Inverter aircon payback calculator

How to use this inverter aircon payback calculator

Enter the annual kWh from each model's Energy Label, the price difference from your own quotes, the hours you run the aircon each day and the tariff on your bill. Put the model that uses more electricity in A and the more efficient model in B. Both models should have the same cooling capacity, which the label shows in kW.

The calculator does not check capacity, so match it yourself. If you have not sized the room yet, work out the capacity you need with the aircon BTU calculator first, then compare two models of that size.

Where to find the numbers

The National Environment Agency (NEA) explains on its Energy Label page that the label shows each model's annual energy consumption in kWh and rates its efficiency from 1 tick (Low) to 5 ticks (Excellent). For aircons, the kWh assumes 8 hours of daily use plus 16 hours standby. The label also prints an annual energy cost, but that cost uses fixed assumptions NEA states on the label, not your tariff. For split and multi-split aircons, the label is fixed to the outdoor unit and shows the outdoor unit's model number, along with the cooling capacity in kW, rounded to two decimal places.

If you are choosing between a 5-tick or 3-tick aircon, the kWh figures on the two labels are what you enter.

The price difference comes from your own quotes for the two models. Ask whether both quotes cover the same items.

The tariff box starts at the label's own assumption, so replace it with the rate on your bill. SP Group's tariff page explains that tariffs are revised every quarter to reflect the actual cost of electricity, so check the current rate there.

How the calculation works (method and sources)

The calculator follows two steps:

• Saving a year = (kWh A - kWh B) x (hours a day / 8) x tariff in cents / 100
• Payback in years = price difference / saving a year

Dividing by 100 turns cents into dollars. The saving shows to 2 decimal places and the payback to 1, and both are repeated at half and one and a half times your hours in a small 3-row table.

The hours step is a simplification. The label kWh assumes 8 hours a day and already includes the label's standby assumption, and the tool scales it in proportion to your hours. Real use is not exactly proportional: your settings, the room and the weather all change how hard the aircon works. Read the result as a guide, not an exact figure.

NEA's tips on buying energy-efficient appliances suggest looking at life cycle cost, not just the purchase price. Life cycle cost is the purchase price plus the annual energy cost times the lifespan in years. NEA also says appliances with more ticks on the Energy Label are generally more energy efficient. This calculator covers the energy part of that sum.

If your question is "is inverter aircon worth it", the payback years are the part you can work out. How long the unit lasts is the other part, and no official source gives that figure.

Reading the result

A short payback means the yearly saving covers the price gap sooner. A long payback means more years of lower bills before the extra price is covered.

If model B does not use fewer kWh than model A on the label, there is no saving to count. The tool then says: "Model B does not use less electricity on the label, so there is no payback." Check that you entered the more efficient model as B.

Look across the 3-row table as well. If the payback changes a lot between half and one and a half times your hours, your hours matter, so estimate them carefully.

The tool cannot tell you how long either aircon will last, because no official source gives a lifespan. Set the payback years against how long you expect to keep the unit.

To compare the two types in more detail, see inverter or non-inverter aircon. To estimate what a single model costs to run, use the aircon running cost calculator.

Limits of this estimate

The calculator compares label figures, not measured use. Real use depends on your settings, the room and the weather, so your bills may not change by exactly the amount shown. It does not include installation, servicing, repairs or lifespan, because no official source gives aircon lifespans. Both models should have the same cooling capacity, and the tool does not check this.

Installation cost depends on the job, and it sits outside this sum. For more on it, see aircon installation cost in HDB flats. If you are deciding whether to keep an older unit going rather than buy either model, read repair or replace an old aircon.

Questions