The daily electricity cost of an air conditioner = the kWh used in a day × the tier rate your billing period falls in, and the kWh cannot simply be "rated power × hours switched on", especially for an inverter model (變頻機). Take a 4.1 kW model on the label page of the Energy Administration, Ministry of Economic Affairs as an example: at rated cooling capacity its power consumption is 1.070 kW, and at rated intermediate cooling capacity (2.000 kW) it is 0.330 kW. Running 8 hours, multiplying by 1.070 kW gives 8.56 kWh and multiplying by 0.330 kW gives 2.64 kWh, a difference of more than three times. Actual consumption mostly falls somewhere between the two, but this is not a conclusion stated by the source; running below the intermediate capacity would be lower still, and under a very high load it could be higher. Below, the label fields published by the Energy Administration are used to write the calculation, and the kWh ranges for sleeping 8 hours and for a full 24 hours, as formulas you can plug your own numbers into; the bill is then found by applying Taipower's progressive tiers.
For the basic way to convert appliance wattage to kWh, see How many kWh does an appliance use in an hour? Converting watts to kWh and electricity cost; this article is only about air conditioners. The relationship between air conditioner tonnage and power use is outside the scope of this article.
The basic formula for air conditioner electricity cost
Electricity cost = kWh × unit rate. kWh = power (kW) × time (hours). The problem is which number to use for "power": an air conditioner is not an appliance with fixed power, and the rated power consumption on the nameplate or label page is the power when the machine runs under rated conditions, not its average power over a whole day.
| Estimation method | Calculation | Applicability and limits |
|---|
| Rated-power method | kWh = rated power consumption (kW) × hours switched on | Assumes the machine runs at rated conditions all the time; the most direct method, but often too high for inverter models |
| Range method (for models with intermediate-capacity data) | Reference range of kWh: from "power consumption at intermediate capacity × hours" to "rated power consumption × hours" | Usable only for models whose Energy Administration label page has a rated intermediate cooling capacity filled in; actual consumption depends on room temperature, settings and sunshine, and is not guaranteed to fall within the range |
| CSPF method | kWh = cooling needed over that period (kWh) ÷ CSPF | CSPF has the unit kWh/kWh and is the average efficiency over a whole cooling season; you need to know the amount of cooling yourself, which ordinary households find hard to estimate, so the labelled annual consumption is usually used instead |
CSPF is the cooling seasonal performance factor (冷氣季節性能因數). The Energy Administration's energy magazine explains that, based on Taiwan's climate conditions, it analyzes an air conditioner's full-year cooling demand and operating electricity consumption to work out the operating efficiency over a whole cooling season, replacing the EER that used to be calculated under fixed conditions. The notice requires measured values to be tested under CNS 3615 and to be at least 95% of the labelled value on the product.
The actual fields on the Energy Administration label page
The table below gives four entries from approved-product pages of the Energy Administration's energy efficiency grading label management system (能源效率分級標示管理系統), opened on 2026-11-07, product category ductless air conditioners, 2025 standard (無風管空氣調節機(114年基準)); only model numbers and figures are taken, and this is not a recommendation. The label pages do not say fixed-speed or inverter; a model whose "rated intermediate cooling capacity" field has a value has data for running at a lower cooling capacity, while that field is blank for CU-41NH and MAS-41MG. The CSPF of CU-41NH, 3.78, happens to equal the minimum benchmark of 3.78 for that capacity tier.
| Model | Unit configuration | Rated cooling capacity | Rated power consumption | Intermediate capacity / power consumption | CSPF | Grade | Annual consumption (label page) |
|---|
| CU-41NH | one-to-one split type (一對一分離式) | 4.1 kW | 1.137 kW | field blank | 3.78 | Grade 5 | 1,290 kWh/year |
| 38QCE041D8SA | one-to-one split type | 4.1 kW | 1.070 kW | 2.000 kW / 0.330 kW | 6.12 | Grade 1 | 796 kWh/year |
| CU-UJ28BHA2 | one-to-one split type | 2.8 kW | 0.570 kW | 1.41 kW / 0.218 kW | 6.86 | Grade 1 | 485 kWh/year |
| MAS-41MG | single-unit type (單體式) | 4.1 kW | 1.133 kW | field blank | 3.79 | Grade 4 | 1,286 kWh/year |
Three things can be seen from this table. First, the rated power consumption of the first two models differs by only 0.067 kW (1.137 versus 1.070), but the annual consumption is 1,290 versus 796 kWh, a difference of about 62%; looking only at rated power would badly underestimate the advantage of a high-CSPF model. Second, for models with intermediate-capacity data, the power consumption at intermediate capacity is only about one third of the rated figure (0.330 versus 1.070; 0.218 versus 0.570, a little over one third). Third, plugging into "rated cooling capacity × hours ÷ CSPF", the hours for all four entries come to about 1,189 (4.1 × 1,189 ÷ 3.78 ≈ 1,290; 4.1 × 1,189 ÷ 6.12 ≈ 797; 2.8 × 1,189 ÷ 6.86 ≈ 485; 4.1 × 1,189 ÷ 3.79 ≈ 1,286). This is a result this article back-derived from the Energy Administration's label data, not an explanation published by the Energy Administration; that is, the labelled annual consumption corresponds to an amount of cooling of "rated cooling capacity × 1,189 hours", divided by CSPF, and is not the consumption of running 24 hours every day.
