A 50 ton double girder crane at heavy duty burns more in electricity over ten years than the crane costs to buy. Here is where that power goes, what the motors draw from 5 to 100 tons, and which fixes actually pay for themselves.
Across 5 to 100 tons, a double girder crane carries 12 to 130 kW of installed motor power and costs roughly USD 1,020 to USD 29,820 a year to run at A5 to A7 duty. Over ten years at 20 tons and above, the power bill passes the purchase price of the crane. The hoist holds 65 to 80 percent of that consumption, and the auxiliary hoist wastes more than most buyers expect.
Double girder cranes get compared on capacity, span and price. Almost nobody puts an electricity number in the comparison sheet, because nobody has one at the enquiry stage. Then the crane runs for five years, someone reads the sub-meter on that bay, and the question changes from "what did it cost" to "why is it costing this much".
That gap is what this guide tries to close. Where the power actually goes on a double girder machine, what the motors draw from 5 to 100 tons, the part-load problem that comes free with a second hoist, how to work out your own cost per operating hour, what regenerative drives really recover, and which of the usual fixes pays back inside the service life. Some of the tables come from published studies and vendor cost sheets and we name the source. The rest are our own planning figures, and we label them rather than dressing them up as statistics.
It depends almost entirely on how far the crane travels, and that is why two published studies of the same machine class disagree so sharply.
The first is the simulation and measurement work published in Energies 2024, volume 17, issue 5, article 985. For a ship-to-shore or RTG style container crane it puts the hoist at about 62 percent of total energy, gantry travel at 31 percent and the trolley at 7 percent. Energy recovery is even more lopsided: about 81.5 percent of the recoverable energy sits in the hoist motion and only 3.7 percent in gantry travel. The same paper then models a land intermodal terminal and gets the opposite answer, with the gantry at 85 percent, the hoist at 9 percent and the trolley at 4 percent, because in a rail yard the crane runs along the track for most of the shift and barely changes height. Average hourly consumption at a marine terminal came out near 69.8 kWh against 17.23 kWh at the land terminal. Same crane class, four times the energy.
Vendor data tells a similar story. Risingcrane, writing in August 2026, puts the hoist at 55 to 75 percent of crane electricity.
A double girder crane inside a factory bay sits somewhere in the middle of all that, because a factory bay is short. Thirty to a hundred metres of runway travel per shift, twelve to thirty metres of trolley travel per cycle, and a lot of vertical work. Our planning split for that duty looks like this:
| Motion | Marine terminal (Energies 2024) | Land terminal (same study) | Factory double girder (SIEC planning figure) |
|---|---|---|---|
| Hoist, main and auxiliary | About 62% | About 9% | 65-80% |
| Long travel, bridge on the runway | About 31% | About 85% | 12-25% |
| Trolley along the bridge | About 7% | About 4% | 5-12% |
| Load pick and drop, losses, other | Included above | About 2% | Included above |
| Share of that motion's draw recoverable on lowering or braking | Hoist 81.5%, travel 3.7% | Not reported | Hoist 60-80% of lowering energy |
There is one more thing that separates a double girder crane from a single girder of the same capacity, and it is weight. A 20 ton, 22.5 m single girder bridge weighs roughly 7 to 9 tons. The double girder bridge for the same capacity and span weighs roughly 14 to 18 tons, and it carries a heavier crab with two hoists instead of one compact hoist. Every metre of long travel has to move that extra mass.
That does not make the double girder a bad buy. It makes it a different machine. You accept the extra dead weight to get more hook height, more duty class and a second hoist, and then you manage the energy deliberately instead of discovering it on the meter.
Installed power climbs faster than capacity does, because span and duty class both push the motors up. Published ranges for double girder machines put the 16 to 50 ton band at 30 to 80 kW total, with the lifting motor at 15 to 45 kW and the travel and trolley motors at 2.2 to 7.5 kW each. Above 100 tons the total routinely passes 100 kW and often reaches 150 kW, with main hoist motors from 45 to 55 kW and upwards.
Our planning table for standard factory duty, with a main hoist, an auxiliary hoist, a trolley and two long travel motors:
| Capacity | Main hoist | Auxiliary hoist | Trolley | Long travel (two motors) | Installed total |
|---|---|---|---|---|---|
| 5 t | 7.5 kW | - | 1.5 kW | 2 x 1.5 kW | 12.0 kW |
| 10 t | 13 kW | 3.0 kW | 2.2 kW | 2 x 2.2 kW | 22.6 kW |
| 20 t | 22 kW | 5.5 kW | 3.0 kW | 2 x 3.0 kW | 36.5 kW |
| 32 t | 30 kW | 7.5 kW | 4.0 kW | 2 x 4.0 kW | 49.5 kW |
| 50 t | 45 kW | 11 kW | 5.5 kW | 2 x 5.5 kW | 72.5 kW |
| 100 t | 75 kW | 22 kW | 11 kW | 2 x 11 kW | 130 kW |
Two warnings about reading that table.
