ANSWER

A Life-Cycle Assessment (LCA) is a study/report that attempts to quantify the environmental impact of an object or process. This might be something like determining the carbon footprint of a car and depending on the scope, could include all the energy used to mine and transport the materials, assemble the car and deliver the car, operate it for its lifetime and then dispose of it.

LCA is a term associated with Sustainable Design. If you come across this on the exam you know you’re dealing with sustainability/environment issues.

You are probably more likely to come across Life Cycle Cost Analysis (LCCA) problems. Similar to an LCA, the LCCA is used to quantify the actual dollar amount of a process, object or building over the entire life of that thing. This is a Financial issue.

Some of the lifetime costs associated with a building are: design, construction, repairs & maintenace, utilities and maybe demolition one day. In its most simple form, your lifetime cost = Construction + (Operation Cost per year * Years)

Payback period is the amount of time it takes something to save or generate an amount of money equal to how much it costs. In our world this is often used to evaluate mechanical systems or maybe high efficiency windows...things that will save the building money on operating costs. If it costs $1000 to install a solar panel and that solar panel will save you $200 per year the payback period is 5 years. In those 5 years the solar panels saved you as much money as they cost to buy.

Is it better to have a higher initial price with lower operating costs or a lower initial price with higher operating costs?

Well that’s the question, isn’t it?! The answer is, it depends. No right or wrong, it's a case-by-case issue, but this is the classic ARE kind of comparison question. The point at which the lines cross is where the high initial cost system is now a lower overall cost. The big question is how much time that takes.

EXERCISE ANSWER

12,000 BTU = 1 Ton. This is one conversion you need to remember.

System A is more cost effective after 10 years. It is also more cost effective at 20 years, but only by about $7000.