game of chasing SEER

[PoorOwner]

Hey guys, I have been shopping and comparing SEER, I even looked at the engineering manuals to see the power consumption during various indoor / outdoor conditions.

For my comparison shopping for 9K BTU, to be consistent lets keep it within the same brand. Mitsubishi, they have a 24.6 SEER and a 18 SEER for 9K models. My cost difference was about $550 more!

The 18 SEER is dumbed down a little on features but nothing I will miss. The evap is nearly the same CFM, coil everything.

comparing the units, the 18 SEER only uses about 170W more at full BTU output.. Like (760W vs 580W). But at lowest output BTU, uses 240W they are actually the same, I assume maybe closer to the load I will be operating once in modulation mode for most of the day.

I checked Mr Slim came out around 2010 with 18 SEER and people were really happy.

Just for kicks, I checked 24K engineering table. Now the efficiency on this bigger units are starting to have a bigger gap, about 800W more at rated capacity of 24K BTU (18 SEER vs 20.2 SEER on the fancier model) now how can the seemingly minor "2" SEER change the power so much?

I know there is HSPF rating also for heating, it seems to tell you how well it will heat as the outside temp goes down.

So what do you think chasing the SEER game is good or not? what SEER is acceptable and what's not? it's like prepaying money for efficiency. And, I don't know if this is true or not, but I heard the higher SEER runs on thinner walled copper coils and are more prone to perforation and leakage over time.

 

[Fix Until Broke]

SEER is Seasonal Energy Efficiency Ratio - key word here is Ratio.

Simply the ratio of energy moved to the energy it took to move it. The larger unit takes more energy so 2 SEER makes a bigger difference than on a smaller unit.

All the details can be found here

https://en.wikipedia.org/wiki/Seasonal_energy_efficiency_ratio

You can do the math on the upfront premium to get an additional 2 SEER points vs your cost of energy, usage, etc and determine if it's worth it to pay the premium up front for lower consumption or not.

 

[Done That]

There are a variety of ways a mfg can increase SEER, many having to do with minimizing pressure drop such as oversize the reversing valve or straight thru ball valve service valves instead of right angle, more coil, multi row coil. Anyway, I would avoid the generalization about thin wall tubing, plus it had to pass a UL burst pressure test.

Carrier just released a 42 SEER 9k btuh ac unit at a recent industry trade show. 18 is going to seem "low" in just a few years.

 

[TangoFoxTrot]

When you start getting into units with over 18 SEER, the actual cost savings really start to drop off as you go further up. It's like comparing an LED light bulb that uses 9 watts vs 11 watts.

Here's an interactive calculator for SEER, don't know how accurate it is as there are so many variables, but if you plug in an 18 SEER vs 24 SEER comparison, it's giving like $4 a month in savings.

https://www.lennox.com/buyers-guide/tools/energy-savings-calculator


If an 18 SEER is both simpler and cheaper to purchase than the highest end 24+ SEER model, I would probably lean towards that.

 

[Jackfre]

Weh the inverters units first came out i spoke with the Japanese engineers and they were saying the seer was actually much higher than the US ratings showed. They simply did not know how to test a modulating piece of equipment. the mid-20 seers were actually in the high 30-low 40's even back then. I am not sure how they test them today, but it looks like Carrier decided to claim the marketing advantage. I believe Toshiba makes the Carrier units. Over the years, Toshiba has, for a short time in the early '00's, been in the market under their own name and since has been private labelled under a variety of brands, finally settling with Carrier. A good move on their part.
I would go with the highest efficiency unit of the brand you are comfortable with. Remember you are dealing with PG&E and it will never work out to our advantage. The other reason to go high seer is that is where the high hspf resides as well and you will love the heating side of the unit.

 

[PoorOwner]

To be honest I don't know why Mitsubishi is push out a 18 seer line, in 2017.
It claim it to be an economy line. (so they know their unit costs a little on the high side) Probably to use old tooling to remake the Mr Slim units. In fact I was just going to get a pioneer or one of the Chinese ones that has 16-18 seer, but the Mitsubishi caught my eye with their value line.

