Air Conditioning in the Caribbean: What It Really Costs

An air conditioner can easily become one of the most expensive appliances in a Caribbean home. The problem is that many owners know the size of the unit — “9,000 BTU”, “12,000 BTU”, “18,000 BTU” — but do not know how many kilowatt-hours it actually consumes or what that means on the electricity bill. This page turns the label on the machine into dollars, and shows when insulation, maintenance or replacing an old unit is the better investment.

What one air conditioner can cost in a year

Grenlec's published August 2026 domestic components add up to approximately EC$1.07 per kWh before customer-specific taxes, levies or temporary relief measures. At the fixed EC dollar exchange rate, that is about US$0.40 per kWh. A unit averaging 1.0 kW for 10 hours per day therefore costs roughly EC$322, or about US$119, in electricity every 30 days. Run two similar units and the cooling cost alone can exceed US$2,800 per year.

Calculator 1: what is your A/C costing?

Where do you find the kW number?

Look at the data plate or technical sheet for terms such as rated input, cooling input, power input or watts. Divide watts by 1,000 to get kW. For example, 950 W = 0.95 kW. With an inverter unit, the actual input changes continuously, so the label is not the same as long-term average consumption. The most reliable figure is measured kWh over several normal days, divided by the hours the unit operated.

A quick way to compare two 12,000 BTU units

For units with the same cooling capacity, you can make a simple first comparison from rated input. A 12,000 BTU/h unit drawing 1,200 W has an EER of about 10. A unit producing the same 12,000 BTU/h while drawing 800 W has an EER of about 15. At that rating point, the second machine uses one-third less electrical power. Seasonal real-world savings will differ because inverter speed, room load and humidity change constantly.

Why an inverter unit can save money

A traditional fixed-speed compressor is largely either on or off. Once the room approaches the desired temperature it cycles repeatedly. A variable-speed or inverter compressor can reduce its output and continue running at a lower level. ENERGY STAR describes variable-speed technology as significantly more efficient because the unit can continuously match capacity to the room instead of repeatedly operating at maximum output.

That does not mean every inverter saves the same percentage. A modern inverter in a well-insulated bedroom may spend much of the night at low power and perform extremely well. The same unit in an uninsulated room with a sun-baked roof may remain near high output because the building keeps feeding heat into the room.

Calculator 2: should you replace the old unit?

If you can estimate the average kW of your present unit and the expected average kW of a replacement, this calculator shows the simple payback. It is deliberately based on electricity rather than marketing claims.

A Grenada example

Using roughly US$0.40/kWh as a current Grenada planning figure, an old unit averaging 1.2 kW for 10 hours every day uses about 4,380 kWh per year and costs roughly US$1,752. If a properly sized replacement averaged 0.8 kW under the same usage pattern, the difference would be about 1,460 kWh or US$584 per year. If the installed replacement cost US$900, the simple payback would be about 1.5 years. The actual result must be checked with measured consumption and a real quotation, but this example shows why efficiency matters much more on an island with expensive electricity than it may in a low-cost electricity market.

Do not buy a bigger unit “to be safe”

Oversizing is a common mistake in hot climates. A larger machine cools the air quickly, but a fixed-speed unit may then switch off before it has removed enough moisture. DOE and ENERGY STAR both warn that oversized air conditioners can waste energy and provide poorer humidity control. In a Caribbean bedroom, that can mean a room that is cold but still feels damp.

Room area alone is not enough for final sizing. Roof insulation, window area, orientation, ceiling height, occupancy, appliances, air leakage and humidity all affect the real cooling load. A competent installer should size the unit from the room and building, not simply replace a 18,000 BTU unit with another 18,000 BTU unit because that is what was there before.

Humidity: the part many people miss

Cooling and drying are related but not identical. EPA recommends controlling indoor humidity because high humidity encourages mold. In a tropical home, keeping relative humidity below about 60% is an important practical target; lower levels may be desirable where achievable without excessive cooling.

If the room reaches a very low temperature but still feels damp, lowering the thermostat further is usually a poor solution. First check whether the machine is oversized, whether doors and windows are leaking, whether the evaporator is clean, whether condensate is draining correctly and whether the house is bringing in large amounts of humid outdoor air.

Five checks before buying a new A/C

1. Clean the filter. ENERGY STAR advises checking filters monthly. Restricted airflow makes the system work harder and can lead to additional maintenance problems.
2. Clean the outdoor and indoor heat-exchange surfaces when required. Salt, dust and biological growth can reduce heat transfer. Follow the manufacturer's service instructions.
3. Check condensate drainage. A blocked drain is a moisture problem and can become a mold problem.
4. Measure the electricity. Record several normal days before deciding that the machine itself is the problem.
5. Look at the building. A hot uninsulated roof can cost more over time than the difference between two air-conditioner models.

Coastal houses need another check: corrosion

An outdoor condenser near the sea can deteriorate far faster than the same machine inland. Salt deposits attack coils, fins, cabinets, electrical terminals and fasteners. When buying a replacement, ask whether the outdoor unit is intended for coastal exposure and what the manufacturer requires for cleaning and corrosion protection. Do not spray unknown coatings onto heat exchanger surfaces; some products reduce heat transfer or damage the coil.

Where should the outdoor unit go?

It needs unrestricted airflow and access for maintenance. Keeping it away from concentrated roof runoff, flooding and the strongest salt spray is useful. Shade can reduce direct solar heating, but never build a tight box around the condenser. Any shade structure must leave the manufacturer's required clearances and must itself be secured for hurricane winds.

When insulation is the better purchase

Questions to ask before buying a new unit

• What is the cooling capacity in BTU/h?
• What is the rated electrical input in watts?
• What efficiency rating is used, and can it be compared directly with the other model?
• Is the compressor variable-speed / inverter?
• What is the minimum and maximum operating input?
• Is the outdoor unit suitable for coastal or salt-air exposure?
• Who supplies parts and service on this island?
• What is the warranty on the compressor and on the complete unit?
• How was the required capacity calculated for this room?

The three pages work together

If your main problem is heat entering through the building, start with the DIY Tropical House Insulation Guide. If you have already reduced unnecessary consumption and want to generate the remaining electricity yourself, use the Caribbean Solar and Battery Guide. The cheapest kilowatt-hour is often the one your house no longer needs.