How progressive pricing is applied, and how current the rates are
Residential electricity uses progressive pricing: the more you use, the higher the per-kWh rate for the portion above each threshold. Summer months run from June 1 to September 30 each year, after which the lower non-summer rate resumes (as explained in a 2017 news item from the Executive Yuan (行政院); follow Taipower's current announcements). The billing period on an electricity bill is 2 months, and Taipower's estimation page also reminds you to divide the kWh on the bill by 2 to get the monthly kWh. To convert the extra kWh from air conditioning into cost, the steps are:
- Work out the extra kWh per month from the air conditioner (the table in the next section).
- Add it to your original monthly kWh to get the new total monthly kWh.
- Following Taipower's rate table, multiply each tier by its unit rate to get the new electricity cost.
- The new cost minus the original cost is the extra electricity cost from the air conditioner.
For each tier's unit rate, follow Taipower's latest rate table or your electricity bill; this article lists no unit rates.
How current this is: the "approved rates" page in the electricity price information disclosure section (電價資訊揭露專區) of the Energy Administration says that the unit rates applicable to each type of electricity use were approved by the Ministry of Economic Affairs on September 26, 2025 and take effect from October 1, 2025; the review committee meeting resolved on March 27, 2026 that rates would not be adjusted, and the review committee meeting on September 18 resolved to postpone the decision on this rate adjustment, leaving it to be discussed together at the 3rd review committee meeting in December. So the unit rates are as announced on 2026-11-07 and may change after the end of the year. For an overall look at water and electricity prices in Taipei and New Taipei, see the article on water and electricity prices in Taipei and New Taipei; to find out whether time-of-use rates suit you, see Is Taipower time-of-use pricing suitable for ordinary households.
kWh ranges for sleeping 8 hours and for a full 24 hours
Assumptions: the model is 38QCE041D8SA above; the air conditioner runs 8 hours a day (sleeping) or 24 hours a day (all day) for 30 days in a row; power uses only two label fields, power consumption at intermediate capacity of 0.330 kW and rated power consumption of 1.070 kW, as the two ends of the reference range.
| Hours on per day | Power used | kWh per day | kWh over 30 days |
|---|
| 8 hours | 0.330 kW (intermediate capacity) | 2.64 | 79.2 |
| 8 hours | 1.070 kW (rated) | 8.56 | 256.8 |
| 24 hours | 0.330 kW (intermediate capacity) | 7.92 | 237.6 |
| 24 hours | 1.070 kW (rated) | 25.68 | 770.4 |
How to read this table: the kWh for sleeping 8 hours and for a full 24 hours differ by exactly three times, but the electricity cost differs by more, because the added kWh fall into higher tiers and the per-kWh rate is progressive; the higher your original kWh, the more easily the added kWh land in the more expensive tiers. This table is just two label fields multiplied by hours, and real use is not at fixed power, so it is meant to show you the order of magnitude, not to predict. For comparison, spreading the labelled annual consumption over 365 days gives about 2.18 kWh a day for 38QCE041D8SA (796 ÷ 365) and about 3.53 kWh a day for CU-41NH (1,290 ÷ 365), but the labelled annual consumption is an estimate under label conditions and does not mean a daily average. Plug in your own original kWh and model figures, or use the appliance electricity cost calculator.
How to calculate for a window-type air conditioner
The Energy Administration label field is "single-unit type" (單體式); this article infers that it corresponds to window-type units, and no official word-for-word correspondence was found. The rules for window (wall) type and box type air conditioners were merged into the same ductless air conditioner standard by a combined notice dated August 11, 2015 (taking effect from 2016), and MAS-41MG in the table is an example of a single-unit type label. The calculation is the same: estimate with the rated power consumption on the nameplate and the hours switched on, and cross-check with CSPF and the labelled annual consumption. For choosing tonnage, see How to choose air conditioner tonnage and the air conditioner tonnage calculator.
Power-saving practices that have a source
- Choose a model with a high CSPF: the Energy Administration's "36 power-saving tips" (省電36計) says that the higher the CSPF, the more energy-saving the air conditioner, and that generally each 0.1 increase in CSPF saves 2-3% of the air conditioner's electricity. This is a rough estimate by the Energy Administration, not a guarantee for every machine.