First, the installed total is not the demand on your supply. The motions rarely run together, so feeders and busbars are sized on a simultaneity factor of roughly 0.6 to 0.8 of installed output. Second, and more important for the electricity bill, the number that matters is average demand across an operating hour, which is a different calculation entirely and usually lands between 45 and 65 percent of installed output.
Duty class inflates the motor size before you ever get to the energy question. Published guidance puts a 10 ton crane at A5 duty on 11 to 13 kW of total power, and the same 10 ton crane at A6 duty on 16 to 18 kW. You are buying the bigger motor whether or not you ever lift at rated capacity, because the duty class is about heat and starts per hour, not about maximum load.
Almost every double girder crane above 10 tons ships with two hoists. A heavy main hoist running slow, and a lighter auxiliary hoist running fast for the everyday lifts. The argument for the aux hoist is cycle time, and that argument is sound.
The energy argument is where it gets thin.
Induction motors are efficient at their nominal point and progressively less efficient away from it. The minimum efficiencies in EU Regulation 2019/1781 make the pattern plain: a 4-pole IE3 motor is rated 89.6 percent at 5.5 kW, 93.0 percent at 22 kW, 94.2 percent at 45 kW and 95.0 percent at 75 kW. Those are nameplate figures at full load. Move off full load and they fall.
Typical part-load behaviour for the two motor sizes that show up most often on a double girder crane:
| Load as a share of rated motor output | 5.5 kW motor, typical auxiliary hoist | 22 kW motor, typical main hoist |
|---|---|---|
| 100% | 89.6% | 93.0% |
| 75% | 88.9% | 92.4% |
| 50% | 86.8% | 90.6% |
| 25% | 81.5% | 85.4% |
Nominal points are the regulation's own 50 Hz, 4-pole IE3 figures; the part-load derates are our planning estimates and you should treat them as indicative rather than exact.
So consider an 11 kW auxiliary hoist on a 50 ton crane in a bay where most lifts are under 3 tons. That motor spends its life between 10 and 27 percent of rated output. Its efficiency has dropped eight to ten points below nameplate, and every kWh it draws produces more heat and less lift. On a single stroke this is a rounding error. Over 75,000 strokes a year it is not.
What to do about it, practically:
Size the auxiliary hoist from the median lift, not from half the main hoist. If your lift log says 80 percent of picks are under 5 tons, an 11 ton aux is reasonable. If the bay mostly handles 1 to 3 tons, an 11 ton aux is a motor running forever at a quarter load. A second, smaller hoist or a single-hoist configuration may be the better answer.
Consider a permanent-magnet motor for the auxiliary position. PM motors hold efficiency considerably better at part load than a standard induction motor, at a 20 to 35 percent premium on the motor price. On a motor that spends its life at 20 percent load, that premium is often the best value item on the electrical bill of materials.
And do not expect the motor regulation to fix this for you. As section 10 explains, crane hoist and travel motors are mostly brake motors, and brake motors are exempt from the IE4 stage. The law leaves them at IE3, so the part-load problem stays yours to solve.
Four steps. You can run the whole thing on a phone.
Step 1. Add up installed motor output. Use the table in section 2, or read the nameplates. If the crane was specified at A6 or above, the motors are already oversized for average work, which is exactly why you cannot simply multiply nameplate power by hours.
Step 2. Apply an average demand factor. This is the average share of installed output actually drawn across a working hour. Our planning factors are 0.45 for A5 moderate duty, 0.55 for A6 heavy duty and 0.65 for A7 severe duty. If you have a hoist counter and a load cell, measure it instead. The factor is the single number that moves the answer most.
Step 3. Divide by drivetrain efficiency. Use 0.85 for a VFD-driven crane, covering motor, gearbox and inverter losses together. Use 0.80 for an older slip-ring set with resistor control, where the resistor bank is burning rotor energy as its normal way of working.
Step 4. Multiply by your tariff and your hours.
A 20 ton double girder crane at A6 duty, worked through:
36.5 kW installed. Multiply by the 0.55 A6 demand factor and you get 20.1 kW of average output. Divide by 0.85 and the input is 23.6 kW. At USD 0.10 per kWh that is USD 2.36 for every operating hour. Run it 2,000 hours a year and the crane costs USD 4,720 in electricity.
