Summer HVAC Tips: Staying Cool in Coastal Georgia

By Bryan Donaldson, Owner, On Time Air. 25+ years of HVAC experience in Savannah, GA.

Summer in Savannah isn’t really a heat problem. Plenty of places get hotter than we do. Phoenix hits 110 and people manage.

Our problem is moisture. Dew points in the low to mid 70s from June through September mean the air is carrying about as much water as it can hold, and that changes which advice actually works here. A fair amount of standard energy-saving guidance you’ll read online was written for dry climates and will make you less comfortable in coastal Georgia.

Here’s what works on the Georgia coast.

Thermostat Settings That Actually Work

Find your number between 75 and 78. The Department of Energy suggests 78 when you’re home. That’s a reasonable target, but it’s genuinely comfortable here only if your indoor humidity is under control. At 55 percent relative humidity, 78 feels fine. At 65 percent, 78 feels swampy and you’ll reach for the thermostat.

Which means the humidity is the lever, not the temperature.

Use setbacks, but keep them modest. Raising the setting 4 to 7 degrees while you’re out saves real money. But going much beyond that in our climate backfires. The house takes on moisture all day, and when you come home your system spends hours pulling it back out, running longer than it saved.

Four to six degrees is the sweet spot. Not fifteen.

Set the fan to AUTO, not ON. This is the single most common setting mistake I see, and it directly hurts you here. With the fan on ON, the blower runs continuously. Between cooling cycles it blows air across a wet evaporator coil, and that moisture evaporates right back into your house. You’re re-humidifying your own home.

AUTO. Always, in summer.

Don’t crank it to 65 to cool faster. Your system cools at exactly one rate. Setting it lower doesn’t speed anything up, it just overshoots and runs longer than needed.

Get the Humidity Right

Target 45 to 55 percent indoor relative humidity. Above 60 percent you get that clammy feeling, condensation on windows, and conditions that favor mold and dust mites.

A cheap hygrometer, fifteen dollars or so, tells you where you stand. Worth owning in this climate.

Things that help:

• Run bathroom exhaust fans during and for 20 minutes after every shower.
• Use the kitchen range hood when cooking, particularly anything boiling.
• Don’t oversize your AC. An oversized system short cycles and never runs long enough to dehumidify. This is the most common root cause of a home that’s cool and still clammy.
• Consider a whole-home dehumidifier if you’ve fought this for years. It works alongside the AC and handles moisture independent of temperature. More in our post on whole-home dehumidifiers.

Use Your Ceiling Fans Correctly

Ceiling fans should spin counterclockwise in summer, pushing air down. There’s a small switch on the motor housing.

A fan makes you feel about 4 degrees cooler through evaporation off your skin. That means you can raise the thermostat a few degrees and feel the same.

But fans cool people, not rooms. Turn them off when you leave. A fan running in an empty room is adding heat from the motor and costing you money for nothing.

Block the Sun Before It Gets In

Savannah’s summer sun through west-facing glass is a bigger load than most people realize. Late-afternoon sun is what drives your peak demand.

• Close blinds or curtains on west and south windows in the afternoon
• Cellular or honeycomb shades help noticeably
• Exterior shading helps more than interior, because it stops the heat before it’s inside
• If you’re replacing windows anyway, low-E coating makes a real difference here

Savannah’s live oaks are genuinely valuable for this. A shaded house runs measurably cooler.

Take Care of the Equipment

Change the filter monthly in summer. The system runs constantly, so filters load faster than the package suggests.

Keep the outdoor unit clear. Two feet on all sides. Cut back the azaleas and jasmine.

Rinse the condenser coil. Power off at the disconnect, garden hose, never a pressure washer.

Flush the condensate drain monthly. A cup of distilled white vinegar down the access port. In our humidity this prevents the single most common summer breakdown.

Don’t close vents in unused rooms. It feels logical and it’s wrong. Closing vents raises static pressure, reduces airflow across the coil, hurts efficiency, and can cause the coil to freeze.

Listen to your system. New noises, weaker airflow, longer run times, or a rising bill without a rate change are all early warnings. Small problems in May are cheap. The same problems in August are emergencies.

Reduce the Load Inside

• Cook outside when you can, or use the microwave, air fryer, or slow cooker instead of the oven
• Run the dishwasher and dryer at night when the load on your AC is lower
• Switch to LED bulbs if you haven’t; incandescents are small space heaters
• Unplug what you’re not using; electronics add up
• Seal the obvious leaks. Weatherstripping on doors, caulk around window frames, and sealing the attic hatch are cheap and effective. Attic air sealing is one of the highest-return improvements in a Savannah home.

Have a Storm Plan

We’re on the coast, so this belongs in a summer HVAC article.

Before a storm: if flooding is possible, shut the system off at the breaker. A surge when power returns can damage the compressor and control board. If you have time and the unit is in a flood-prone spot, know that a submerged condenser generally needs professional inspection before it runs again.

After power returns: wait 5 to 10 minutes before turning the system back on. Give the grid a moment to stabilize. Compressors also need time for pressures to equalize before restarting.

Consider a surge protector for the HVAC system. In a market with our storm frequency, it’s cheap insurance on an expensive compressor and control board.

After a flood: don’t run a system whose outdoor unit or ductwork has been submerged until it’s been inspected. Water in ductwork becomes a mold problem quickly in our humidity.

Get Service Before You Need It

I’ll say this plainly: the worst time to discover your AC has a problem is the first 95-degree Saturday, when every HVAC company in Chatham County is booked three days out.

A spring or early-summer service visit catches the weak capacitor, the low charge, the dirty coil, and the clogging drain while they’re still inexpensive. That’s the entire argument for maintenance plans, and it’s a good one.

Frequently Asked Questions

What temperature should I set my AC in Savannah summer? Between 75 and 78 when home, provided indoor humidity stays under 55 percent. Humidity control matters more than the number on the thermostat for how comfortable the house feels.

Should my AC fan be on AUTO or ON in summer? AUTO. With the fan on ON, the blower re-evaporates moisture off the wet coil back into your home between cooling cycles, which raises indoor humidity.

Does closing vents in unused rooms save money? No. It increases static pressure, reduces airflow across the evaporator coil, and can cause freeze-ups. Leave all supply vents open.

What indoor humidity should I target in coastal Georgia? 45 to 55 percent. Above 60 percent encourages mold and dust mites and makes the house feel clammy even at a low temperature.

Should I turn my AC completely off when I leave for the day? Not in a Savannah summer. The house absorbs moisture while the system is off, and recovering it costs more than the setback saved. A 4 to 6 degree setback is better than shutting it down.

Ready for the Season?

If you haven’t had your system looked at this year, now is a better time than July.

Serving Savannah, Pooler, Richmond Hill, Rincon, Tybee Island, Wilmington Island, and communities across Chatham, Effingham, and Bryan counties.

Call On Time Air at 912-210-4901 or request service online.

Related: HVAC maintenance plans, essential HVAC maintenance tips, and is my home energy efficient?