Energy Improvement Results

The new HVAC system was installed this week and on Monday they put in the new insulation in the attic and did all of the air sealing, including fixing the attic door and sealing the house fan. Today they ran a follow-up blower test to see what difference all of this made. They had missed a couple of things on the first pass, so they sealed around the ash dump door in the back fireplace and installed some weatherstripping on a door. They said the air leakage had improved by 30%. That didn’t seem like that much to me since the house was very leaky before. One thing we found was that a lot of air was leaking from the back room which has wood paneling. Apparently, air was being sucked down from the attic of the back room, down the walls, and out the joints of the paneling. The only way to seal that would be to caulk all the joints of the paneling, overlay the paneling with drywall, or replace the paneling. That would be great, but that’s more than I want to do right now. You could feel a breeze blowing from those joints, but they also had a pretty powerful fan sucking all of the air out of the house. There wasn’t a way to seal from above because that room has a low flat roof that isn’t accessible.

The supply and air vents were measured for air tightness as well. The reading is supposed to be below 1.0 for each vent and there were a couple that were higher than that. Part of that may relate to the way the “boots” for those vents fit into the wall opening, leaving a small gap that lets in air from the crawlspace. The HVAC guys didn’t really mess with the boots at all, just tied their ducts into them. I will see if they can make some improvements to that, though I think that is kind of beyond the scope of their work. The guys that were here today did caulk the worst one and brought the value down a little.

Even with all of the leaks, their software calculated that I could save about 28% on my energy costs, qualifying me for a $1450 rebate from Georgia Power. If you can get to 30%, you can get an extra $400 rebate from Georgia Power. So they started trying to figure out ways to get another 2% that would cost less than $400. One idea they had was a water heater blanket which would bump it up another 1% and would cost $100. They asked how many incandescent bulbs I had in the house, but I don’t have any, so that wasn’t an option. I asked if they had entered the SEER value of the new air conditioner at 15.7 SEER. They had included the original work estimate which included only a 13 SEER unit. The condenser I have is actually rated at 14 SEER, but the installers were able to tweak it and get up to 15.7. Just to be safe, they entered 14 SEER and got just over 30% savings to 30.2%. Then we were talking about rebates and I mentioned I could get a Georgia Power rebate for half of the price of the thermostat they had installed. This turned on a light for them, so they said that was something they could enter into the software. With that thrown in it went up to almost 34%. I had a programmable thermostat before but I think the software model may not take that into account, or it could be that a manufacturer’s thermostat will just operate the equipment more effectively than the old one I had from Home Depot (which was a pretty old model). I think that would be more true with the variable speed systems than mine, but I don’t really know. It’s all theoretical since they can’t measure actual savings without waiting a year and seeing what happens.

Anyway, there is no way the rebates and tax credits will come close to paying for all of this, but overall efficiency rebate paid for about half of the attic and sealing improvements (though a lot of the overall efficiency was due to the HVAC system and new ductwork). And even though I don’t pay that much for heat and air conditioning, I think I should see a significant change in my power and gas bills.

4 thoughts on “Energy Improvement Results”

  1. I *finally* got the whole house rebate for $1850 from Georgia Power. It took longer than it was supposed to, but after talking to a Georgia Power person they said there was maybe some missing information from the original submission that held it up. I also got a $100 rebate for my thermostat last weekend, which took about 3-4 weeks (submitted by me).

  2. The new air conditioner is definitely more efficient than the old one, but probably not as much as I hoped. Looking at electricity consumption during June, July, August, and September for the 4 years before and after the installation, I saved about 20% or a 4-year total of 2,341 kilowatt-hours (about $367 using 2021 prices). However, the new system definitely uses more electricity during the winter. I’m not sure why that is, but I would guess that the new furnace doesn’t get as hot and therefore runs longer to heat the house. Or maybe the flexible duct isn’t as efficient as the old metal ducts causing the blower to work harder. Anyway, looking at electricity consumption during December, January, February, and March for the four years before and after the installation, I see an increase in winter electricity consumption of 25% or 1,191 kilowatt-hours (about $228 using winter prices which are higher per kwh if you divide the bill by the kwh used). So more than half of my electricity savings on air conditioning are being used by the furnace in the winter. Looking at natural gas savings, the new furnace saves 30% or 1050 therms total (about $1,154). So ultimately the new system does save me money, much more on heating than on cooling, coming out to a net of about $323 per year.

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