Worth cross-checking against published figures rather than trusting the model. Risingcrane puts a 50 ton overhead crane at A5 duty between 80,000 and 150,000 kWh a year. The same method gives 50 tons at A6 an answer near 93,800 kWh, inside that band. A separate vendor analysis from June 2026 puts an electric overhead crane at 30 to 80 kWh per operating hour, against 8 to 15 litres of diesel per hour for a comparable diesel machine. At EUR 0.18 per kWh that is EUR 10,800 to EUR 28,800 a year for the electric crane, against EUR 27,200 to EUR 51,000 for the diesel one at EUR 1.70 per litre.
Same four steps, run across the range. Annual consumption and cost at a USD 0.10 per kWh tariff:
| Capacity | Installed power | Duty class | Operating hours a year | Annual kWh | Annual cost |
|---|---|---|---|---|---|
| 5 t | 12.0 kW | A5 | 1,600 | 10,200 | USD 1,020 |
| 10 t | 22.6 kW | A5 | 1,800 | 21,540 | USD 2,150 |
| 20 t | 36.5 kW | A6 | 2,000 | 47,240 | USD 4,720 |
| 32 t | 49.5 kW | A6 | 2,000 | 64,060 | USD 6,410 |
| 50 t | 72.5 kW | A6 | 2,000 | 93,820 | USD 9,380 |
| 100 t | 130 kW | A7 | 3,000 | 298,240 | USD 29,820 |
Read the last two columns against each other and one thing stands out. Going from 5 tons to 100 tons multiplies the bill by about 29. But hold the crane fixed and change only the duty class, and the bill still moves by a factor of nearly three:
| Duty class, same 50 t crane | Operating hours a year | Demand factor | Annual kWh | Annual cost at USD 0.10 |
|---|---|---|---|---|
| A5 moderate, one or two shifts | 1,600 | 0.45 | 61,410 | USD 6,140 |
| A6 heavy, two or three shifts | 2,000 | 0.55 | 93,820 | USD 9,380 |
| A7 severe, near continuous | 3,000 | 0.65 | 166,320 | USD 16,630 |
So when someone asks whether a 50 ton crane is expensive to run, the honest answer is that the tonnage is not the main variable. The duty class is. Two 50 ton cranes in the same plant, one on A5 and one on A7, differ by USD 10,490 a year in electricity with identical nameplate capacity.
Buyers compare a crane price against a crane price. The power line only becomes visible once the machine is installed, and by then the decision is years old. Here is that line, against the purchase price band for each capacity, and against a mid-range maintenance budget so the two operating costs sit side by side.
| Capacity | Annual power cost | Ten-year power cost at 3% a year | Typical FOB crane price | Power as a share of purchase price |
|---|---|---|---|---|
| 5 t | USD 1,020 | USD 11,700 | USD 12,000-18,000 | 65-97% |
| 10 t | USD 2,150 | USD 24,650 | USD 18,000-28,000 | 88-137% |
| 20 t | USD 4,720 | USD 54,100 | USD 32,000-48,000 | 113-169% |
| 32 t | USD 6,410 | USD 73,500 | USD 55,000-80,000 | 92-134% |
| 50 t | USD 9,380 | USD 107,500 | USD 85,000-130,000 | 83-126% |
| 100 t | USD 29,820 | USD 341,900 | USD 180,000-320,000 | 107-190% |
At 20 tons and above, ten years of electricity exceeds the price of the crane itself at the cheaper end of the price band. That is at a USD 0.10 per kWh tariff. It is not a universal statement.
Run the same 20 ton crane in Germany, where Eurostat band IB industrial rates including taxes and grid fees sat near EUR 0.27 per kWh in the first half of 2026. Annual electricity becomes about EUR 12,750, ten years about EUR 146,200, against a purchase price around EUR 29,000 to EUR 44,000. The power bill is then three to five times the crane price. In China at the equivalent of USD 0.082 per kWh the ratio shrinks to roughly 90 to 135 percent. Same machine, same duty, radically different economics depending on where it is plugged in.
This is why an energy conversation belongs in the quotation stage and not in the fifth year of ownership. If you want the rest of the ownership cost on the same basis, our double girder cost and TCO guide covers purchase, installation and maintenance with the same method.
Yes, and it happens every time the crane lowers a load. A loaded hoist lowering is a motor driven backwards by gravity, which makes it a generator. On a full-load lowering stroke, 60 to 80 percent of the rated hoist power is available as electrical energy.
