Climate, existing ductwork, and fuel access decide this more than any spec sheet does.
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HVAC systems and efficiency
Choosing between system types has more to do with climate and existing equipment than with any single number on a spec sheet: this section explains the actual mechanics behind the comparison.
Comparing systems on how they work, not what they cost
This section deliberately stays away from prices and current tax incentives, both of which change constantly and vary by region. A number printed here would be out of date within a year. What it does cover is how different systems actually function, so the comparison holds up regardless of what things cost this particular year.
Systems guides
A seasonal efficiency ratio, not a comfort score: what SEER2 changed and what a higher number buys you.
Age, refrigerant type, which part failed, and the efficiency gap. The four things that actually decide it.
One central furnace or air conditioner, several thermostats: dampers and a control panel decide where the air actually goes.
Fifteen to twenty years is the usual range, but sizing, filters, and maintenance decide which side of it you land on.
SEER2, HSPF2 and COP each answer a different question, and outdoor temperature changes all of them.
A thermostat, a heating or cooling source, a blower and a set of ducts: one loop behind most symptoms.
Insulation comes first, and in a closed space the fuel you burn matters more than the heater you buy.
The seasonal heating rating for heat pumps, how it differs from SEER2 and COP, and what it leaves out.
Climate, insulation, windows and ducts set the size, and a load calculation beats a square footage chart.
Heat loss decides furnace size, and an oversized unit short cycles.
A ton is 12,000 BTU per hour of cooling, and the right number comes from your house, not a chart.
How SEER2 differs from SEER, what it measures and what it leaves out.
Cut the heat coming in first. Then match the cooling method to how you use the space, and keep fuel and fumes out of the picture.
What changed between the old and new AC refrigerant, why R-22 is hard to find, and what that means for repair or replacement.
The main parts of a home HVAC system grouped by job, where they live, and which ones are safe for you to check.
One outdoor cabinet or a split indoor and outdoor setup: how they differ and when each one makes sense.
The hot-day efficiency number for air conditioners, how it differs from SEER2, and when it is the one to use.
The percentage of a furnace's fuel that becomes heat, what it leaves out, and how to use it when comparing models.
The calculation that decides how much heating and cooling your house needs, and why rules of thumb fail.
A simple way to work out your own air conditioner's use, and what makes it draw more.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- ENERGY STAR. Energy Savings at Home: Heating & Cooling
- US EPA. Section 608 of the Clean Air Act