Heat pumps: operating cost vs efficiency?

19 years ago

Background: We have an old house that needs an entirely new HVAC system, ductwork and all. We've definitely decided on two heat pumps (one for 1st, one for 2nd/3rd floors) because of the ducting issues. We've narrowed it down to one contractor. We have two proposals: One is for Carrier Comfort series, 15 SEER, 8.5 HSPF, the other is for the Carrier Infinity series, 19 SEER, 9.5 HSPF.

(here's a link to the carrier website with the info on both)

I don't know how to evaluate the difference in cost (which struck me as quite high - almost $6k more for the two higher efficiency systems) without knowing how much of a savings we'd really likely see with a much more efficient system. Or rather, TWO much more efficient systems, since we're being like the doublemint commercials with this install.

Does anyone know the equation used to figure this out -- given a specific electrical cost and a guestimated usages and whatever other info relates, how much would a higher efficiency system save us over time?

FYI, in case it matters, we're in a fairly moderate climate - Mid-Atlantic, so generally not hideously cold or hot (though it gets very humid). We're getting humidifiers, thermidastats designed for heat pumps, and higher-end filtration.

Thanks.

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Comments (8)

tanama
Original Author
19 years ago
Also fyi, each of these heat pumps is two tons.
bob_brown
19 years ago
IMO, higher SEER equipment is a joke. The money spent on the equipment will never pay for the higher cost. In a mid temperate zone, it is difficult to justify anything better than basic equipment. If designing from the ground up, I can see a benefit in higher SEER junk. But not too much benefit. SEER is not a consumer friendly measurement. It saves peek power. This is a concern for utility companies. In De I would expect higher than average labor prices, but not more than $10k per system from the ground up.

I am replacing a 3 ton system next week. I have been looking for used equipment, but cannot find the electric furnace. The total job will be less than $2.5k. I am at the bottom of the price structure, but this will include new lines, inside and outside units. I will spend about 1 day doing the job. The investor can spend $10k for a job or $3k. The house will sell for the same price.
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xracer
19 years ago
in an old house take the 6k and put in insulation then you will see savings.
baldloonie
19 years ago
xracer makes good sense!
tanama
Original Author
19 years ago
The house was already stripped to the studs, insulated in all the walls, the roof/attic, the crawlspace, double-pane glass... now if the previous owners who did that had only put in a new boiler instead of yanking out all the radiators and putting in electric baseboard heat, I'd be fine (I'd never make this investment just for central air).

The system I'm getting -- two each outside units, blowers, high-end filtration, humidifiers, thermidistats, and all the ductwork, with all installation costs, are just under 19k for the lower efficiency, mid-24k for the higher efficiency. Two $300 tax rebates from the IRS for the higher efficiency systems doesn't begin to put a dent in teh difference in price. I'm still not finding any equations to help but my gut's telling me that by the time I make up my money in energy savings, I'll be close to needing to replace those suckers anyway.

I still want to get that confirmed if possible.
mike13
19 years ago
Go to the Carrier website:

http://www.residential.carrier.com/knowledge/efficiency/ratings.shtml

Move the lightbulb from one SEER rating to the other & take the difference. For every $100 you spend you will save $46 when comparing the 15 SEER to an 8 SEER. Then drag it to the 19 SEER & you will find that you can save $59 when compared to an 8 SEER.

Thus, you would save $13 for every $100 spent when comparing the 19 SEER to a 15 SEER based on Carrier's information.

That's 13%. If you spent $100/month, that's $13 saved per month, $156 per year. At that rate it would only take about 40 years for the payback. What a deal !!!
mike13
19 years ago
Forgot to mention you can also use the HSPF lightbulb on the same page to do those calculations.
xracer
19 years ago
i would say you will save very little if any. i would go with the cheaper units and take the 6k and have a blower test run. then spend a little money on air infiltration work. an old house is bound to be leaky. i think you get a much better payback that way.