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 markdaviss1 06-14-2011 12:30 PM

Question on HSPF

Hello! I'm considering replacing my electric baseboard heat with hyper-heat mini-split systems. The particular Mr. Slim (Mitsubishi) heat pump I'm looking at has a HSPF rating of 10.55, and heats down to -13 degrees F.

I understand that electric resistance has a HSPF rating of 1.0, but it seems impossible that any system would produce 10.55 times as many btu per watt used. Is it possible? Can/should I expect something like a 90% reduction in my electric usage for heating?

Any info will be appreciated!

Mark
Muncie, Indiana

 zootjeff 06-14-2011 05:53 PM

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You are confusing COP and HSPF. Electric heat has a HSPF of 3.41, or your not doing the conversion from BTU to watts.

You take the COP and you divide by .293 to get HSPF. Resistive heat is 1/0.293 or 3.41 HSPF..

COP equals energy moved divided by energy used.

If your HSPF is 10.55, then your COP is 3.09 or 3 times the input power gets moved.. Which is quite reasonable. You should see about 1/3 the energy usage you had before. Resistive heat sucks.

Quote:
 Originally Posted by markdaviss1 (Post 667211) Hello! I'm considering replacing my electric baseboard heat with hyper-heat mini-split systems. The particular Mr. Slim (Mitsubishi) heat pump I'm looking at has a HSPF rating of 10.55, and heats down to -13 degrees F. I understand that electric resistance has a HSPF rating of 1.0, but it seems impossible that any system would produce 10.55 times as many btu per watt used. Is it possible? Can/should I expect something like a 90% reduction in my electric usage for heating? Any info will be appreciated! Mark Muncie, Indiana

 markdaviss1 06-14-2011 08:37 PM

Thanks, zootjeff! I actually found that same information (on wikipedia) after creating my original post. But it's nice to have someone confirm for me that I was properly interpreting what I was reading.

And I certainly agree - a HSPF rating of 10.55, for a COP that's (as I calculate it) right at 3 times that of electric resistance, would quickly justify the investment in the more efficient system.

 zootjeff 06-15-2011 01:14 PM

59 Attachment(s)
Quote:
 Originally Posted by markdaviss1 (Post 667482) Thanks, zootjeff! I actually found that same information (on wikipedia) after creating my original post. But it's nice to have someone confirm for me that I was properly interpreting what I was reading. And I certainly agree - a HSPF rating of 10.55, for a COP that's (as I calculate it) right at 3 times that of electric resistance, would quickly justify the investment in the more efficient system.

Are you amazed that you didn't do this sooner, or that you didn't know that this was an option? I'm amazed how few people know about heatpumps.. I was certainly baffled when I discovered that I could install a heat pump for 300 bucks more than AC and save 2-300 bucks a year. Why didn't someone tell me sooner?

The contracters that gave me quotes, pushed a specific kind of system and shy'd away from heat pumps.. Lame.

 markdaviss1 06-15-2011 02:14 PM

zoot: Ours is a farmhouse built in 1880. It has no existing ductwork. It has been remodeled and additions added several times, so it's your typical old farmhouse, hodge-podge floorplan - some is on a crawlspace, some is on a slab, etc.

I got quotes for anywhere from \$12,000 to \$16,000 to add central air/heat, with much of that expense going to installing ductwork.

I've known about mini-splits for some time but have been scared off by the fact that they, prior to this new hyper-heat technology, shut down at something like +17 degrees. I knew we'd need to keep our existing electric baseboard, which I was trying to avoid, and to continue to pay for electric resistance whenever the temps got low - and here in Indiana we have several weeks each year when the high temp might only reach 15.

It now appears that I might be able to heat/cool the entire house (currently only partially cooled by two window a/c units) by installing four 23 SEER/10.55 HSPF mini-split units for around \$1,500 each. It's possible that I'll experience full payback within 5 years AND pick up a/c of the entire house.

Every few years we might experience one night with an overnight low of less than -13 degrees. If/when that happens, I guess I'll fire up a couple of kerosene heaters to protect the plumbing, and my wife and I will go visit one of the kids!

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