Installed Capacity vs CAPEX: Finding the Economic Sweet Spot

In utility-scale solar design, more installed capacity does not always translate into a better project. While increasing DC capacity can boost annual energy production, there comes a point where additional modules begin to deliver diminishing economic returns. Identifying this balance is a key aspect of modern PV system optimisation and can have a significant impact on overall project economics.

A useful way to assess this trade-off is by separating project costs into capacity-dependent and fixed costs. In many utility-scale PV projects, modules, mounting structures and DC cabling account for approximately 60% of total CAPEX. These costs scale directly with installed DC capacity, meaning every additional module increases project expenditure. By contrast, a large proportion of the remaining costs, including grid connection infrastructure, substations, development costs, land agreements and much of the AC electrical system, remain largely unchanged regardless of the installed DC capacity.

For sites with a fixed AC export limit, increasing the DC ratio can improve energy yield by allowing the plant to capture more energy during lower irradiance periods. However, as DC capacity continues to increase, inverter clipping and export constraints become increasingly significant. The result is that each additional megawatt of installed DC capacity contributes progressively less exportable energy, while still carrying the full cost of the associated modules, structures and cabling.

This is where advanced PV simulation and modelling become essential. By combining detailed energy yield analysis with CAPEX modelling, designers can accurately quantify the relationship between installed capacity, energy production and project cost. Rather than relying on rules of thumb, developers can identify the point at which additional investment no longer delivers proportionate returns.

Ultimately, effective solar design optimisation is not about maximising module count it is about maximising value. The most successful projects are those that achieve the lowest LCOE, ensuring that every pound invested in PV infrastructure generates meaningful energy production, revenue and long-term project performance.