# SEER 10 Vs SEER 20, payback calculations

Solar Expert Posts: 834 ✭✭
I think my exsisting Central AC compressor/air handler is SEER 10. I'm thinking of upgrading to a SEER 20. does that mean a new unit is twice as effcient? So my electrical bills will be half of what they are?

• Solar Expert Posts: 834 ✭✭
Re: SEER 10 Vs SEER 20, payback calculations

http://en.wikipedia.org/wiki/Seasonal_energy_efficiency_ratio
i guess according to the above web page I am right. Never knew AC has gotten this effcient.
• Solar Expert Posts: 3,123 ✭✭✭✭
Re: SEER 10 Vs SEER 20, payback calculations
http://en.wikipedia.org/wiki/Seasonal_energy_efficiency_ratio
i guess according to the above web page I am right. Never knew AC has gotten this effcient.

That is what it means alright. Add some simple additional steps like keeping the condensor unit out of direct sun, minimizing sun load by passive solar design and you are looking at some serious savings.
And, as the wikipedia article stated, SEER of 27 is available now and the sort of inverter and variable speed technology found in good mini-split systems holds the promise of even better performance in the future.
But it does not all multiply out to an ideal solution. The more you reduce the amount of A/C you use in the first place, the less you save by increasing the SEER of your A/C. And the better your SEER, the less you save by reducing the amount of A/C you use. Your total savings can never be more than the amount you are currently paying! (Although you may end up more comfortable by using more A/C.)
Similar improvements in Coefficient Of Performance (COP), the equivalent figure of merit for heat pumps, have made use of heat pumps (both air source and ground source) more attractive compared even to use of propane for heating.

These forums keep mentioning that resistance heating is a wasteful use of PV, especially compared to solar thermal. But if the energy from PV goes into a heat pump instead, the difference is not nearly as striking.
SMA SB 3000, old BP panels.
• Solar Expert Posts: 223 ✭✭✭
Re: SEER 10 Vs SEER 20, payback calculations
I think my exsisting Central AC compressor/air handler is SEER 10. I'm thinking of upgrading to a SEER 20. does that mean a new unit is twice as effcient? So my electrical bills will be half of what they are?

Probably not.
You will pay a premium for that 20 SEER unit. Unless you live in a hell like environment where the A/C runs 24/7 it will take 20+ yrs to make up the difference in cost from your utility savings the make up the difference in install costs. Repairs are quite a bit more costly also on the high SEER units than on the 13 SEER if you have a problem.
If you live in a warm climate 15 SEER is the break even system where the upgrade costs vs energy savings vs system life span makes economical sense.
• Solar Expert Posts: 1,164 ✭✭
Re: SEER 10 Vs SEER 20, payback calculations

A couple years ago I upgraded from an old SEER 9.8 to a SEER 17, and power costs dropped around 15% or so, roughly. But the main payback was much better cooling throughout the house. And because it is more efficient I also tend to run it about 1 degree lower than the old unit, which had trouble even dropping the inside temp below 80 on very hot days. So because I dropped the set temp a degree or two, hard to really compare how much I saved.
• Solar Expert Posts: 2,367 ✭✭✭✭
Re: SEER 10 Vs SEER 20, payback calculations
LucMan wrote: »
Probably not.
You will pay a premium for that 20 SEER unit. Unless you live in a hell like environment where the A/C runs 24/7 it will take 20+ yrs to make up the difference in cost from your utility savings the make up the difference in install costs. Repairs are quite a bit more costly also on the high SEER units than on the 13 SEER if you have a problem.
If you live in a warm climate 15 SEER is the break even system where the upgrade costs vs energy savings vs system life span makes economical sense.

Agreed my AC guy showed me a chart where in AZ a 17 seer is the sweet spot for payback. If you are running off solar however more efficient is less dollars spent on generation so that could play in as well.
• Solar Expert Posts: 223 ✭✭✭
Re: SEER 10 Vs SEER 20, payback calculations

The higher SEER units were designed for people in Arizona type climates, mostly sensible cooling, not much latent cooling required. Here on the east coast those SEER ratings are not that accurate as the total cfm through the air handler has to be lowered to accommodate for more latent cooling. When they first came out with the R-410 high SEER units there was a real problem with dehumidification in humid environments. Evaporator coils went from having 3-4 row coils down to single row coils, not conducive to removing moisture from the air. Now they match a 3 ton condenser to a 5 ton coil and an ECM motor to get a 15 SEER unit. They work well for our 3 month cooling season but I don't think they really are operating at 15 SEER levels as the airflow is low.