Whether you get any of it depends entirely on the drive. A conventional VFD has a diode rectifier that cannot push power back into the supply, so a chopper dumps it into a braking resistor: 5 to 15 kW per braking event on a small hoist, resistor surface temperatures of 200 to 300 degrees Celsius, extra cooling load in the switch room, and a recovery rate of exactly zero. Risingcrane puts that waste at CNY 8,000 to CNY 15,000 a year, roughly USD 1,100 to USD 2,100, on a crane with frequent start-stop duty.
Now run the numbers on a 50 ton double girder crane at A6 duty.
A full rated load of 50 tons lowering 10 m releases 50,000 x 9.81 x 10 = 4.905 million joules, or 1.36 kWh. But a heavy duty crane rarely lifts at rated capacity. The CMAA service classification for Class D describes loads approaching 50 percent of rated capacity handled constantly. Take that 50 percent as the average, and a typical stroke is 25,000 x 9.81 x 10 = 2.45 million joules, or 0.68 kWh of potential energy.
At the measured 30 to 40 percent recovery rate, the average lowering stroke nets about 0.24 kWh back onto the DC bus. Multiply by 300 cycles a day over 250 working days, and that is 75,000 cycles a year and roughly 17,900 kWh recovered from the main hoist alone. At USD 0.10 per kWh, USD 1,790 a year.
The auxiliary hoist adds more than you would guess, because it runs more often. Lighter loads, so less energy per stroke, but on many cycles. Around 0.06 kWh per stroke over the same 75,000 strokes is 4,500 kWh, or USD 450. That only works if the aux hoist drive shares the DC bus or has its own feedback path. On plenty of cranes, the aux hoist still has a plain braking resistor and recovers nothing.
Long travel and trolley braking add a small amount. The published figure for recoverable travel energy is only about 3.7 percent of travel consumption, and travel is 12 to 25 percent of the bill on a factory crane. On a 50 ton machine that is roughly USD 150 to USD 250 a year.
Total realistic recovery on a 50 ton A6 double girder crane: around USD 2,400 a year. That lands inside the USD 1,800 to USD 3,200 range published for an A5 hoist-only retrofit, which is a useful independent check on the method.
One thing worth understanding: recovery scales with cycles, not with tonnage. A 10 ton crane doing 500 cycles a day recovers more energy in a year than a 50 ton crane doing 40.
Depends on the cycles, not on the capacity. Published vendor cost tables for A6 to A8 duty, assuming 200 to 500 cycles a day, a blended USD 0.10 per kWh and 2,000 operating hours a year:
| Configuration | Capital cost | Annual energy saving | Payback |
|---|---|---|---|
| Dynamic brake VFD, the baseline | USD 8,000-15,000 | None | - |
| Regenerative VFD, DC bus plus one regen unit on a three-motion crane | USD 14,000-25,000 | USD 2,500-6,500 | 2.5-4.5 years |
| Active front end drive per crane | USD 18,000-32,000 | USD 3,500-8,500 | 2.0-4.0 years |
| Active front end plus active power factor correction | USD 22,000-40,000 | USD 4,000-10,500 | 2.5-4.0 years |
| Shared DC bus plus one active front end, four-crane bay | USD 45,000-75,000 | USD 12,000-28,000 | 2.0-3.5 years |
Those are the generous numbers, and they assume heavy duty. Drop to A3 to A5 duty with fewer cycles and the same hardware pays back in four to six years. A published A5 case at 80 to 120 cycles a day puts a hoist-only regenerative retrofit at USD 9,000 to USD 14,000 against USD 1,800 to USD 3,200 of annual saving, which is 3.5 to 6 years. Full three-motion regeneration at A5 costs USD 18,000 to USD 28,000 against USD 2,500 to USD 4,500, giving 4.5 to 7 years.
Three rules of thumb that hold up across the published cases:
Under about 100 cycles a day, retrofit the hoist and leave the bridge and trolley on resistors. The hoist holds most of the recoverable energy and the travel motions will not earn their hardware.
At 16 tons and above with frequent start-stop duty, a line feedback unit is the standard answer. The same source reports that steel and foundry projects select it in roughly 90 percent of cases, which is a strong signal about what actually lasts in that environment.
And always check whether a demand charge applies before trusting the payback. Where the utility charges more than USD 10 per kVAr per month, the low end of every payback range above becomes the realistic one.
