How Prosperity Powered Two Tower Cranes From a Limited Grid Supply

Smithfield Square is a 305-apartment development in Birmingham's Digbeth district. With two WOLFF 630B tower cranes required on a long-running programme, Prosperity Developments needed a temporary-power strategy that could meet demanding crane peaks without bringing the cost, emissions and operational burden of a conventional diesel arrangement onto site.

The solution was an Enertainer supplied by WOLFF Onsite. Connected to a limited three-phase low-voltage grid supply, the battery energy storage system charges steadily and releases high power when the cranes demand it. Between January and May 2026, the arrangement imported 32,793.35 kWh of electricity and supported the site's lifting operations while delivering an estimated £39,192 cost saving and avoiding 62.6 tonnes of CO₂e against the modelled diesel alternative.

A Power Challenge Shaped by Location and Demand

Smithfield Square sits within Birmingham's Clean Air Zone and close to residential properties. Prosperity therefore had strong reasons to reduce local emissions and noise, while working within restricted construction hours. The site also needed continuous provision for two aircraft warning lights, adding a small but important out-of-hours load.

Tower cranes present a particular temporary-power challenge. Their average energy use can be relatively modest, but starting motors and making demanding lifts can create short, substantial peaks. A power system sized only around average consumption may be unable to respond, while sizing conventional generators around the maximum theoretical peak can leave large engines running inefficiently at low loads for much of the day.

Leon Bradshaw, Project Director at Prosperity Developments, explained that diesel generation was considered but not pursued. Previous experience with Stage V generators, fuel deliveries, supporting peak-power equipment and planned maintenance had introduced complexity and periods of downtime. Fluctuating diesel prices also made long-term operating costs harder to predict.

“Since we deployed the Enertainer unit, we haven’t had any downtime. It has been very reliable and it has saved us a considerable amount of cost.”

— Leon Bradshaw, Project Director, Prosperity Developments

Using the Grid Differently

Rather than viewing the available grid connection as too small for two large tower cranes, it was used as a steady source of energy for the Enertainer. The connection trickle-charges the battery over time. When a crane calls for more power than the grid can provide, the Enertainer responds from stored energy, supplying the peak without interrupting operation.

This distinction between energy and power is central to the business case. A site may have enough grid energy available across the day but insufficient instantaneous capacity for crane starts and lifting peaks. Battery storage closes that gap. It allows the site to make productive use of a constrained connection rather than defaulting to diesel purely because of momentary peak demand.

At Smithfield Square, one Enertainer supports both WOLFF 630B cranes. The integrated arrangement also benefits from remote monitoring. WOLFF Onsite can view the unit's status through its telematics and alert the site team if attention is needed. Leon described an instance where a minor CPU reset was identified remotely and resolved with a quick call, without affecting crane operation.

What the Diesel Alternative Would Have Required

For a like-for-like comparison, WOLFF Onsite modelled a conventional temporary-power arrangement capable of supporting the same crane operations and aircraft warning lights. It comprised two 250 kVA Stage V generators, two Peak Power 200 Flybrid units, two battery packs for the warning lights and two 2,000-litre fuel bowsers.

The Flybrid units are important to the comparison. Each would operate as a peak shaver, supporting its generator during sudden spikes in crane demand. This would allow a smaller generator to serve the crane than a set sized entirely around the brief maximum peak. Although more efficient than simply oversizing the generators, the arrangement still adds equipment, hire cost, interfaces and maintenance requirements.

The model assumed the two generators each consumed 13 litres of diesel per hour at 25% load and operated for 50 hours per week. Across the 20-week comparison period, that equates to approximately 26,000 litres of diesel. At £1.46 per litre, fuel alone came to £37,960. Equipment hire for the generators, Flybrid units, warning-light battery packs and bowsers added £50,400, producing a total diesel-alternative cost of £88,360. AdBlue was not included, making the estimate a conservative representation of the diesel option.

A £39,192 Saving Over Five Months

The Enertainer comparison combines actual imported energy, available client electricity tariffs and actual equipment hire charges. Electricity cost £12,168 across the period, while Enertainer hire totalled £37,000. The combined cost was therefore £49,168—£39,192 less than the modelled diesel arrangement.

That is a 44% reduction in total temporary-power cost over the analysis period. The saving does not come from electricity being compared with diesel in isolation. It reflects the wider system: hiring one battery energy storage unit using an available grid connection versus multiple generators, peak-shaving units, battery packs and fuel bowsers, together with the fuel needed to operate them.

Battery storage can also reduce exposure to some of diesel's less visible costs. Fewer fuel deliveries mean less administration, fewer vehicle movements and less time spent monitoring fuel levels. Removing continuously running engines reduces routine checks and servicing demands. Improved price visibility can support budgeting because electricity and fixed hire charges are less exposed to the same day-to-day fuel-price volatility. The precise saving will always depend on the site's loads, tariffs, programme and available connection, but Smithfield Square demonstrates why the whole power architecture, not just the price of one unit of energy, must be compared.

Cutting CO₂e by 91%

The carbon difference was even greater. Using an emissions factor of 2.65 kg CO₂e per litre, the modelled 26,000 litres of diesel would have produced 68.9 tonnes of CO₂e. The Enertainer's 32,793.35 kWh of imported grid electricity produced approximately 6.3 tonnes using the stated grid factor of 0.193 kg CO₂e per kWh.

The resulting saving was 62.6 tonnes of CO₂e, a reduction of approximately 91%. Because the Enertainer is powered from the grid, it eliminates combustion at the point of use. Alongside the greenhouse-gas reduction, this removes generator exhaust emissions from the immediate work area and supports a quieter site. For a project close to homes and operating within a major city's clean-air agenda, those local benefits are significant even though they are not assigned a monetary value in the comparison.

“Typically, we would have generators set up and running throughout construction hours. Because the Enertainer is battery-powered and connected directly to the grid, there is no additional noise pollution.”

Reliable Power With Savings Still to Come

For Prosperity, performance on site has been as important as the calculated savings. In an application where power interruptions affect crane productivity and the wider construction programme, a lower-carbon solution must also be dependable. Leon described the Enertainer as almost 100% reliable during its first seven months on site and praised the continued monitoring and telephone support provided by WOLFF Onsite.

The January-to-May results cover only the first five months of measured performance. Prosperity expects the arrangement to remain in operation for a total of 12 to 18 months, creating the potential for further cost and carbon savings as the development progresses. Final outcomes will depend on future energy use, tariffs and programme duration, but the evidence to date establishes a strong direction of travel.

Smithfield Square shows that a constrained grid connection does not automatically rule out electric power for large lifting equipment. By separating steady energy supply from instantaneous crane demand, the Enertainer enables the grid to work harder, removes the need for a complex diesel-led arrangement and gives the project a quieter, more predictable power solution.

“We expect to have this setup operating for 12 to 18 months, so there will be considerable savings across the whole project.”

— Leon Bradshaw, Project Director, Prosperity Developments

Methodology note: The diesel alternative is a representative model based on manufacturer fuel-consumption data, estimated operating hours, a diesel price of £1.46/litre and WOLFF Onsite hire rates. Enertainer figures use monitored site energy, available client tariffs and actual hire charges. January-March electricity costs use the April tariff because historic tariff data was unavailable; May energy use includes an estimate for a temporary monitoring-data gap.