Introduction
Lifts rarely appear in a building’s energy strategy, and when they do the discussion usually stops at the motor. That is the wrong place to start. Vertical transportation is a small share of a building’s total consumption, but it is a share almost entirely decided at specification — and the useful question is not whether a lift can be made more efficient, but where its energy actually goes. That answer differs completely between a busy office tower and a six-storey residential block.
Where the energy actually goes
A lift spends electricity in three distinct states. Running energy is what everyone pictures: the car moving with a load. Idle is the car stationary with the doors closed while the controller, lighting and ventilation are still awake. Standby is what remains once the installation has powered down everything it can.
The proportions are not what intuition suggests. Measured across real installations, the standby share ranges from roughly a tenth of annual consumption to very nearly all of it, with the highest shares in buildings where the car is rarely called. In a residential building the car can be stationary for more than ninety per cent of the year. There, a more efficient machine saves almost nothing, because almost nothing is being spent on travel in the first place.
This single fact decides which measures are worth paying for. It also explains why two lifts with identical hardware produce very different annual figures: usage, travel height and rated speed move the number more than the drive technology does.
ISO 25745: the standard that makes the claim checkable
ISO 25745 is the series that turns “energy-efficient” from a sales adjective into a figure that can be compared. Part 1 specifies how to measure the actual energy consumption of an installed unit and how to repeat that check later to verify nothing has drifted. Part 2 covers energy calculation and classification for lifts. Part 3 does the same for escalators and moving walks.
Part 2 is the one quoted in tenders. It applies to traction, hydraulic and positive drive lifts with a rated speed above 0,15 m/s, on a single unit basis, and it assigns an energy class from A to G, A being the best. The class is never meaningful on its own: it is assigned together with a usage category, and the standard defines six of them by daily trips, from very low at 50 trips a day to extremely high at 2,500. The same lift can be class A in one category and several classes worse in another. A class quoted without its usage category tells you nothing.
It is worth knowing what the measurement leaves out. For lifts, Part 1 does not count shaft lighting, heating and cooling inside the car, or machine room lighting. A figure produced under the standard and a figure read off the building’s sub-meter are therefore not the same number, and a specification that treats them as interchangeable will not reconcile later.
Before ISO 25745: VDI 4707
The A-to-G label for lifts did not begin with ISO. The German guideline VDI 4707 Part 1 introduced it first and was widely used across Europe before the ISO series matured; ISO 25745-2 has since taken over that role internationally. Older product literature and older building documentation may still quote a VDI class. The two scales are not interchangeable, so a class carried across from one scheme to the other has to be re-established, not re-labelled.
What actually moves the number
Standby management is the first lever in any building with moderate or low traffic. Powering down car lighting, ventilation, displays and parts of the controller after a defined period of inactivity attacks the largest part of the bill precisely where travel is rarest. ISO 25745 measures standby power after five minutes of inactivity, which is a reasonable proxy for how the installation behaves overnight.
Regenerative drives work from the opposite end. They return the energy released when the car is overhauled by its load — a full car descending, an empty car rising — to the building’s supply instead of burning it as heat in a resistor. The saving scales with how often that happens, so regeneration pays in the high usage categories and pays very slowly in a quiet residential block. Recommending it everywhere is how a genuine technology acquires an undeserved reputation.
The machine and drive sit in between. A gearless permanent-magnet machine with a variable-voltage, variable-frequency drive removes gearbox losses and the starting currents of older arrangements, and correct counterweight balancing keeps the machine working near its efficient region instead of fighting the load in both directions. At European level, Regulation (EU) 2019/1781 sets ecodesign requirements and IE efficiency classes for electric motors and variable speed drives; whether a particular lift machine falls within its scope depends on the exclusions written into that regulation, and the supplier’s declaration of conformity is what settles it for a given machine.
LED car and shaft lighting remains the cheapest measure on the list, and in a low-traffic installation it is also among the most effective, because car lighting runs during idle as well as during travel.
Hydraulic and traction are not interchangeable here
A hydraulic lift draws its energy on the up-trip and descends under gravity, which looks attractive until the peak current and the absence of any regeneration are counted. For low rise and low traffic — a two or three stop installation with modest use — it remains a defensible choice, and the energy difference is smaller than the headline suggests precisely because standby dominates. For a busy building with meaningful travel height, traction with a regenerative drive is a different class of answer.
Modernisation is where the savings are largest
The highest-yield energy work on a lift is almost never a new lift. Replacing a 1990s drive and controller with a modern VVVF drive, a genuine standby mode and LED lighting, while retaining the guide rails, car frame, doors and the shaft itself, changes the annual figure substantially at a fraction of the cost and disruption of a replacement. It also allows the result to be measured against the prior installation under Part 1 — which is the only way to prove the saving rather than assert it.
Where the figure gets used
Energy performance stops being an internal matter the moment the building seeks certification. Neither LEED nor BREEAM has a credit written specifically for lifts, so the equipment’s contribution appears in the energy model, in the metering strategy and in the product documentation — and an ISO 25745 figure with its usage category is exactly what the energy modeller needs as input. In the European regulatory frame, the Energy Performance of Buildings Directive drives whole-building performance; its definition of a technical building system centres on heating, cooling, ventilation, domestic hot water, built-in lighting and building automation, with lifts treated as a further building service that can be brought into the building’s energy calculation. In practice the lift figure is asked for, and a building whose supplier cannot produce one is at a disadvantage.
How Bronze Lift approaches it
We size an installation against the building’s real traffic rather than a standard assumption, because the usage category decides which measures earn their cost. We state energy figures together with the basis they were produced on, and we say so plainly when a measure — regeneration most often — will not pay in a given building. For modernisation we quantify the before and after on the same basis, so the saving is something the building owner can check rather than take on trust.
Conclusion
Energy-saving lifts are a real engineering result rather than a slogan, but only when the claim is attached to a standard, a usage category and a measurement. Decide where the energy goes before deciding what to buy: in a quiet building, standby and lighting; in a busy one, the machine, the drive and regeneration. ISO 25745 exists so that the answer can be written down, compared between suppliers, and verified again later.