Building Energy Management Systems: Reduce Energy Consumption and Improve Your EPC

Mark Wakeford is Chairman of EvoEnergy, Strategy Director of the Global Solar Council, Chair of the West Midlands Solar Taskforce and host of The Building Podcast. This article draws on his conversation with Ron Purcell, Vice President of the Building Controls Industry Association (BCIA) and a Product Manager at Siemens with over 40 years in the HVAC sector.

 

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I’ve spent a long career putting buildings up, and there’s a particular feeling I’ve come to recognise. You hand over a beautifully designed, genuinely efficient building, and then you walk away wondering whether the controls will ever be used the way they were meant to be. Whether the one person you trained will still be there in eighteen months. Whether the whole thing will quietly get switched to manual override.

 

So I was pleased to sit down for the Building Podcast with Ron Purcell, Product Manager at Siemens, Vice President of the Building Controls Industry Association (BCIA), and someone who has spent more than forty years in heating, ventilation and air conditioning. Ron makes a case I think our industry has been too slow to hear: that energy management systems are the fastest, cheapest carbon and cost reduction available to most commercial buildings, and we keep cutting them out of the budget anyway.

 

Here’s what came out of that conversation.

 

 

Key takeaways

• A building energy management system (BEMS) coordinates heating, cooling, ventilation, shading and metering so that building services work together rather than against each other.
• Moving a building from standard controls to advanced controls can cut energy use by up to 30% in an office environment, according to BCIA figures.
• Typical payback on a controls upgrade is three to four years, against ten to fifteen years for fabric upgrades or plant replacement.
• Only around 20% of UK buildings have any form of BEMS in place.
• Controls are currently not well recognised in EPC methodology, which is one of the BCIA’s central asks of government.
• Controls are usually the last package appointed on a project, and therefore the first thing value engineered out.

 

 

What is a building energy management system?

 

A building energy management system, or BEMS, is the control layer that coordinates all of a building’s energy-using services from a single point, heating, cooling, ventilation, lighting, shading, metering and increasingly on-site generation and storage.

 

Ron’s analogy was the best I’ve heard: it’s the conductor of the orchestra. Left uncoordinated, your services will happily fight each other, heating running against cooling, plant firing up at eight o’clock in the morning because the timeclock says so rather than because anyone’s in the building. A BEMS makes those decisions in the round.

 

That coordination goes further than most people expect. If the system knows the blinds are dropping to shade a west elevation, it also knows it can back the heating off in that zone. If a building has a gas boiler, a heat pump and some heat recovery, it can decide which of them to lean on at any given hour based on what costs least and emits least. And through sub-metering, it can show you exactly where your energy is going, which parts of the building are underperforming, and by how much.

 

One detail worth noting: the acronym has changed. It used to be BMS, for building management systems. The E for energy was added deliberately, and that tells you everything about how the discipline’s priorities have shifted

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Why energy management systems moved from the plant room to the boardroom?

 

Twenty years ago, as Ron put it, a control system was a necessary evil. It was a line item you paid for when the building was built and then didn’t think about it again. Three things changed that.

 

Carbon became a board-level issue. Under SECR, large organisations have to report their energy and carbon. Green credentials now matter commercially. The energy manager who had no voice at board level suddenly has one, because the numbers they produce end up in a published report.

 

Systems learned to talk to each other. Open communication protocols mean a controller from one manufacturer speaks the same language as a controller from another, and as your boilers, chillers and heat pumps. Coordinating a mixed estate is no longer the bespoke integration nightmare it once was.

 

Sensors got cheap. Wireless, battery-powered devices mean you’re no longer pulling copper across a building to add a sensor or a meter. That has collapsed both the hardware and the installation cost, and it means you can get genuine room-by-room granularity for a fraction of what it used to cost.

 

As Ron said: if you can’t see it, you can’t measure it, and you can’t control it.