Mitsubishi is very traditional and reflects Japanese engineering, very conservative with risks, aesthetics not a priority.. but they make their units and electronics reliable and just works well. You can see with their wifi add on options they are not first to market, in fact a bit behind and cumbersome.

One thing I see the Chinese ones are doing, they claim to be are using "threaded" copper tubing that is twisted like a screw. (not in the lineset though) Claim to increase efficiency -- more surface area ?

 

[rlitman]

...One thing I see the Chinese ones are doing, they claim to be are using "threaded" copper tubing that is twisted like a screw. (not in the lineset though) Claim to increase efficiency -- more surface area ?

Part surface area. But I think it has more to do with turbulent flow. It causes mixing of the refrigerant in the stream, rather than allowing for a boundary layer. I see similar performance quotes for the use of chevrons in flat-plate heat exchangers.

 

[aunsafe2015]

Carrier just released a 42 SEER 9k btuh ac unit at a recent industry trade show. 18 is going to seem "low" in just a few years.

Wow. 15 hspf as well. Anybody know the COP figures?

Have there been any significant improvements in multi-zone mini splits? Seems like a decent number of single zone units at 30+ seer, but hard to find a multi-zone unit much above 20. Is that some sort of a technical limitation, or should we hope to see improvements for multisplit as well?

 

[finn]

When you start getting into units with over 18 SEER, the actual cost savings really start to drop off as you go further up. It's like comparing an LED light bulb that uses 9 watts vs 11 watts.

Here's an interactive calculator for SEER, don't know how accurate it is as there are so many variables, but if you plug in an 18 SEER vs 24 SEER comparison, it's giving like $4 a month in savings.

https://www.lennox.com/buyers-guide/tools/energy-savings-calculator


If an 18 SEER is both simpler and cheaper to purchase than the highest end 24+ SEER model, I would probably lean towards that.

21 seer gets you a $1500 rebate here, if you are replacing electric heat.

 

[JazzBlueRT]

When you start getting into units with over 18 SEER, the actual cost savings really start to drop off as you go further up. It's like comparing an LED light bulb that uses 9 watts vs 11 watts.

Here's an interactive calculator for SEER, don't know how accurate it is as there are so many variables, but if you plug in an 18 SEER vs 24 SEER comparison, it's giving like $4 a month in savings.

https://www.lennox.com/buyers-guide/tools/energy-savings-calculator


If an 18 SEER is both simpler and cheaper to purchase than the highest end 24+ SEER model, I would probably lean towards that.

I went from an 18 SEER to a 22 SEER and saved $100 per month on my electric bill over the summer. That was in South Florida. The system was an IQ drive with separate humidity controls. The lower humidity let us keep the stat at 78 instead of 76 probably accounting for the substantial savings.

 

[JazzBlueRT]

Weh the inverters units first came out i spoke with the Japanese engineers and they were saying the seer was actually much higher than the US ratings showed. They simply did not know how to test a modulating piece of equipment. the mid-20 seers were actually in the high 30-low 40's even back then. I am not sure how they test them today, but it looks like Carrier decided to claim the marketing advantage. I believe Toshiba makes the Carrier units. Over the years, Toshiba has, for a short time in the early '00's, been in the market under their own name and since has been private labelled under a variety of brands, finally settling with Carrier. A good move on their part.
I would go with the highest efficiency unit of the brand you are comfortable with. Remember you are dealing with PG&E and it will never work out to our advantage. The other reason to go high seer is that is where the high hspf resides as well and you will love the heating side of the unit.

I had a IQ Drive system in my previous home and that system was awesome. That was an inverter system and was very quiet. I would definitely buy this system again.

