their main purpose is to store excess solar.
For many commercial sites, the bigger opportunity can be changing when the business purchases electricity from the grid.
Depending on the supply contract and network charging arrangements, electricity consumed during certain periods can be considerably more expensive.
A battery gives us the ability to shift some of that demand.
We recently modelled this on a large commercial site using half-hourly electricity data. Its normal consumption profile showed significant electricity purchases throughout the working day, including during the higher-cost periods.
We then modelled the effect of a 10MWh battery.
The site’s underlying energy requirement hadn’t disappeared. Instead, the battery allowed much more electricity to be purchased outside the higher-cost energy transmission periods, stored and then used during the working day.
When solar PV and battery storage were modelled together, the principle became even more interesting. Solar could supply part of the daytime load, the battery another part, with the remaining grid electricity potentially shifted predominantly into off-peak periods. The feasibility study deliberately did not include the additional benefit of a dual tariff at that stage because it had not yet been quantified.
So rather than simply asking:
“How much spare solar have we got to put into a battery?”
We increasingly ask:
“When are you buying electricity, what is it costing you at those times, and can we use solar and storage to change that?”
For a high-consumption business, that can be a much more valuable question.
Commercial battery storage and peak shaving
Another important application is peak shaving.
A commercial building might have a fairly consistent electrical demand for most of the day but experience much larger peaks when several pieces of equipment operate together.
A correctly designed battery can supply some of that additional demand instead of taking all of it from the grid.
Depending on the site’s tariff and electrical infrastructure, reducing those peaks can lower costs and, in some circumstances, help avoid or delay an expensive upgrade to the incoming electricity supply.
We’re seeing this become increasingly relevant as businesses add EV charging, heat pumps and other large electrical loads.
Instead of treating solar, batteries, EV chargers and the incoming supply as completely separate systems, we increasingly design them as one energy system.
What if a business already uses nearly all its solar?
This is where proper battery modelling becomes important.
One of our recent commercial feasibility studies looked at approximately 1.2MWp of proposed solar PV on a site consuming around 6GWh of electricity each year.
Initial modelling suggested around 99.1% of the solar electricity could be consumed on site, with only around 11.45MWh exported annually. Solar would provide approximately 21.2% of the site’s annual electricity requirement.
If you looked purely at surplus solar, you could quite reasonably ask why the site needed a battery at all.
But that’s missing the bigger opportunity.
With significant grid consumption remaining, battery storage could be considered as a way of changing when those remaining megawatt-hours are purchased, rather than simply storing the relatively small amount of surplus solar.
That’s why we don’t size commercial batteries purely against the solar array.
Battery storage can also provide site backup
Cost saving isn’t always the only reason for installing a battery.
For some businesses, the cost of losing power for an hour can be considerably greater than the cost of the electricity itself.
A correctly designed commercial battery backup system can keep critical parts of a site operating if the grid fails.
That might include refrigeration, IT and communications, security systems, pumps, controls, production equipment or other essential plant.
For some sites, full-site backup may be appropriate. For others, it makes far more sense to identify the genuinely critical systems and design an essential-load arrangement that the battery can support for a defined period.
In our recent commercial feasibility work, the example 10MWh BESS specifically included full-site backup as part of the proposed concept. But backup has to be designed properly.
Installing a battery does not automatically mean a building will continue operating during a power cut.
We need to consider the site’s electrical distribution, maximum demand, battery inverter power, starting currents, changeover arrangements, earthing and, importantly, how long the customer needs those critical systems to remain operational.
So the conversation isn’t simply:
“How many kWh of batteries do you want?”
It’s:
“What happens to your business when the grid goes off, what absolutely has to stay running, and for how long?”
That’s a much better starting point.
When batteries don’t stack up
This is probably the most important part.
We don’t believe in recommending a battery simply because somebody is installing solar.
If a building already consumes virtually all its solar generation, has a relatively flat electricity tariff, limited peak-demand costs and no requirement for backup or resilience, the financial case for a battery may be weak.
And that’s fine.
We’ve advised customers not to install batteries where the numbers don’t justify them.
Equally, we sometimes see batteries sized against annual electricity consumption alone. That doesn’t tell us enough.
For larger projects, we want the site’s half-hourly electricity data. That allows us to see what is happening throughout the day and across different seasons.
We can then model different battery capacities and power ratings against solar production, tariffs and the site’s electrical demand.
Sometimes the answer is a smaller battery cycling regularly.
Sometimes it’s a multi-megawatt-hour BESS designed around the site’s overall energy strategy.
And sometimes the answer is no battery at all.
Commercial batteries in the UK are changing quickly
The technology available for commercial batteries UK businesses can choose from has developed rapidly.
We’re seeing increasingly sophisticated energy management systems and much better integration between solar PV, battery storage, EV charging, CHP and building loads.
That also means energy storage units installation needs to be treated as an electrical engineering project rather than simply another product attached to a solar system.
We need to consider the incoming supply, DNO requirements, maximum demand, electrical protection, fire safety, location, access, monitoring, backup arrangements and future expansion.
On larger sites, there may also be opportunities to generate additional revenue from the battery through aggregation or other energy-market services.
Those potential revenues need to be treated carefully. We would rather demonstrate that the core energy-saving case works and then show additional revenue separately than use optimistic assumptions to make a project look better than it really is.
Financing commercial battery storage
The falling cost of batteries has improved project economics, but capital cost can still be substantial on larger commercial systems.
There are now various solar battery storage finance options available for commercial and industrial projects.
Depending on the project, these can include conventional asset finance and leasing structures. Our recent feasibility work also considered off-balance-sheet leasing as a potential funding route for a larger commercial battery project.
For some organisations, buying the system outright will provide the strongest long-term return. For others, financing for solar battery storage may allow a project to start generating savings without tying up a large amount of capital.
But finance doesn’t turn a poor energy project into a good one.
The underlying savings still need to stack up.
Our approach to commercial battery storage
For us, commercial battery storage has to solve a real problem or create a measurable benefit.
That might mean storing surplus solar, buying electricity when it’s cheaper, avoiding higher-cost transmission periods, reducing peak demand, supporting EV charging, protecting critical systems during a power cut or potentially creating additional revenue from energy markets.
Often, the strongest projects combine several of those benefits.
As a commercial solar battery storage installer, our starting point is therefore not the battery. It’s the building.
Wherever possible, we work from half-hourly consumption data, electricity tariffs and solar generation modelling. We can then model different battery sizes and operating strategies to understand how the system would actually perform.
That gives facilities and finance managers something far more useful than a headline battery capacity and an estimated saving.
It tells them what the battery is expected to do, where the savings come from, how it will interact with solar and the grid, and what the realistic financial case looks like.
And if the figures show that the battery doesn’t stack up, we’ll say so.
After nearly 15 years designing and installing renewable energy systems, we’d rather design the right energy solution than sell a customer equipment they don’t need. If you’d like us to model your site, get in touch.