- Temperature setting: the Energy Administration's 36 tips say the air conditioner temperature is best set in the range of 26-28℃; the buying guide of the Bureau of Standards, Metrology and Inspection (BSMI), Ministry of Economic Affairs also says the recommended setting is 26 to 28℃, used together with an electric fan or circulating fan.
- Cleaning the filter: the Energy Administration recommends cleaning the air filter once every two weeks; BSMI reminds that dust building up on the filter lowers the incoming airflow and makes the air conditioner use more electricity.
- Shading: for windows facing east or west, the Energy Administration recommends installing blinds or curtains to reduce solar radiant heat entering the room and so lower the air-conditioning load and electricity use.
FAQ
About how much does it cost to run the air conditioner for a day?
There is no single answer. For the same 4.1 kW model, with the label fields plugged in as in this article, sleeping 8 hours uses about 2.64 to 8.56 kWh a day and running all day uses about 7.92 to 25.68 kWh a day; multiplying by the tier rate your billing period falls in gives the cost. The gap comes from the actual power and from how many kWh your home already uses. Please plug your own kWh, model and hours into the formulas above.
Is an inverter air conditioner always more energy-saving than a fixed-speed one?
The Energy Administration label page has no "fixed-speed" or "inverter" field, so this article draws no conclusion using these two terms. Of two models with the same 4.1 kW, 38QCE041D8SA, which has intermediate-capacity data, has a labelled annual consumption of 796 kWh/year (Grade 1), while CU-41NH, whose intermediate-capacity field is blank, has 1,290 kWh/year (Grade 5). Please go by the CSPF and annual consumption of the model you want to buy.
Is running the air conditioner all day more energy-saving than switching it on and off?
This article found no official comparison by the Energy Administration or BSMI of "keeping it on" versus "switching it on and off", so it draws no conclusion. You can use this article's formulas, plug in your actual hours and the model's power, calculate each way of running once, and then compare.
Why are electricity bills higher in summer months?
Taipower applies summer rates each year from June 1 to September 30, and from October 1 returns to the lower non-summer rate (as explained in a 2017 Executive Yuan news item); in addition, air conditioning raises the kWh into higher tiers, and because the per-kWh rate in progressive pricing gets higher the further up you go, the summer bill increases by more than the kWh do.
Sources
- Energy Administration, Ministry of Economic Affairs, energy efficiency grading label management system: model CU-41NH (verified 2026-11-07) (in Chinese): rated cooling capacity, power consumption, CSPF, grade, annual consumption
- Same system: model 38QCE041D8SA (verified 2026-11-07) (in Chinese): rated and intermediate-capacity power consumption, CSPF, annual consumption
- Same system: model CU-UJ28BHA2 (verified 2026-11-07) (in Chinese): rated and intermediate-capacity power consumption, CSPF, annual consumption
- Same system: model MAS-41MG (verified 2026-11-07) (in Chinese): single-unit type (單體式), rated power consumption 1.133 kW, CSPF 3.79, annual consumption
- Energy Administration: notice on the permitted energy consumption benchmark and the energy efficiency grading label items, methods and inspection of ductless air conditioners (verified 2026-11-07) (in Chinese): CSPF tested under CNS 3615, measured values must be at least 95% of the labelled value
- Energy Administration energy magazine: a more advanced air conditioner energy-saving standard, CSPF (verified 2026-11-07) (in Chinese): the meaning of CSPF and the explanation of its replacing EER (article of 2017-05-24)
- Energy Administration, Ministry of Economic Affairs: 36 power-saving tips (省電36計) (verified 2026-11-07) (in Chinese): each 0.1 increase in CSPF saves about 2 to 3%, 26 to 28℃, filter, shading (page content updated 2025-07-10)
- Bureau of Standards, Metrology and Inspection (BSMI), Ministry of Economic Affairs: notes on buying and using air conditioners (verified 2026-11-07) (in Chinese): 26 to 28℃ with an electric fan, filter cleaning, electrical specification labels (published 2025-06-06)
- Energy Administration electricity price and rate review information disclosure section: approved rates (verified 2026-11-07) (in Chinese): unit rates take effect from October 1, 2025; the news releases in the same section list the resolutions of 2026-03-27 and 2026-09-18
- Taiwan Power Company (Taipower) time-of-use rate estimation for metered lighting customers (verified 2026-11-07) (in Chinese): summer months are June to September, the billing period on an electricity bill is 2 months
- Executive Yuan website: summer rates start on June 1 as usual (verified 2026-11-07) (in Chinese): the summer rate period is June 1 to September 30, and from October 1 the lower non-summer rate resumes (news of 2017-05-24; follow Taipower's current announcements)
