Getting a more efficient heat pump

[Jud McCranie]

I'm trying to estimate how long it would take to recoup my investment if I buy a more efficient heat pump.

The one we have is 11 years old and has a SEER of 10.05. It is a

4-ton unit for about 1975 square feet and the real estate agent said that it was oversized, so me might could use a smaller one.

I got my monthly electric bills for the past 12 months. We used a total of 27,100 kWh, at a cost of $2,574. Our rate depends on the season and also on how much you use in a month. Summer rates are higher, and the more you use, the more it cost.

There are periods in the fall and spring where very little heating and cooling is used. Our smallest bill was in November, using 1600 kWh, at a cost of $129. If I assumed that this used no heat/cooling, that means that heating and cooling came to 7,900 kWh, or $1026.

Does that look like I could recoup my investment in a more efficient heat pump in, say, five years?

[Robert Allison]

Your real estate agent also does air conditioning?

Let the HVAC guys size your unit. That said, savings depend upon a lot of factors, far too many to review right here. You can get an idea of the savings based on the chart at this site:

Just upsize by 25% and that should tell you what you want to know.

[Tony Hwang]

Hi, If that pump has been running well, it has few more years life left. B4 you decide to spend for upgrading, how about air tightness(insulation) of your house? SEER 10.5 is of course outdated to today's standard but to get real improvement you have to deal with whole package, not only one component of a system.(like air handler, etc.) What is your electric rate? I pay 7 cents/KWh.

[OLDHVACDUDE]

A real estate agent is in no way, shape, form or fashion qualified to say if a heat pump is oversized. call a licensed hvac contractor and have the m do a manual J load calculation. That is the ONLY way you will know for sure.

[CJT]

From that page:

"The following data is based on a 3-ton system (36,000 BTUH) at 9 cents per KWH at 2800 annual hours of use."

2800 annual hours of use? I hope they don't mean that's how many hours they assume it runs in a year. Even on a hot day here in Texas, our unit only runs about 10 hours. And while it's warm here much of the year, the heavy AC season is only about 4 months long. Maybe if I have some spare time, I'll add up the minutes our AC ran last year (I have it instrumented); I'm pretty sure it's nowhere near 2800 hours.

[<kjpro]

The best way to figure operational cost is too use the areas Cooling/Heating degree days and know what size unit you are going to be operating. Have that and the cost of your utilities, you can get very close to the actual operational cost.

[CJT]

I realized I could get at the number another way (I know about how many KWH I use for cooling each year, and about how many watts the AC and air handler consume while running). In a year, our AC runs about 1600 hours. 2800 seems way high to me.

Austin, Texas

[CJT]

FWIW, our peak day this year was August 12. Our AC ran for 11 hours 40 minutes.

[<kjpro]

Straight or in a 24 hr period?

[CJT]

In a 24 hour period, midnight to midnight.

[<kjpro]

I hope that wasn&#39;t at design temperature.

[Robert Allison]

Ours runs pretty much one hour on, one hour off in the summer, which lasts about 9 months here in central Texas. It gets down to about 85 at night in the summer, so it is on even then, just not as much.

So, 270 days of cooling at 12 hours a day equals: 3240

[Bob]

I&#39;m not an a/c person, but as a home owner, just had recent experience. Our 11 year old A/C - heat pump went out and we had it replaced; the outside unit, the air handler in the attic, and larger return air vent pipe. (We had 16 inch and the A/C people recommended 18 inch). All in all the whole thing was $7,300. Our next month electric bill was less by $80.00. There could be other factors involved in that as well, but no doubt it was cheaper.

It would take a very long time to pay for the new unit with the savings, so if that is why you are considering it, I doubt it would be worthwhile.

One more thing, there are two types of Freon units. (I forget the numbers). The old type is going to be discontinued in a couple years and the price will sky rocket like the old style auto Freon. I&#39;d suggest that if you get a new unit that you get the new Freon type. Bob-tx

[Jud McCranie]

It varies according to the season and according to how much you use. It is higher in the summer. The first 1000 kWh are one rate, then it goes up. Then it goes up again at 2500 or something like that. I think the top rate is over 10 cents / kWh and we hit that in the summer.

[Tony Hwang]

Hi, I see. I live up here in Calgary Alberta. For next 5 years my rate is locked in at 7 cents per KWh. If ever rate drops(most unlikely) I can cancel the deal any time with two months notice. Right now going rate is 11 cents.

[Tony Hwang]

Hi, Like old R22 vs R410a something like that? Carrier calls it Puron. R22 equipment won&#39;t be made after 3 years from now and R22 production will diminish slowly in next 30 years or so I heard. Our a/c runs on Puron.

[trader4]

If his total yearly estimated electric bill for his heat pump to heat and cool his house is only around $1000, I think it&#39;s very unlikely he&#39;s going to save enough in electricity to justify getting a new higher efficiency unit.

[Jud McCranie]

Thanks for the recommendation of the chart.

It is hard for me to trust HVAC people on such matters. Last year my parents got new units for two houses. One has two stories, six bedrooms, 5.5 baths, and seven other rooms and they sized it at 2 tons. Now the inside of their house is mildewing because it can&#39;t keep it cool or dry. The other house is one small story, three bedrooms, two baths, 2 other rooms, and they (different person) sized it at 4 tons. I told my parents that, if anything, they should have put the 4 ton unit in the big house and the 2 ton unit in the small house.

[CJT]

All you need to do is hang around here for a while (or, better still, alt.hvac) to know that there are plenty of alleged "professionals" in the business who don&#39;t know squat.

[Moe Jones]

They first should have gotten a heat load on both homes to show them what proper size was needed.