Knowing murphy, he will have me replace my ac/heater when I least want to do so. Current system is about 25 years old so it's about due (hoping to squeeze out another 5 years but won't be surprised if it pops smoke sooner).

I don't know what type of system I have (I see terms like ac, heat pump, etc and not sure what I really have - I need to research more). I have the condenser outside and the evaporator / propane furnace in the attic.

I think I have a 10-12 seer, 3.5T system (should be 5T if they sized correctly).

Currently, I can keep the desired temp during the summer while not expending more power than what solar covers (net meter for the year). My net electrical bill is about $200 for the year (would likely be $5000 w/o solar).

I don't see a need to pay for higher seer levels - the minimal available or something in the 12 -14 seer range should be plenty (iso- or a little better than what I have now).

Is there a reason I should still purchase a higher seer rating (like 18+ or something)?

I ask because previously (5 years ago), I was planning on a higher seer because it was somewhat price indifferent. But seems like prices have changed now and deltas between high and low seer are appreciable - even low seer seems expensive now. Just trying to make sure I have sufficient 'emergency' budget set aside.

You can use online calculators to show the delta of cost for SEER level. (similar to this one)

https://www.seerenergysavings.com

Basically, you can figure the cost of each unit, and the percent difference in operating costs.

So, if you have two units that are both 24000 BTU, and one has a SEER of 14 and the other is 20, it will let you know how long the initial higher cost for greater SEER will be equaled by savings over time on power.

Check your local codes first.

They require stupid high seer ratings in some places.

Seer2 is the standard since 2023.

My ac guy says it is diminishing returns on the ultra high seer ratings.

They are more complex and more prone to break.
Your local AC guy is the best person to talk to.

The installer is going to know how often he needs to service any particular unit.

The ROI is usually 10 to 15 years getting a higher seer. Unless the local cost of electricity is really high.

If your electricity is solar and vurtually free, that time could double.

Calculator here.

https://www.seerenergysavings.com/

Thanks! This is useful.

I'm estimating (based on a vendor website) that the replacement cost is about $14k (15seer) - $20k (18seer) - say average about $15k).

The delta in electricity costs is about 30% annually leading to an approximate break even point of about 10 years. Since in actuality I don't really have electricity costs (net metered out w/ solar), seems like it doesn't make sense to get higher seer (~$5k cost delta) unless there is some other benefit (higher seer is more reliable, more durable or some financial benefit other than electricty consumption).

Is there something else I should be considering?

If higher seer is actually less reliable and less durable, then it seems like that pushes me more toward lower seer since electricity consumption cost isn't relevant for me.

Note: I did some quick research and I don't think there is any benefit for a packaged system or heat pump. I think I have a split AC and regular gas furnace with a common air handler. Seems like I should just stick w/ that.

The complication is that my current refrigant lines seems like it's sized only for 3.5T; 5T would require larger diameter piping (not sure if that's possible or not w/ existing ducting - maybe it is but not sure how expensive it would be to route new copper piping). I may be limited to 3.5T system.

When I ran the numbers the higher SEER electric savings were not worth the extra cost of the unit.

Good to know - so considering electricity costs w/ or w/o solar, higher unit costs for higher seer is a hard ROI (breakeven 10+ years)...? And again, especially if they are more prone to issues / shorter life.

In any case, sounds like if I squirrel away about $15k, I should be roughly covered.

A couple of points.

First thing is to get one or more HVAC Companies perform a “Manual J” analysis. This will tell you what size you need in your particular situation. What you have now or what you think you may need (5ton?) is really irrelevant. Chances are that when you had the original system installed the HVAC contractor took the square footage of your home and divided it by 600 to come up with the number of tons (that was the divisor here back in the day.

Second point is if you live in a moderately temperate environment you may not even need a gas furnace. Modern heat pumps can actually work well into the 20’s thereby eliminating the cost associated with it.

In the energy efficient homes we built I would tell my clients that SEER ratings of between 16 and 18 were the sweet spot as the components weren’t bottom of the barrel (copper vs. aluminum) and my clients seemed to agree.

Thirdly your local utility and perhaps state and federal agencies may also offer tax credits or rebates. It would be worth checking out for their SEER2 requirements.

Thanks - good points.

1. I come up with about 5T using your formula. But how does volume come in (ie - how to consider 8ft vs 10 ft vs 12 ft ceiling height?)? Also, people in the neighborhood with smaller houses than mine have larger systems than mine.

2. Thanks - I don't really know what my options are. I'll look into a heat pump again. But my understanding is that heat pump is for both cooling and heating. It didn't sound like a heat pump would be sufficient for cooling around here (gets to be about 105F in the summer). And it only gets down to about mid-30s in the winter but sounded like furnace was more popular choice.

Yea, I'm thinking the lower end of that range is good for me provided components are copper and not alumimum. Cu is better than Al here, right? Or the other way around? In general, Al doesn't seem like a durable material to me.

3. I'll look into that.

Without knowing your location and how many days of the year you use a/c, your question cannot be answered.

Here a/c's last 12 years, if that. Yours is on way borrowed time.

quote:

1. I come up with about 5T using your formula. But how does volume come in (ie - how to consider 8ft vs 10 ft vs 12 ft ceiling height?)? Also, people in the neighborhood with smaller houses than mine have larger systems than mine.

That is exactly why you need to have a Manual J calculation done on your home. It takes into account the cubic footage of your home, the orientation, the windows, insulation as well as other factors.

In most new residential construction a Manual J is required in order to get a building permit and is useful in existing homes as well.

quote:

Originally posted by konata88:

...... I don't really know what my options are. I'll look into a heat pump again. But my understanding is that heat pump is for both cooling and heating. It didn't sound like a heat pump would be sufficient for cooling around here (gets to be about 105F in the summer). And it only gets down to about mid-30s in the winter.....

That seems like about ideal range for a heat pump.

quote:

Originally posted by jimmy123x:
Without knowing your location and how many days of the year you use a/c, your question cannot be answered.

Here a/c's last 12 years, if that. Yours is on way borrowed time.

Jimmy and anyone else who may be interested…
You can find that information on this site below. Just put in your location and it will tell you. This is part of the Manual J calculations also…


https://portfoliomanager.energ...degreeDaysCalculator