This is where the double girder crane has an advantage over a single girder machine, because heavy bays usually hold several cranes.
| Site shape | Topology | Why |
|---|---|---|
| One or two cranes, hoist drive 50 kW or more | Active front end or line feedback unit per crane | Simplest route to grid feedback, and current THD under 5 percent with power factor 0.99 comes with it |
| Three or more cranes in one bay, four or more preferred | Shared DC bus, optionally one feedback unit | One crane's lowering energy is consumed by another crane's lifting. Rectifier hardware falls 50 to 70 percent, supply capacity 20 to 30 percent |
| Frequent start-stop, or a weak grid connection point | Supercapacitor bank or hybrid | Roughly 1,000,000 charge cycles against about 3,000 for lithium cells. Absorbs transients without exporting to the grid |
| Legacy slip-ring or DC crane with no DC bus | Hoist drive replacement first | Largest saving per dollar on any single change, see below |
| Mixed bays with different duty | Hybrid: active front end plus shared bus plus storage | Highest combined saving, cost is project specific |
Reference costs from the same source: an active front end rectifier runs CNY 8,000 to CNY 25,000 per drive and cuts 15 to 20 percent of drive energy on units at 50 kW and above, with a payback of 7 to 12 months. A shared DC bus set is CNY 15,000 to CNY 40,000 and pays back in 12 to 18 months. A supercapacitor bank is CNY 6,000 to CNY 20,000 per set, saves 10 to 25 percent, and pays back in 18 to 36 months.
Now the part that applies to a large share of the installed double girder fleet in steel mills and heavy fabrication shops. Those cranes are still on wound-rotor, or slip-ring, motors with resistor control. That is how they get variable speed: rotor energy is dumped as heat in a resistor bank as the normal mode of operation. The efficiency penalty is structural rather than incidental, and no amount of maintenance will remove it.
The retrofit market has been building kits rather than full modernizations, and the arithmetic is straightforward. Konecranes describes a retrofit as 70 to 95 percent standardized, needing 5 to 30 percent of the engineering work of a one-off modernization, which is why a fleet-wide programme can be quoted once and applied many times. Where the motor itself has to change, custom-built motors with the electrical data of a smaller frame but the mounting dimensions of the old one avoid rebuilding the machinery house, cutting a motor swap from about a week to about one day.
EU Regulation 2019/1781 sets mandatory motor efficiency classes, and the way it is written leaves most crane motors at IE3 whether the buyer wants IE4 or not.
From 1 July 2021, three-phase motors from 0.75 kW to 1,000 kW, with 2, 4, 6 or 8 poles, must reach at least IE3. Motors from 0.12 kW to 0.75 kW must reach IE2. From 1 July 2023, three-phase motors from 75 kW to 200 kW with 2, 4 or 6 poles must reach IE4, but that stage explicitly excludes brake motors, Ex eb increased safety motors and other explosion-protected motors. Ex eb and single-phase motors from 0.12 kW sit at IE2.
The exemption that matters is in Annex I. Motors with an integrated brake that forms part of the inner motor construction and cannot be removed or separately powered during efficiency testing are out of scope for the requirements. Multi-speed motors are exempt. Totally enclosed non-ventilated motors are exempt. Motors fully integrated into a product whose performance cannot be tested independently are exempt.
That covers most crane hoist and travel motors. The practical map looks like this:
| Motor position on a double girder crane | Typical rating | What the regulation requires |
|---|---|---|
| Main hoist, brake motor | 7.5-75 kW | IE3 minimum. The IE4 stage does not reach it, because the integrated brake exemption applies |
| Auxiliary hoist, brake motor | 3-22 kW | IE3 minimum. Same exemption |
| Trolley travel, brake motor | 1.5-11 kW | IE3 minimum |
| Long travel on a very large outdoor machine, non-braked | 75-200 kW | IE4 required since 1 July 2023, because it is not a brake motor |
| Explosion-protected or cleanroom duty motor | 5-30 kW | IE3 where applicable, IE2 for Ex eb increased safety motors |
| Pole-changing multi-speed motor | Any | Exempt, under Annex I point 2(n) |
For reference, here is what moving from IE3 to IE4 actually buys you at 50 Hz and 4 poles:
| Rated output, 4-pole | IE3 nominal efficiency | IE4 nominal efficiency | Points gained |
|---|---|---|---|
| 5.5 kW | 89.6% | 91.9% | 2.3 |
| 11 kW | 91.4% | 93.3% | 1.9 |
| 22 kW | 93.0% | 94.5% | 1.5 |
| 37 kW | 93.9% | 95.0% | 1.1 |
| 55 kW | 94.6% | 95.4% | 0.8 |
| 75 kW | 95.0% | 95.6% | 0.6 |
The gains are real but small, and they shrink as the motor gets bigger. On the 22 kW motor in the table, 1.5 points of efficiency is around 440 kWh a year on a crane running 2,000 hours at 55 percent average load. At USD 0.10 per kWh that is about USD 44. Buy IE4 where the law requires it, or where the motor is cooking itself and you want it to run cooler. Do not buy it expecting the bill to move.
