So my house had a old almost 25 year old, 1.5ton central air unit. It worked but was slow to cool the house down. We figured okay its almost 25 years old, time to replace the beast.

So on June 24th we had it replaced with a brand new, 2 ton (since the hvac guys said the old one was too small at 1.5 ton) central air unit along with all the new parts needed for inside the furnace.

Instantly we could tell the new unit was working better than the old one. It would cool the house down faster and not run as long it seems. The old one would take close too 2 hours and 30 minutes to drop the house just 5 degree's where as the new one was around 1 hour and 50 minutes to do the same. So not crazy faster than the old one but definitely faster.

Fast forward 3 weeks. July has been a very warm month so far and thankfully i can check my daily hydro use by the hour on hydro one's website. And from what i can tell, the new ac unit is burning about as much power as the old one. Even though the new one is newer and a 13 seer as opposed to a 6 seer (maybe it was an 8, i cant remember).

How is this possible? i was told by many people (not just the hvac guy) that the new one would be way more efficient. I cant go back to last years hydro usage to compare since hydro was cheaper then, so its hard to make a good comparison. But i can however compare a very hot day in june to a hot day in july and the energy usage is roughly the same.

This makes absolutely no sense to me. We knew it wouldn't be crazy cheaper to run, but right now its not looking like spending the $3.2k to have it replaced was worth it.

Please tell me im just being paranoid and it really is cheaper to run? and that it has **** to do with the weather? cause from what i can see... its maybe only a few cents cheaper to run than the old one..... doesn't seem like it was worth it.

The only thing we can see is that it really is more efficient at doing its job than the old one. With the old one we avoided cooking in the house whenever possible cause it would make the central air unit constantly run for a good hour and a half or so just to drop the house a few degrees that it might have went up due to the cooking. The new unit, i haven't timed but i can tell its a **** ton better. But again, it seems to still burn alot of hydro. why? there must be an explanation for it that i cant think of... please help me justify in my head that spending the $3.2k was worth it!

Edit: Not to mention my lights dim for a split second whenever it kicks on. Old AC unit never did that. And all my lights are LED to boot!!

 

Is it possible that you are getting more cooling for the same money? If you avoided cooking in the house before because it got too hot but now you can do so comfortably, it seems that you are getting more for your money. If you used your new cooling system just as you did you old one, you might see a cost savings but since you are taking advantage of the fact that it does a great job cooling, you are actually using it more than the old one.

- Peter

 

Mind = blown...

You could be onto something there actually, however.... We still tend to avoid cooking in the house whenever possible due to the fact it will make the ac run more than it needs too. However there are times where we do it just because we simply can now.

Also our old one we had set at 24 celcius instead of 23 because it took so damn long to cool the house down before, so maybe that extra degree is making a big difference... hmmmm, food for thought i guess.

But why would the new one make my lights flicker for a brief second whenever it kicks on compared to the old one?

 

Don't know what humidity is like in your part of the world, but cooling when the air is humid uses more energy than cooling when air is dry....that may explain your June vs July comparison.

It takes quite a bit of energy to remove water from the air (which the AC does while it's cooling) so it can be a significant difference.

You should be able to look at KWH usage between last year and this; that would take the price per KWH out of the equation. And most utilities provide degree day figures so you can factor in differences in average temperature.

 

It is NOT just the temperature; the wind velocity & infiltration rate of both temp & humidity can make a huge difference.

However; do not expect to save a lot of money due to SEER differences; too many factors tend to keep that from happening.

Tested delivered-performance to the rooms will reveal some hard realities...!

 

A few years ago, my AC was doing the same thing. Everytime the compressor kicks on, the lights would flicker. Ever since we had a hard start kit installed, I believe it resolved the problem. Do you know if your old system had an hard start kit?

 

I have no idea if a hard start kit was installed.

I think the problem is coming down to this unit is a half ton bigger than the old one, which is using more power but doing a more efficient job compared to the old one.

 

Up-sizing raises energy consumption.

It's normal for a unit to take a long time to cool the place down, they're sized to maintain the setting.

Also if your ducts are only sized for 600 cfm or 1.5 ton (common in really old houses build for an inefficient furnace, no a/c) the 2 ton may be getting marginal airflow.

But yah, if you're now maintaining 23 and before it was set to 24, possibly drifting up in hot weather, the new one is doing more cooling.

Same goes for airflow. With a new unit pushing more air it could be cooling distant rooms better which increases heat gain.

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A 25 year old a/c could very well be in the 8 to 10 range.

6 or 7 seer would be one dating pre-1980s.