HVAC Resource Forum (HRF) - which system to get?

[clay]

Have a ~25 year old heat pump. Been nickel and diming parts and repairs for the past few years. Been considering replacement on our own terms, rather than mid-January in 10 degree weather or mid-July in 100 degree/75% humidity weather.

I've got a couple more estimates coming, but just got one from the company I like best, and just wanted a gut check on which route is likely to make the most sense for us.

• 15 SEER unit - single speed compressor + indoor blower unit + thermostat + install + 1 yr labor/10 yr parts warranty ~$5500
  
• 17 SEER unit - 2 stage compressor + indoor blower unit + thermostat + install + 1 yr labor/10 yr parts warranty ~$7500
  
• 18 SEER unit - variable speed compressor + indoor blower unit + thermostat + install + 2 yr labor/10 yr parts warranty (12 years for compressor) ~$8500
  

They could give us pricing on 14 SEER units on the low end, and 20 SEER on the high end as well, FWIW.

A few items for consideration:

• We are likely to be in the house for at least 10 years
  
• We have PV solar, so our normal electric bills are low/non-existent in spring-fall. Winter we are still generating of course, but typically not enough to cover the monthly bill (maybe 4-5 months). So perhaps a $100 electric bill in those months, but very low/no bills the other 7-8 months.
  
• Our appliances are entirely electric -- no gas/oil/etc.
  

So perhaps the question is two-fold:

1. How much efficiency is worth paying for in a heat pump? I'm sure there's a calculation that would give a clear answer. Is it a function of cost of electricity? or is it a function of the expected usable lifespan of the unit?
2. Our old heat pump is single speed. What do we know about reliability of 2 stage and variable speed compressors? Run away fast? Or embrace them as a natural advancement in compressor technology?

This is not a "done deal". Possible we will wait until spring, but wanted to at least get some numbers to see what the possibilities are. Looking for your experiences and recommendation. thanks!

[Ombligo]

i'd likely go with the 15 SEER. The higher ratings are most likely not going to pay you back. Over a period of 10 years, the savings between the 15 & 17 is only $800 (assuming a 3-ton unit, less if the units are smaller and a bit more if larger).

SEER Savings Calculator

[jh]

We replaced our old heat pump single speed unit with a two stage unit several years ago and are pleased with it. Recently installed a nest thermostat. The electric has gone down with the two stage unit.

[mikebw]

I would go with the 18. Not a huge performance difference energy-wise, but from what I have heard about variable speed compressors I think the more consistent comfort level will be worth it.

[DinerDave]

I learned a LONBG time ago, you get what you pay for. The low end will have a better cost of entry, but long term, I feel getting a higher capacity unit is best. I don't like to have something "to get you by".
A slightly more powerful unit wouldn't work as hard or strain under the occasional higher load.

Glad to hear you have solar. Lovin' mine!

Dave

[Bill in NC]

You'll want the variable speed blower fan (inside)...if that's included in the SEER 15 quote go for that.