Energy waste in a commercial building rarely announces itself. Nothing is broken. The lights come on, the heating works, the compressor runs, the bill arrives and gets paid. The waste is in what runs when it doesn’t need to, what runs harder than it needs to, and what runs against something else.
With wholesale gas above 200p a therm this month, its highest level since December 2022, and winter contracts priced well above where they were in the summer, the cost of that waste has gone up sharply. The good news is that most of it is visible, if you know what to look for. Almost every sign below can be found in data you already have: half-hourly electricity data from your supplier, gas reads, and the bills themselves.
Here are the twelve we see most often, roughly in the order we would check them.
- A high overnight baseload
This is the single most useful number in your data. Take a weekday, look at consumption between 2am and 4am, and ask what is still running. In a well-managed office, overnight load might be 15–25% of the daytime peak. In many buildings it is 40–60%.
A high baseload is rarely one thing. It is a combination of plant left on, IT and vending equipment, lighting on timers that nobody reviewed, and small loads across many circuits. But it is the cheapest waste to remove, because everything running at 3am is by definition running for nobody.
- Weekends that look like weekdays
Compare a Sunday’s profile with a Tuesday’s. If the shape is similar and the total is more than about half, the building’s schedules are not following its occupancy. Heating, ventilation and lighting are the usual suspects, and the fix is usually in the BMS calendar.
- Heating and cooling running at the same time
This is the shoulder-season problem, and September is when it starts. When the outside temperature drops, as it did to 13–15°C this week, the heating switches on, but the cooling setpoints have not moved since summer. If heating is set to 21°C and cooling to 22°C, the two systems fight each other all day.
In the data, it shows up as gas consumption starting while electricity baseload stays high or rises. The fix is a wider deadband: heat to 20°C, cool at 24°C. Nobody notices the difference in comfort. The plant does.
- Plant that starts before anyone arrives
Look at when the morning ramp begins. If consumption climbs from 4am and staff arrive at 8am, the building is being conditioned for four empty hours. Older controls default to long pre-heat periods because they were set conservatively once and never revisited. Optimum-start functions, which calculate the start time from the outside temperature, are available on most modern BMS systems and are frequently switched off.
- Compressed air that never stops
In manufacturing, compressed air is often the most expensive utility on site and the least measured. If your compressor runs at the weekend when no production is scheduled, it is feeding leaks. A typical industrial site loses 20–30% of its compressed air through leaks, and the compressor consumption on a non-production day tells you almost exactly how much.
- Lighting on 24/7
Walk past your site at 11pm. If the car park, warehouse or office is lit, check whether it needs to be. Lighting is a small load per fitting and a large load in total, and it is one of the few kinds of waste you can see from the road. In the data, it is part of the overnight baseload; on site, it is usually a timer or a PIR sensor that has been overridden.
- Estimated bills
An estimated bill is not just an accounting nuisance. It means nobody, you or your supplier, knows what the site actually used, and any analysis built on it is guesswork. If more than an occasional bill is marked estimated, the meter is either not being read or not communicating. Get it fixed before doing anything else, because every other sign on this list depends on real data.
- A capacity charge for capacity you don’t use
Half-hourly electricity supplies carry an agreed capacity (kVA) charge, paid monthly whether you use it or not. Businesses that have downsized, moved processes, or installed more efficient equipment often continue paying for capacity agreed years ago. Compare your agreed kVA with your actual maximum demand over the last 12 months. If actual demand is consistently below 70–80% of agreed capacity, you can usually reduce the agreed figure, but be careful, because exceeding it carries penalty charges.
- Poor power factor
If your bills include a reactive power charge, your site’s power factor is below the threshold (typically 0.95). Motors, older lighting and some IT loads are the usual cause. Power factor correction equipment is a well-understood, relatively low-cost fix, and the reactive charge on the bill tells you exactly what it is worth.
- Gas at 3am
Gas consumption overnight in a building that is unoccupied means heating or hot water is running for nobody. In offices, it is usually the boiler schedule or a hot water system that maintains temperature 24 hours a day. In hospitality, it is often kitchen equipment left on standby. Half-hourly gas data is less common than electricity, but daily reads are usually enough to see the pattern.
- Consumption that doesn’t follow the weather
Heating consumption should rise and fall with the outside temperature. Plot monthly gas against heating degree days for the last two years. If the relationship is weak or if a mild month uses as much as a cold one, the heating is being driven by something other than demand: schedules, faulty controls, or a system running at full output regardless of conditions. If the relationship has shifted upward year on year, something has deteriorated.
- Nobody can explain last month’s bill
This is the sign that underlies all the others. If the person responsible for energy cannot say, within a few minutes, why this month’s consumption was higher or lower than last month’s, the building is being paid for rather than managed. That is not a criticism of the person. It is almost always a data problem: the information exists, but it is scattered across supplier portals, PDFs and spreadsheets, and pulling it together takes longer than anyone has.
What each sign is typically worth
The numbers vary enormously by building, but as a rough guide from the sites we work with:
| Sign | Typical saving when fixed |
| Overnight baseload reduction | 5–15% of electricity |
| Weekend scheduling | 3–8% of total |
| Heating/cooling deadband | 3–6% of heating and cooling |
| Optimum start | 2–5% of heating |
| Compressed air leaks | 20–30% of compressor energy |
| Capacity charge correction | £1,000–£10,000 a year per site |
| Power factor correction | Reactive charge eliminated, typically £500–£5,000 a year |
Individually, none of these is dramatic. Together, on a multi-site estate, they routinely add up to 10–20% of the energy bill, without a capital project.
How to start
Pick one site. Pull 12 months of half-hourly electricity data from your supplier (you are entitled to it) and any gas reads you have. Work through signs 1 to 4. They take about an hour and need no equipment.
If you want to go further than the first four signs, our practical guide to reducing business energy costs covers the fixes in more detail.
Then the harder question: how do you keep watching, every month, across every site, without it becoming somebody’s full-time job?
How Enerlytic helps
Enerlytic collects half-hourly electricity, gas and water data automatically from every site and meter, and flags the patterns above: a baseload that has crept up, a weekend that looks like a weekday, gas at 3am, without anyone having to open a spreadsheet. It turns an annual audit into a continuous one, and gives you the evidence to show your finance director where the savings came from.
Want to know which of these twelve signs are showing up in your buildings? Our Energy Diagnostic works through your data and tells you. Book a free 30-minute demo at www.enerlytic.co.uk.
