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Question DetailsAsked on 7/9/2014

difference between 13 seer and 16 seer hvac system?

The is the recommended square footage range for each seer?

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5 Answers

Voted Best Answer

I think maybe you are confusing SEER, which is an efficiency-related rating (higher SEER means more effective use of the electric power used to compress the gas), and TONS rating, which is a measure of the total cooling power of the system. (Tons used to mean how many tons per hour of ice was used in evaporative cooling building systems - a Refrigeration or Cooling Ton equals 12,000 Btu/Hour of energy exchange. A BTU, which is another antique measure but still used, is the energy needed to change the temperature of a pound of water one degree fahrenheit. Unfortunately, because of varying humidity and evaporation, this is not readily related to house air heating or cooling without a lot of assumptions and some computations.

Relating this to today's world - the Manuals BayAreaAc referred to account for all these energy conversions and determine an estimated cooling (or heating) requirement for your specific house. The type of construction, solar exposure, general climatic conditions such as average temperatures, humidity, and hottest and coldest normal ambient temperatures and desired inside temperture are all taken into account in the more sophisticated versions of the analysis, so there is no "standard", though a rough old rule of thumb was about 1 ton of cooling per 500SF of house. Obviously, this was a WAG only because it did not account for insulation, type of roofing, whether you live in Alaska or Miami, etc. The ACCA manuals do a very simplified form of evaluation to arrive at a "design", which generally will be adequate. OF course, highly precise calculations are not really needed because A/C units generally come in even ton ratings - so if you are at say 2.6 ton requirement you will be getting a 3-ton unit anyway.

SEER ratings are not a direct measure of efficiency, but the relative difference between ratings gives you good idea of the unit's relative efficency in using electricity - so a 16 SEER should be about 19% more efficient (so roughly comparable lower electricity bill) than a comparably sized 13 SEER unit. 13 SEER is the lowest efficiency currently allowed to be built for general use, 19 SEER is about the highest efficiency made by pretty much all manufacturers, and about 25 SEER is the highest rated though very pricey shelf-item units, though special construction custom units can reach about 30 SEER.

Note however, like any government sponsored rating, much of it is hooey when you get down to it - for instance, SEER ratings are figured based on 80 degree inside air temp and 82 degrees outside, when that is far from the normal case of mid to low seventies inside and high eighties or above outdoors. This makes the absolute SEER rating meaningless, but relative numbers still have meaning in comparing units.

Note these efficiency ratings are for conventional air conditoners and heat pumps working in ambient air conditions. Ground sourced Geothermal or lake/river exchange cooling units, though initially more expensive in most cases, can greatly exceed the air-exchange unit efficiencies because they are exchanging heat with cold natural water rather than with a high-temperature outside air, and instead of continually compressing a gas are just circulating cold water. I worked on one geothermal cooling project which had almost infinite efficiency, which of course makes no sense - but the only power was for sensors and a control valve as the water flow was single-pass under gravity flow, so no power was used to circulate the water.

Answered 6 years ago by LCD


SEER is Seasonal Electrical Energy Ratio. The higher the number the lower the cost to operate, like miles per gallon for your car. Size of the system/unit required is not related to SEER.

Sizing of a home AC system should be done by a Pro, using Manual J and Manual S from , the industry standard for sizing.

Please tell us more about your project, by using the Answer this Quetion feature.


Answered 6 years ago by BayAreaAC


Heating and cooling comfort area 1500 sq ft single story house in Ontario California. Current 40+ year old Day and Night split forced air furnace (located in a closet) and central air conditioner (rooftop) - gas/electric. Very minimal insulation, single payne windows, thin wood doors and original hardwood floors (wishlist windows/doors/flooring). UNIT HAS STOPPED WORKING--BEST SONA EVER, lol--. Would like to replace HVAC system and need clarity on how to choose the correct system. From research it appears that a 3-ton, 13 Seer Trane is the recommended unit. Air conditioner - roof/top versus ground level; furnace remain in closet. Just as important price range.

Answered 6 years ago by Guest_90835841


I would check first why the A/C is on the roof - required in your area by code or subdivision covenant for appearance and noise control, maybe. That would certainly impact your decision.

Assuming you have forced air furnace like most houses in SoCal, then moving the units without reason serves little purpose. Your rooftop unit is possibly less efficient than a ground-mounted unit in your area since the ambient temperature on the roof is much higher and you are not in an area with significant prevailing winds (unless up in the hillside/Sierra Madres area) except for the hot Santa Anas (which provide no cooling), but if there is a lot of cost in ducting changes to swap to a ground-mounted unit it might not pay off.

Certainly, in your environment you are looking at a small furnace which is not used too much (although reaching heating temperature outside almost 12 months a year), so spending a lot of money on efficiency would not save you much there, especially if natural gas fired as I assume - so I would just go with a good brandname 80% efficiency unit for that. The A/C is where you should be concentrating your research regarding the cost-benefits of higher efficiency units, because you have about 8 A/C months a year, and three well into the 90's for average daytime high - not to mention the smog which makes people keep their windows closed a lot of the time, hence more air conditioning demand.

SCE, TheGasCompany, and the US Dept of Energy EnergyStar program all have good website info on typical cost-benefits of more efficient units, and the utilities have info on the cost of your power and gas on your bill so you can use actual energy costs in figuring your expected cost. Bear in mind to use only the energy charge parts, not including the fixed flat monthly service rate or fixed government charges which does not change with usage. May be several types of charges based on energy usage, and some government fees or taxes related to that too - if you can not figure out which to use, call the energy conservation office or billings office at your utility and they should be able to explain it to you - as can the webpages explaining your bill (also sometimes on the back). Haven't used those utilties for quite awhile so don't know what they have on their bills now.

Like prior comment said, contact several HVAC contractors with good reviews and ratings, then talk to them about brand and configuration possibilities and have them take measurements and do the required Manual calculations to size your system but tellthem NOT to prepare a bid right off, then after talking to about 3 decide what efficiency and type of unit you want and brands you will accept, THEN call all back and have them all bid on the same general system requirements (furnace Btu and A/C tons and SEER rating, etc) (though they will likely bid different brands).

IF you are planning on staying in this house for a long time or see little chance of a move in the future so this replacement is a long-term investment for you, I would consider a higher efficiency unit like SEER 16-18 range for your area. You are in a serious A/C environment much of the year and SoCalEdison rates certainly are not going to be going down, and with San Onofre being abandoned and Diablo Canyon cutting back power, Hoover and Glen Canyon Dams producing less power due to the water shortages, and the Four Corners area coal plants being pinched by the new coal air pollution regulations, your rates will be increasing even more - quite likely dramatically in the next few years. I know in our area we have had 40% electricity and 48% gas consumption rate increases this year already and over 100% total increase in the past 3 years or so, and more coming.

Answered 6 years ago by LCD


3 seer :-)

Answered 5 years ago by DonChepe


Each SEER point up you go is close to 8% saving each year in operating cost per year youare still in the home, for the life of the equipment. Square footage does not play into savings.


Answered 5 years ago by BayAreaAC

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