# Capital expenditure constraints 

Because TIMES optimises the entire energy sector, results can sometimes show sudden, large shifts in technology stocks if a newly available technology is clearly more economically efficient than existing stocks. LED lighting is a great example: TIMES will often choose to invest heavily in replacing all current lighting technologies with LEDs, since the efficiency gain is ideal for the overall system. In reality, this sort of one-off investment is not always realistic. For some selected technologies, we limit the available expenditure to keep growth rates at reasonable levels, no matter the other system context. 

The selected technologies, and their relevant uptake limits, are listed in {numref}`tab_cap_limits`. Note that technology uptake may be limited by a percentage annual growth rate, or by additional annual capacity. It is also possible to combine these limits, in which case the overall limit is the sum of the additional capacity and the percentage increase in any given year. 

Note that these rates are by assumption only, and have only been applied when unrealistic uptake rates were identified. Unusual capacity limits in this table can sometimes signal that the underlying technology context could benefit from more sophisticated modelling detail. 


```{csv-table} Capital expenditure limits for selected technologies
:header-rows: 1
:name: tab_cap_limits
:file: tables/capacity_limits_uc.csv
```