Commercial Estimators

Anyone have a simple method for estimating power cost for a tower crane?

Like how to get to Kwh useage per month based on ????

Our method is very simple and basic. We have only had about three experiences with tower cranes. All in an urban environment.

The extent of our electrical costs were, the dedicated 100 amp service and the use charges which were less than $100 per month.

When compared to the cost of the rental and set up of a 11 story tower crane which for us ran over $400,000 for a year and a half time frame.

Added to that was the cost of an operating engineer on off hours when the wind exceeded 30 miles per hour. The tower crane needs to swivel freely at that wind speed and regulations require it to be occupied. So in the scheme of things our electric costs for the crane were so slight to the overall costs that to spend a significant amount of time determining horsepower and kwh usage and cost seemed counter productive. That may not be the case in others experiences, as I said we have only had three instances of using and setting up a tower crane.

Austin "Bud" Mayberry

I bid a public works project last year and a tower crane would have been a perfect fit due to the tight quarters and power lines along the only accessable locations for truck cranes.  It could have been installed in a stairwell that could have been finished after the crane was removed. 

 There were several trades that could have used the crane and paid for it to the CM from their crane budgets built in to their bids.  The CM and architect didn't want to  address the issue, so each trade was required to figure out their own means.  Subcontractors were preparing bids to submit to all the GC bidders equally and couldn't develop a separate bid for one that was going to offer a tower crane.

It was only 2 stories, but once the steel and precast floor planks were set on the second floor, a crane couldn't pull into the building for the roof steel and a much larger crane was necessary to reach the far end of the building over high power lines along the street.  The exterior walls were masonry, so stair stepping the structure to back a truck crane out, avoiding the power lines until the last setup wasn't practical.

My question is, on projects with tower cranes, who pays for it and how is that cost distributed to the contractors using it?

Either the Construction Manager or the General Contractor has paid for it in our experiences. We have bid on projects where the Construction Manager provided the tower crane and the sub contractors paid for the operator and the time of use when each one was using the tower crane.

We have also worked on a project were the Construction Manager provided and paid for the tower crane and it's use during normal working hours and we only had to schedule its use between contractors.

We have also provided a tower crane and a personell lift on several projects were we carried the cost of the tower crane and lift and managed the use of both with no charge to the subcontractors.

The working theory behind our arrangement is no different than when the general contractor provides staging scaffolding. If it makes economical sense then it should be done. The cost of a tower crane however, is such that it is very seldom viable. But when it is almost nothing else will accomplish the work. Ninety nine times out a hundred, we find that any other method that can be made to work will be more ecomonical. The test is exactly as you suggested. Each subcontractor can work up his cost for how to get his work in place on his own and give a deduct for a crane provided for his use. Then it is a simple matter of showing the owner which is the most cost effective for price and schedule.  We have even had a project cancelled and redesigned because the cost of accessing the site with a tower crane was so exhorbitant. I understand that in European countries they are much more prevelant even for smaller projects. They must have a different cost associated with them than I have found. Some people like to see them proposed because they look so impressive but few understand the costs involved and are willing to use alternative methods when they find out and when it is possible.

bubmay is correct.  Go to Europe and they use cranes for everything.  Generally the general contractor is responsible for providing the crane(s) and personnel hoists.  Having all trades figure their own lifting is inefficient or will just not work.  On two jobs we subcontracted the erection of a large scaffolding/work platform to access a high ceiling area (one for a church and one for a performing arts theater), allowed access and use by all the trades but told them up front not to include these costs.  So theoritically the savings were reflected in their bids.  Even if this method didn't save money, it was quicker and safer than multiple lifts, platforms, etc.  With respect to tower cranes, generally they require 480 volt power plus a foundation so when you figure shipment to the site, erection, foundation, operator(s), rental costs, disassembly and removal of the foundation, the power usage costs are almost nothing.  If the CM is doing his job, he should provide the tower cranes and personnel hoists for the whole project.  But in any case, tower cranes are expensive compared to other hoisting means but sometimes they are the only solution