 

 

 

The number that should get a finance director’s attention

 

The BCIA advocates for BS EN ISO 52120-1, the standard that classifies building automation and control systems into efficiency classes, A for the best, D for the worst, in much the same way you’d grade a fridge.

Most UK building stock, on Ron’s assessment, sits at Class C at best. Take an office building from Class C to Class A with advanced controls, and you can save up to 30% of your energy consumption. That’s across electricity and whatever else you’re burning.

 

Now put that next to the payback. Fabric upgrades, boiler replacements, heat pump installations, all of them matter, all of them are part of the net zero picture, and all of them tend to run to a ten to fifteen year return, with serious disruption to the occupants while the work happens.

 

A control upgrade from Class C to Class A? Three to four years. Minimal disruption. Possibly a few extra cables.

 

That’s not a marginal gain. That’s low-hanging fruit that’s been hanging there for two decades.

 

Energy management systems and your EPC

This is where it gets frustrating.

 

The Minimum Energy Efficiency Standards regime is tightening. In its June 2026 interim response, the government confirmed its intention that from 2031, privately rented non-domestic buildings over 1,000 square metres in England and Wales will need to reach EPC B, where cost effective. The previously proposed interim EPC C milestone for 2027 has been dropped, and the changes still require secondary legislation. But the direction of travel is not in doubt.

 

So landlords are going to be looking hard at how they lift a rating. And EPC methodology, as it stands, is built around insulation, fabric and heat source. All important. But it substantially misses the point that how you control those systems has an enormous effect on what the building actually consumes.

 

That’s the BCIA’s central ask of government, set out in the white paper they launched at the House of Lords last October. Three parts to it:

 

1. Recognise controls within the EPC framework. The measurement methodology exists — BS EN ISO 52120-1 is ready-made and could be adopted as a soft standard rather than hard legislation.
2. Bring back enhanced capital allowances for control technologies. It’s a targeted, proven tool, and it worked before.
3. Treat controls as part of the triangle, alongside building fabric and low-carbon heating technology, rather than as an afterthought.

 

I said in the conversation that enhanced capital allowances would be highly appropriate here, and I stand by that. It’s specific, it’s targeted, and it drives exactly the behaviour we need.

 

Only one in five buildings has one

 

Here’s the statistic that stopped me: BEMS of varying types and levels exist in only around 20% of UK buildings.

 

One in five. Which means there’s an 80% opportunity sitting there, and much of it in the existing stock that we know accounts for the overwhelming majority of buildings we’ll still be using in 2050.

 

Retrofit isn’t uniformly easy, and Ron was honest about that. A 1960s school with a single-pipe system and cast iron radiators is not a candidate for an all-singing, all-dancing system; there’s a law of diminishing returns and no point gold-plating controls for plant that can’t respond to them. But you can almost always do something. Control each radiator so you’re only heating the classrooms in use. Add metering so you can see where the waste is.

 

And critically, the cost profile has changed beyond recognition. The perception that a BEMS means a large panel on a wall, bespoke programming and a specialist consultant, and a six-figure invoice, is a twenty-year-old perception. A small doctors’ surgery or a retail unit can now be sensibly controlled at a cost that pays back in a few years. The perception is the barrier now, not the price.

 

It isn’t only about energy

 

The other thing that has shifted since COVID is that people don’t have to be in your building.

 

If you’re a landlord or an occupier, your building is now competing for its own occupants. It needs to be somewhere people actively want to be, comfortable, healthy, well-ventilated, and, to be blunt about it, somewhere people can be productive.

 

Energy management systems are central to that. CO2 sensing is a good example: CO2 builds up as people breathe, rooms feel stuffy, and there’s solid evidence that elevated levels degrade learning outcomes in schools.

 

Demand-controlled ventilation means you’re not running plants flat out from nine until three, you’re aspirating the space as the air quality actually degrades. You save energy and you get a better environment. Those two things are usually presented as a trade-off. Here they aren’t.