Short answer: neither, in any way that shows up on the energy line. Both supplies deliver the same kWh for the same work. The differences that matter are about tolerances, motor sizing conventions and procurement, and one of them affects how long the motor lasts.
NEMA rates motors at 460 V on a nominal 480 V, 60 Hz system, with a voltage tolerance of plus or minus 10 percent and a frequency tolerance of plus or minus 5 percent. IEC rates motors at 400 V or 690 V on a 50 Hz system and splits tolerance into two zones: zone A allows plus or minus 5 percent voltage with 2 percent frequency variation, zone B allows plus or minus 10 percent voltage with plus 3 percent and minus 5 percent on frequency.
The interesting difference is the service factor. NEMA MG 1 lets a motor be run continuously above its nameplate rating by the service factor. A 400 hp motor with a 1.15 service factor can be run continuously at 460 hp. IEC does not recognise the service factor at all. It requires the purchaser to specify a duty type from S1 to S10 instead, and the honest description of a crane motion is S4, intermittent periodic duty with starting, or S5, the same with electric braking.
On a crane, the NEMA convention is a trap. Running a motor into its service factor means it runs hotter, and hotter means shorter insulation life and shorter bearing life. On a machine that starts and stops hundreds of times a day, that is exactly the wrong bargain. Specify the duty and buy a motor that is properly sized for it.
There is one genuine energy effect, and it is small. For the same power, a higher voltage means lower current, and lower current means smaller cable losses. On a 100 m runway at 130 kW installed, the difference between 400 V and 480 V amounts to at most a few hundred kWh a year. Real, but never the reason to choose a supply. Where a crane crosses a 50 Hz and 60 Hz boundary, the bigger issue is not energy at all: a fixed-speed 50 Hz motor on a 60 Hz supply runs 20 percent faster, which changes lift and travel speeds. On a VFD crane the drive sets the frequency and this disappears entirely.
EN 15011:2014 and IEC 60204-32 are the standards to check against before specifying a drive or motor change on either supply.
Most factories pay for two things, not one. Energy in kWh, and demand in kW or kVA at the monthly peak. Add a power factor penalty on top and a crane with no correction becomes more expensive than its kWh suggests.
There are two common penalty structures. One bills demand as actual kW multiplied by 0.95 and divided by the plant power factor, so anything below 0.95 or 0.90 lagging pays a premium. The other charges directly for reactive demand in kVAr.
A crane without correction runs at roughly 0.80 to 0.85 lagging. Multi-pulse diode converters hold above 0.95 across most of their envelope but drop below it at low load and low speed, and a crane spends a lot of its time at low load and low speed.
The arithmetic, on a 50 ton double girder crane drawing 50 kW of average demand at 0.80 power factor, on a tariff with a USD 12 per kW monthly demand charge:
| Plant power factor | Apparent power for 50 kW | Billed demand | Penalty against the 0.95 threshold | Annual penalty per crane |
|---|---|---|---|---|
| 0.95, the threshold | 52.6 kVA | 50.0 kW | - | - |
| 0.90 | 55.6 kVA | 52.8 kW | 2.8 kW | USD 400 |
| 0.85 | 58.8 kVA | 55.9 kW | 5.9 kW | USD 850 |
| 0.80 | 62.5 kVA | 59.4 kW | 9.4 kW | USD 1,350 |
| 0.70 | 71.4 kVA | 67.9 kW | 17.9 kW | USD 2,570 |
Ten cranes in a bay at 0.80 power factor is USD 13,530 a year in penalties alone, for a problem a capacitor bank costing a few thousand solves. There is also a physical cost beyond the tariff: at 0.70 power factor you need 71.4 kVA of transformer and cable capacity to deliver 50 kW of real work. Upgrading the supply to carry reactive current you are not using is capital spent on nothing.
The alternative to capacitors is an active front end drive, which delivers power factor near 0.99 and current distortion under 5 percent as a by-product of the drive you were buying anyway. Where a crane is already due for a drive replacement, that is usually the cheaper route to the same result.
