The profound flaws with Payback

Posted by on Mar 17, 2019 in Uncategorized | 0 comments

Simple payback, often referred to just as payback, describes the length of time needed for the savings generated by a resource efficiency project to return the initial investment made. It is calculated using the formula:

Thus, an investment of US$1,000 that yields regular annual savings of US$500 has a payback of two years. The annualized saving could be determined by a number of uneven cash flows, e.g. US$250 in year 1 and US$750 in year 2; here, the payback period is determined by adding up successive savings in the cash flow until they match the investment. If we are interested in the payback in months, then we would multiply the annual payback by 12.

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Fear of flying*

Posted by on Mar 14, 2019 in Uncategorized | 0 comments

I am writing this post from Goa, on the West coast of India. I flew here from Manchester, in the premium economy section of a Tui Boeing 787 Dreamliner. 

According to the ICAO carbon calculator [1] the aircraft will have burned 54 tonnes of fuel on each leg of the journey, which equates to 654kg of CO2 per passenger (2x the standard economy emissions due to the “premium” cabin seating). The plane was full, so I think the calculations are reasonable and, while I could argue that “premium economy” is not really twice the space or mass of standard economy, I don’t quibble with the figures. 

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