Mitsubishi system.

[ishoot308]

Originally Posted by ITD

So the calculation is not that easy and I'm a little skeptical of the numbers in ishoot's link. Electric rates have skyrocketed this year, especially in Mass. due directly to Gov. Patrick's clean air initiative and the resultant closing of coal plants. Add to that a shortage of natural gas when temps approach 20 degrees and electricity becomes very expensive. ( the gas plants have to switch to diesel so that pressure can be maintained for NG heating customers). Also heat pump output diminishes below 40 degrees, regardless of technology, there is just less heat available in the air.

I don't have time to calculate the numbers right now but I don't think the difference is as great as that link alludes.

Your supposed to input your own values based on the current price of fuels, then hit calculate...

[ITD]

Originally Posted by ishoot308

Your supposed to input your own values based on the current price of fuels, then hit calculate...

I understand, for most of the systems listed, the efficiency is pretty constant regardless of outdoor temperatures. For a heat pump not so much. It is very difficult to find this info is the Mitsubishi web site. Most of the pertinent data is apparently in the technicians side of the website, I'm not sure I can get to that info, it certainly hasn't been easy to find. But they do put a sample table at the end of one of the brochures. I'll transcribe below.

at 32 degrees this unit produces 16,469 btus
at 14 degrees it produces 13,453 btus
at 5 degrees it produces 11,260 btus
at -4 degrees it produces 8,970 btus


This is fine if the system is designed properly, but it definitely affects the efficiency..... I would feel better about the link you provided if it disclosed how they got their numbers.

Here's where I found mine:

http://www.mitsubishipro.com/media/3...actorguide.pdf