Every number above is a tariff multiplier. Here is what the same kWh costs in the markets we quote into most often.
| Market | Industrial rate | Source and period |
|---|---|---|
| China | USD 0.082 per kWh, about CNY 0.571 | BusinessEurope 2024 industrial comparison; Intratec, January 2026 |
| European Union average | EUR 0.199 per kWh | BusinessEurope, 2024 industrial prices |
| United States average | 9.17 US cents per kWh | US EIA Electric Power Monthly, June 2026 |
| California | 20.74 US cents per kWh | US EIA, June 2026 |
| Germany | EUR 0.27 per kWh | Eurostat band IB via euenergy, first half 2026, taxes and grid fees included |
| Belgium | EUR 0.25 per kWh | Eurostat band IB, first half 2026 |
| Italy and Ireland | EUR 0.24 per kWh | Eurostat band IB, first half 2026 |
| Netherlands | EUR 0.22 per kWh | Eurostat band IB, first half 2026 |
| Austria | EUR 0.20 per kWh | Eurostat band IB, first half 2026 |
| France | EUR 0.18 per kWh | Eurostat band IB, first half 2026 |
| Portugal and Spain | EUR 0.17 and EUR 0.16 per kWh | Eurostat band IB, first half 2026 |
Two caveats before you use that table. The European figures include taxes and grid fees, while the energy-only component runs EUR 0.09 to EUR 0.14. Use the all-in number for an energy calculation, because that is what actually leaves the bank account. And the US figure is the national average of what utilities billed industrial customers in June 2026, which hides a lot: California paid 20.74 cents against 9.17 cents nationally.
The spread is the point. The same regenerative drive that pays back in four years in Texas pays back in about fifteen months in Bavaria, on identical hardware, because the tariff is three times higher.
Ordered by payback. Do the cheap ones first, and note that the last row is on the list to make a different point.
| Priority | Measure | Cost | Energy effect | Payback |
|---|---|---|---|---|
| 1 | Right-size the auxiliary hoist to the load range it actually serves | USD 3,000-8,000 | 3-7% of crane consumption | 2-4 years |
| 2 | Replace the main hoist braking resistor with a line feedback unit | USD 9,000-14,000 | 15-25% of hoist energy | 1.5-3 years |
| 3 | Correct power factor, by capacitor bank or by choosing an active front end drive | USD 6,000-12,000 | Avoids USD 400-2,570 per crane a year where a penalty applies | Under 12 months |
| 4 | Convert slip-ring hoist motor and resistor control to squirrel cage with VFD | USD 15,000-35,000 per crane | 20-35% of crane consumption | 3-6 years |
| 5 | Shared DC bus across three or more cranes in one bay | USD 15,000-40,000 per set | Rectifier hardware down 50-70%, supply capacity down 20-30% | 12-18 months |
| 6 | Add an active front end rectifier to one large crane | USD 8,000-25,000 per drive | 15-20%, plus distortion and power factor benefits | 7-12 months |
| 7 | Go beyond IE3 to IE4 where the regulation does not require it | 20-35% premium on the motor | Under 1% | Does not pay on its own |
That last row is deliberate. Row 1 costs less than a tenth of row 4 and pays back faster, because it is a sizing decision rather than a hardware purchase. The habit of reaching for the biggest efficiency class is understandable and often misplaced. Match the motor to the load it actually sees, and get a regenerative path onto the hoist, before spending anything on motor class.
Meter the feedback path, not just the crane feed. A bidirectional class 0.5S meter to IEC 62053-22 on the regenerated circuit separates "we recovered energy" from "we happened to run fewer cycles this month". Without that distinction, every saving claim becomes an argument.
Trend it monthly and alarm on a deviation of more than 15 percent from the baseline. A failing converter or a change in working pattern shows up there weeks before it shows up in an annual report. That alarm is the difference between measuring a retrofit and hoping about one.
Baseline before you change anything: 30 days of kWh per shift, cycle count from the hoist counter, and average load per cycle from the load cell or from the drive's torque estimate. Then the payback is a measurement rather than a projection, and the case for the next crane writes itself.
Everything above is one of two things, and the article says which as it goes. Where a figure comes from a published study or a vendor cost sheet, we name the source. The rest are our own planning figures, produced from the method in section 4, and they should be treated as inputs to a conversation rather than as measured results.
Our own figures in this article: the factory duty motion split, the installed power table, the part-load efficiency derates, the annual consumption and cost model, the ten-year comparison, the regeneration worked example, the power factor table and the retrofit priority order.
The published anchors: Energies 2024, volume 17, issue 5, article 985, for the motion split and the recovery shares. Risingcrane, August 2026 and July 2026, for the regenerative drive options, cost ranges, payback figures and the 50 ton annual consumption band. Yuantai, July 2025, for installed power ranges by capacity and duty. EU Regulation 2019/1781 for the motor efficiency classes and the exemption wording. NEMA's motor standards comparison for the NEMA and IEC differences. The US EIA Electric Power Monthly for June 2026 for US rates. Eurostat consumption band IB via euenergy for European rates in the first half of 2026. BusinessEurope for the 2024 EU, China and US industrial price comparison. The CMAA service classifications for the load factor assumption. Konecranes and Port Technology for the retrofit standardization figures.
