The report finds that bunker delivery notes and tank soundings have the lowest investment cost. However, unless tank sounding is automated, these systems have higher operational costs than fuel flow meters or direct emissions monitoring because manual readings have to be entered in monitoring systems.
Fuel flow meters have the highest potential accuracy. Depending on the technology selected, their accuracy can be an order of magnitude better than the other systems, which typically have errors of a few percent.
By providing real-time feed-back on fuel use or emissions, fuel flow meters and direct emissions monitoring provide ship operators with the means to train their crew to adopt fuel-efficient sailing methods and to optimise their maintenance and hull cleaning schedules.
Except for bunker delivery notes, all systems allow for both time-based and route-based (or otherwise geographically delineated) systems.