 

[Jackfre]

COP is very high across the operating ranges, but not a meaningful comparison to conventional central heat pumps, which are single stage. Given that todays mini-splits are all inverter, or modulating it is difficult to do a straight comparison. Trying to do one would I think show that the mshp's are much more efficient, AND THEY ARE NET TO THE SPACE, with no distribution or duct losses. Also, and my info on this may be somewhat dated, I believe that conventional heat pump COP's are a single measurement at 17* & 47*.

 

[Falcon67]

I think - trying to remember - that we went with 14 SEER. 18 was marginal savings for bunch more $$$$. Not worth it.

 

[HAP]

One thing to consider is repair costs. There is usually some technology involved with attaining the higher SEER. Variable speed blowers and inverter technology are significantly more costly to repair/replace. No more $200 blower/fan motor replacements on those models. More like $900...

R,
HAP

 

[DC73]

One good thing to do is get prices on all SEER options and then look for where the price change per SEER no longer seems reasonably incremental.

For example if 15 SEER is $100 more than 14 SEER and 16 SEER is $100 more than 15 SEER, but 17 SEER is $500 more than 16 SEER, then very likely your best bang for the buck is the 16 SEER unit.

DC

 

[HAP]

I would use this basis as well.

One good thing to do is get prices on all SEER options and then look for where the price change per SEER no longer seems reasonably incremental.

For example if 15 SEER is $100 more than 14 SEER and 16 SEER is $100 more than 15 SEER, but 17 SEER is $500 more than 16 SEER, then very likely your best bang for the buck is the 16 SEER unit.

DC

 

[yeldogt]

With mini splits -- they are all inverters. It's math. How much will I save with "X" vs "Y" ... have to make sure you are comparing equal specifications. You can't price a hyper heat and compare it with one not having the ability to work at very low temps .. especially if you need it. After that it's a question of rebates on the better equipment/ worth of going with the better brands .. and needed options.

With a home unit -- when you get to 16/18 seer the technology changes to multispeed compressors and VS blowers .. and continues from there to full VS compressors as you move up. It becomes a comfort reason for buying them as much or more vs saving money .. often you never save any money.

in a shop situation you don't really need the best mini split head unit with an electric eye ..

 

[theoldwizard1]

Carrier just released a 42 SEER 9k btuh ac unit at a recent industry trade show. 18 is going to seem "low" in just a few years.

That is a very impressive number ! I am far from an expert but this is what I have observed:

• The high SEER (>25 SEER) mini-split do not have much capacity. 9,000 BTU seems to be the "sweet spot".
• Multi heads/air handlers kills SEER.

If you can afford it, 2 or even 3 very high SEER (>30) may pay back i a reasonable amount of time. One big reason is that in the spring/fall months when there is a low heating/cooling load, you can typically just turn off the second and third unit. Even in summer/winter if you can close off parts of the house, you may not have to have all units running !!

 

[mrpizza]

I was looking at an 18 and a 20 seer heat pump for my house. The Ahri certs showed the eer and hspf were the same, just the actual seer was 1.25 higher on the 20 seer unit. I bought the 18.

 

[rattle_snake]

Not sure how accurate these online calcs really are but fun to play with (math is fun, right?)
https://kobiecomplete.com/cool-tips/seer-savings-calculator/

For limited use, like a shop compare to a home, the payback times are pushed out pretty far.

 

[rburke65]

Oh had to be at least 15 years ago I'm thinking that we replaced our central air with a heat pump with a seer of 13! Things have changed a lot!

 

[6768rogues]

I never buy the latest most energy efficient equipment. We just bought a new system for our FL house and got 16 SEER. Typically new high effeciency units have proprietary parts and fancy controls that are not proven over time, are expensive, are hard to diagnose and are probably not in the repairman’s truck. There is a finite number of ways to compress refrigerant and expand it in a coil. Much of the high efficiency is from fancy controls. That translates to expensive to maintain.

 

[theoldwizard1]

Typically new high effeciency units have proprietary parts and fancy controls that are not proven over time, are expensive, ...

There is a wide "middle ground" that you chose to undershoot.