Very little reference has been made in this guide to the
important aspects of if and when it is worth making an
investment in a more energy-efficient technology. The great
differences between countries and regions in the prices of
engines, fuel and skilled labour make it meaningless to present
quantitative financial guidelines. However, the following basic
calculation should assist a vessel operator in investment
decisions. It should be noted that the method is a quick
approximation; if a large investment is being considered, a more
detailed financial analysis is necessary. Total cash expenditure
should be calculated by summing the purchase price, installation
cost, any net lost earnings plus the additional annual
maintenance cost incurred by the new investment. The net lost
earnings should be estimated from the number of days the vessel
will be out of service multiplied by the owner's normal net
earnings (after the deduction of costs and crew share) from the
vessel per day. The money to be invested could hav