The shared assumptions: 0.85 drivetrain efficiency for VFD-driven motions, 0.80 for resistor-controlled slip-ring sets. Electricity price escalation of 3 percent a year over ten years, which gives a ten-year multiplier of about 11.46 on the first year's bill. Average demand factors of 0.45 at A5, 0.55 at A6 and 0.65 at A7.
One caveat matters more than the others. The motion split is the most sensitive assumption in the whole calculation, and it changes with the shape of the bay. A crane running 80 m of runway per cycle will have a very different split from one running 8 m. If you replace a single number in this article with your own measurement, replace that one.
For capacities from 5 to 100 tons, our planning model gives roughly 10,200 to 298,000 kWh a year, which is USD 1,020 to USD 29,820 at a USD 0.10 per kWh tariff. A 50 ton crane at A6 duty sits near 93,800 kWh and USD 9,380 a year. Published figures for a 50 ton machine at A5 duty run from 80,000 to 150,000 kWh, which brackets our number, so the method is at least in the right place.
The hoist, by a distance. In a factory bay the hoist takes 65 to 80 percent of consumption, long travel 12 to 25 percent and the trolley 5 to 12 percent. Published studies of intermodal cranes put the hoist between 55 and 75 percent, with one land terminal model flipping the result entirely because its cranes travel kilometres along the track each shift. If your bridge travels more than about 30 m per cycle, expect the travel share to climb.
For cycle time, usually yes. For energy, only if it is sized to the load range it actually serves. An 11 ton auxiliary hoist on a crane whose lifts average 1.5 tons runs at about 14 percent of rated output, where motor efficiency is eight to ten points below nameplate. Size that hoist from the median lift rather than from half the main hoist, and consider a permanent-magnet motor for that position, because PM motors hold efficiency far better at part load and the auxiliary hoist is where part load lives.
Yes, whenever it lowers a load. A loaded hoist drive becomes a generator at 60 to 80 percent of rated hoist power. On our 50 ton A6 model the main hoist alone recovers about 17,900 kWh a year, worth roughly USD 1,790 at USD 0.10 per kWh, and the whole crane recovers around USD 2,400. That requires a regenerative drive or an active front end. A standard drive with a braking resistor recovers nothing and turns the energy into 200 to 300 degree resistor heat instead. Our 5 to 100 ton double girder crane range is available in either configuration, and we will size the regenerative pair against your cycle log.
On published vendor figures for A6 to A8 duty, a regenerative VFD pays back in 2.5 to 4.5 years, an active front end drive in 2.0 to 4.0 years, and a shared DC bus across four cranes in 2.0 to 3.5 years, all against a blended USD 0.10 per kWh and 2,000 operating hours. At A5 with fewer cycles the same hardware takes 4 to 6 years, and an A5 hoist-only retrofit 3.5 to 6 years. Where the utility charges more than USD 10 per kVAr per month in demand charges, use the low end of each range.
Yes, and the reason is dead weight. A 20 ton, 22.5 m single girder bridge weighs roughly 7 to 9 tons, while the double girder bridge for the same capacity and span weighs roughly 14 to 18 tons and carries a heavier crab with two hoists. Every long travel stroke moves that extra mass. The gap per cycle is modest, since long travel is only 12 to 25 percent of consumption in a factory bay, but over 2,000 hours a year it is a real line item. Buyers accept it to get more hook height, more duty class and a second hoist, and then manage the energy deliberately.
If you want the energy line modelled against your own tariff, duty class and cycle count, send us the lift data and we will run it before you commit to a motor, a drive or a retrofit programme. The three things that decide most of the bill are the duty class, the auxiliary hoist sizing and whether the hoist has a path for the energy it makes on the way down. Get those right at the quotation stage and the ten-year number looks very different from the one on the meter today.
Our double girder crane range from 5 to 100 tons is quoted with regenerative drive options, and we will size the electrical package to your supply voltage and tariff. If you want the maintenance side of the same calculation, the double girder crane maintenance and overhaul guide covers the interval schedule and the cost of deferred work.
Related articles:
Crane Energy Consumption: What a Single Girder Crane Really Costs to Run
Double Girder Crane Cost & Total Cost of Ownership Guide: 10 to 100 Ton Price, Installation, Maintenance & 10-Year TCO (2026)
Double Girder Crane Maintenance and Overhaul Guide 2026: Schedules, Duty Classes and 10-Year Cost
Double Girder Crane Installation Guide 2026: 8-Stage Process, ISO 12488-1 Tolerances, Load Test & Cost
Crane Modernization vs Replacement: What the 2026 Numbers Say About Refurbishing Existing Cranes