Nate,
There is more to the equation then raw BTU's in/out. Those ratings are under a fabricated set of test conditions that should never exist in actual usage. They use a delta T thats to to large to exist in most applications, would cause internal condensation and destroy the unit. The efficiency of a standard <90% efficient unit is never whats stated. The unit is also unable to modulate so its going to short cycle and loose efficiency there.
A >90% efficiency unit will almost always have the ability to modulate. Allowing the unit to avoid short cycles and increasing seasonal efficiency.
You stated that you will save about $105 a year over a 20 year life span I see some units that are 40+ years old. That equates to a $2100 savings assuming that fuel prices never increase in that time period I am pretty sure thats the same or less then the price difference between the two units. I will make another stretch and say that fuel prices are going to increase in the next 20 years and the savings may be more then double or triple that. 20 years ago gas was about $0.36 per therm so thats 360 % increase.
I also believe in protecting the environment. You will save 81 Therms per year, Currently there are about 50 million houses that heat with natural gas. If half of those were to save the same 81 therms thats 2,025,000,000 therms of gas saved and not contributing to global warming. Many places mandate higher efficiency equipment, do a google search on the United Kingdoms policy.
I could also argue that if the only thing manufactured was high efficiency equipment that the prices would drop substantially. The environment aside, a good portion of our natural gas is imported I would not be a stretch to say that importing less gas from unstable regions would A) help the economy by sending less money over seas B) help with national security by making us more self reliant. Setting the environment, the economy and national security aside. Natural gas is a feed stock for some many other processes that we depend on it seems foolish to burn it. So many of our plastics, medicines, and chemicals depends on natural gas (and oil) for their production. No more plastics in 100 years because we burned all the feedstock for its production.
I installed a 98% efficient boiler and took an 84% combustion <50% seasonal efficient unit out of use. You said the 15% difference is not huge but I know I would sure like to pay 15% less or make 15% more. I think its a sizeable enough difference.
Pickups not hauling loads should not be allowed to drive because they get 17 MPG?
I wish I was able to get 17 mpg in my pick up truck, I average around 12 mpg even less when I am plowing thats why I only drive my truck when I absolutly have to.
Lou
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