One of the analyses that needs to be performed is a techno-economic analysis which would give a guideline on the feasible products in relation to the required operating parameters. Jouny et al. considered the end-of-life net present value (NPV) to be the criteria with which some of the most common CO

_{2}RR products are evaluated [

40], although other methods that directly compare the cost of product are used as well [

46,

47,

52]. The end-of-life NPV (in

$) can be defined as the summation of the initial investment (capital expenditure) and the present value of all future cash flows till the end-of-life of the plant. In short, the NPV takes into account the time value of money and indicates whether the studied project will be feasible over its lifetime. If NPV is negative, it means the present value of all future cash flows combined is less than the capital expenditure today, then it is not considered economically viable unless there are subsidies. The NPV can be calculated as:

where, CF

_{t} is the cash flow (

$) in the year t, i is the discount (interest) rate (%) and n is project lifetime (years) [

53,

54]. The estimation in such model is based on the material and energy balances for the process as well as estimated capital and operating expenditures. For a CO

_{2}RR plant, the capital expenditure constitutes mainly of the electrolyzer cost, the cost of product separation equipment, such as distillation columns and other supporting and auxiliary equipment (balance-of-plant). Whereas, the operating expenditure is mainly associated with the electricity cost, CO

_{2} acquisition cost and the cost of maintenance. The variance of the end-of-life NPV of CO

_{2}RR products between two scenarios is shown in

Figure 5. In the two distinct scenarios, namely, the base case and the optimistic case, the current density, cell voltage and conversion are changing variables. Whereas, the production rate (100 ton/day), lifetime of the plant (20 years), operating time (350 days/year), electricity price (0.03

$/kWh), CO

_{2} price (40

$/ton), interest rate (10%), product selectivity (90%) and electrolyzer cost (920

$/m

^{2}) remain constant [

40]. The values of variable parameters for the two cases are taken based on benchmarks currently feasible and future targets. The values of current density, cell voltage and conversion for base case are 150 mA/cm

^{2}, 2.3V, 30%, respectively, whereas for optimistic case the values are 300 mA/cm

^{2}, 2V, 50%, respectively. From this analysis, the more promising products are the carbon monoxide, formic acid and propanol, while ethanol and ethylene show feasibility under optimistic conditions.

Among the various operating parameters previously discussed as system metrics, sensitivity analysis on the different CO

_{2} reduction products shows that the selectivity and voltage are the most important electrolyzer parameters [

40]. For the selectivity or FE, to which the current requirement is inversely proportional, higher selectivity would mean lower energy spent on the by-product(s), including hydrogen formation, and product separation. This in-turn would reduce the operating costs greatly. Furthermore, as the current requirement decreases, to maintain the current density, the electrolyzer area required would also decrease, thus reducing the capital expenditure. For the cell voltage, it is directly related to the power requirement so lower cell voltage would plummet the required power and further reducing the operating cost. It should also be noted that current density, which remains critical to catalyst performance, can be the least significant electrolyzer parameter beyond a threshold because the electrolyzer capital cost and current density are considered to have an inverse square relationship [

40]. However, the significance of capital expenditure in comparison to operating expenditure diminishes linearly with time. As a result, it is necessary to achieve a particular threshold (200–400 mA/cm

^{2}) [

40]. Increasing the current density beyond the threshold would have very little impact on the NPV so it is advisable to focus on increasing selectivity or reducing cell voltage instead.