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PaleMelanesian 09-16-11 04:50 PM

New central AC / heat pump next week!
I'm being proactive and replacing our system before the old one fails. This way I get to choose what I really want and not just what's available at the moment.

The old system is 20 years old. It's probably a 10 SEER, but I have no way of knowing. Our peak summer electric bills are 1800-2000 KWH / month. (this summer we topped 2500, but it's been the all-time hottest summer on record)

I'm paying to have it installed. I've rebuilt most of this house and I've had enough of it for a while.

Minimum available now is 13 SEER for $5000. We're getting a 16 SEER for $7000 instead. I estimate the difference should pay for itself in 6-7 years. That's still within the 10-year warranty period. Also available is a 23 SEER iq system for nearly $11,000. While it would pay back in about 10 years, we decided to go mid-level and spend the extra money on improving the house's efficiency instead.

The attic needs ventilation. It has a few turbine vents and nothing else. No ridge vents, no eaves vents, no gable end vents. That's the first project. I have already upgraded the ceiling insulation. Maybe next would be radiant barrier on the underside of the roof.

Ideas for other efficiency improvements? The house is 2400 sq ft, single level, pier and beam. All electric, no gas. Dark shingles that don't need replacing for years to come. Roughly north-south ridgeline with attached garage on the south end. Winter heating (also from the heat pump) is nearly as big a cost as summer cooling.

Daox 10-14-11 08:20 AM

I was trying to find an older thread of mine and came across this. I must have passed right over it.

How did the install go and how have you been liking the new unit so far?

If your main energy sink is cooling the house I'd definitely get some radiant barrier up and improve attic ventilation. I'd also do as much air sealing as humanly possible (as always).

PaleMelanesian 10-17-11 08:43 AM

I'm pleased with the install. The guys were very professional. They took time to reroute the drain plumbing for better drainage and added a cleaning port. They reinforced the closet floor where it was sagging. They stayed past dinner to finish the job the same day.

The unit - blows a lot more air, so it's louder. I added a second air return in the next room to relieve some restriction and noise. The air it blows is colder. That means it cools MUCH more effectively than the old one. I could tell within 5 minutes. The outside unit is much quieter, which is nice.

The weather has been mild so I really can't tell about power usage yet. I expect major savings - about 3/4 of our electric cost is heating/cooling. If this knocks a third off that, it'll be 1/4 off the total bill. :)

Adding ventilation is next. I bought some sample ridge vents to study and inspect.

AC_Hacker 10-17-11 11:32 AM


Originally Posted by PaleMelanesian (Post 16840)
Adding ventilation is next. I bought some sample ridge vents to study and inspect.

Have you looked into moving some of your heat producing appliances out of the living space?

Where is your water heater located? It leaks heat year-round. I might be better off in the garage.

Have you considered a fully equipped patio kitchen? Kind of a modern day cook-house.

I saw a really pleasant one in New Orleans, with an old refrig, stove and sink duplicated outside for the summertime. Very pleasant with loads of plants, and cages for parrots & pythons. Much cooler than inside.


Daox 10-18-11 11:00 AM

Wow, thats very impressive. Do you have anywhere online (visible to us) where you track your energy usage? (Sorry, still no energy tracking available here)

PaleMelanesian 10-19-11 08:26 AM

I don't have a public log of my usage.

It varies from 500 kWh/mo in spring/fall to 2500 in summer and up to 4500 in winter, average is about 2000. 500 is the constant usage from water heating, cooking, refrigerator and lights. That leaves 1500 in variable usage due to HVAC. The new system is 16 SEER compared to the old one (probably) 10 SEER.

The winter spike is due to the old heat pump not performing well below 35F. We had to switch to resistance heat at about 3x the consumption. This new unit has smart defrosting as well as being more efficient so it should handle much lower temps.

We have a programmable thermostat, but it doesn't do a whole lot. 3/5 of the family is home all the time.

PaleMelanesian 12-06-11 08:21 AM

After a couple mild months, the first real month of results came in - kWh is down 25% from November 2010. :D Just as the estimates said it should. It turns out you can make decent estimates from the SEER ratings of the old and new systems.

Originally Posted by PaleMelanesian (Post 16840)
it'll be 1/4 off the total bill.

gasstingy 12-22-11 07:40 AM

I'm glad I stumbled across this. The improvement in efficiency you've realized is most impressive. I keep kicking myself for the way I bought the central unit in my house. I have a 12 SEER AC unit combined with a gas pack for heat. The gas pack is bottom of the line 77% efficient. :o

It's somewhere on my to-do list to replace and I keep thinking how a geothermal unit would be great. {Except for that big pricetag :eek:} Whatever I do when the time comes, you can bet I'll pore over every thread I can find here on the topic.

PaleMelanesian 04-16-12 01:36 PM

I spent this winter's savings on ventilation. The house is 2400 sq ft. It was previously vented by four turbines, and nothing else. That's about 4 sq ft. I put ridgeline vents wherever possible and added about 15 sq ft of free vent area. That should help a little bit when summer comes.

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