How can the cheapest turbine quotation become the more expensive project?

The short answer

The lowest equipment price can lead to a higher project total when essential items are excluded, installation is harder or less of the generation can be used. Compare the same completed installation before ranking suppliers by price. A quotation for a turbine assembly and an offer for a broader electrical package are different purchases, even when both show the same rated kW.

Put both offers on one budget boundary

Start with the equipment and work needed to reach the same operating state. That might include the turbine, tower, foundation, controller, converter, local electrical work, delivery and commissioning. An item excluded by one supplier is not automatically unnecessary; its cost and responsibility may sit elsewhere in the project. Conversely, avoid adding an item twice when it is already included within another quoted package.

An example using budget units

This example uses invented budget units, not turbine prices. Offer A costs 100 units and excludes items estimated at 40. Offer B costs 120 units and excludes items estimated at 10. Their comparable totals are 140 and 130, respectively. A remains the lower equipment price, while B has the lower estimated completed-project cost. The conclusion changes if either allowance changes.

Illustrative comparison	A	B
Quoted package	100	120
Missing scope allowance	40	10
Comparable total	140	130

Keep uncertainty visible

Mark firm quotations, provisional allowances and unresolved exclusions separately. Freight and local works should have a stated basis rather than disappearing into a contingency percentage. Compare lifecycle spending and useful energy after the installation boundary is consistent. A nominally cheaper system is not economically better if the energy estimate, maintenance scope or load match is weaker. None of these comparisons establishes a MARSTON project price.

Test whether the ranking is robust

Try a simple sensitivity check before treating the budget ranking as settled. In the invented example, if A’s missing scope falls from 40 to 20 units, its total becomes 120 and the ranking reverses. That is a reason to obtain a firmer estimate for the uncertain scope, rather than arguing only about the original equipment discount. Keep the calculation attached to the assumptions it uses.