 

The catch, as Ron pointed out, is that a well-controlled building is invisible. Walk in, the temperature is right, the lighting is right, and you think nothing of it. If the controls industry does its job perfectly, nobody notices it exists. As a civil engineer whose best work has all been buried, I have some sympathy.

 

 

Stop value engineering the controls out

 

This was Ron’s call to arms for our industry, and it’s the part I’d most like our clients and our supply chain to hear.

 

Controls are typically the last package appointed on a project. By the time they’re being priced, the concrete has overrun, the fittings have been upgraded, and someone is looking for savings. So the controls get trimmed.

 

You spend £100 million on a building and then shave a relatively trivial sum off the system that determines how efficiently that building will run for the next thirty years.

 

It isn’t a criticism of anyone in particular, it’s just where the industry currently sits. But when the payback on proper controls is three to four years, it’s a saving that costs you money. And I’ll be honest: I see exactly the same thing happen to the solar array on the roof. We’re near the end of the programme too. Let’s do twenty panels instead of thirty.

 

This is an education problem. People generally aren’t aware of the consequences of the decisions they’re making at that moment. Our job, mine, the BCIA’s, the trade federations’, is to make them aware before the decision gets taken.

 

Where controls fit alongside generation and storage?

 

From where I sit, the picture is fairly simple. Solar PV generates. Battery storage shifts that generation to when you need it. EV charging turns it into fleet mileage. And energy management systems decide, hour by hour, what gets used, when, and from where, which is what turns a collection of technologies into a genuinely efficient building.

 

My product is solar, and I’ll happily admit it’s an easier sell: the win is visible and it’s quick. But I’m not convinced there’s anything like enough awareness of what changing the BEMS can do. There should be. The two work together, and the business case for doing both at once is stronger than for either alone.

 

The final word: this is not a technical problem

 

Ron’s closing point was the one I’ve heard in almost every sustainability conversation I’ve had on this podcast, and it bears repeating.

There is no missing technology. We already have everything we need to make buildings perform dramatically better than they currently do. What we’re short of is the will, sometimes the budget, and, most often, the knowledge in the hands of the people who make the decisions.

We have the answers. The task now is getting the right people to know that we have them.

 

Frequently asked questions

 

What does BEMS stand for?

BEMS stands for building energy management system. It was previously known as a BMS, or building management system; the “E” was added to reflect the system’s central role in managing energy consumption and carbon, rather than simply keeping a building running.

 

How much energy can a building energy management system save?

According to BCIA figures, upgrading from a standard Class C control system to an advanced Class A system under BS EN ISO 52120-1 can reduce energy consumption by up to 30% in an office building. Savings apply across electricity and other fuels, and depend on the building’s age, use pattern and existing plant.

 

What is the payback period on a controls upgrade?

Typically three to four years for a Class C to Class A upgrade. By comparison, fabric upgrades, boiler replacements and heat pump installations generally return over ten to fifteen years, and involve significantly more disruption to building occupants.

 

Will a BEMS improve my EPC rating?

Improved controls reduce actual energy consumption, but current EPC methodology is weighted heavily towards fabric, insulation and heat source, and does not fully credit the contribution of building controls. The BCIA is lobbying government to recognise controls within the EPC framework. In the meantime, a controls upgrade delivers real consumption and carbon savings that support wider compliance and reporting obligations such as SECR.

 

Can you retrofit an energy management system into an older building?

Yes, though the scope depends on the existing plant. Modern buildings are relatively straightforward. Older stock, a 1960s school with a single-pipe system, for example, may only support incremental measures such as individual radiator control and sub-metering, but these still deliver savings.

 

Wireless, battery-powered sensors have made retrofit far less invasive and far more affordable than it was.

 

Are energy management systems only worth it for large buildings?

No. That perception dates from an era when a BEMS meant a large control panel, bespoke programming and specialist commissioning. Standardised, pre-configured controllers and wireless devices now make control systems viable for small commercial premises, a doctors’ surgery, a retail unit, a restaurant, at costs that pay back within a few years.