Energy Audit with a portable power meter

       How to save energy at home? Check out this page for my home appliance's electricity consumption.

Let us begin energy/environment conservation for our planet by first understanding how and where we have wasted our energy.

Edited by Lim Siong Boon, last dated 12-Dec-2011.

email:    contact->email_siongboon  


Topic Discussion Overview

  1. How much is the electricity tariff rate costing us?
  2. Power Meter
  3. Home Appliances Power Consumption
  4. Lightings



1. How much is the electricity tariff rate costing us?

The Singapore electricity tariff rate has been rising steadily 18.03 (as of Apr 2009) to 27.28 (as of Jul 2011) ; A wopping 151% increase in tariff rate. How does this tariff rate relates to the electrical appliances that we are using at home?

The following example show you how to compute the cost of our electricity cost.


Assuming a device consuming 10W 24hr per day for one whole month.

Total energy consumption in a single day = 10W x 24hr = 240 Whr

Total energy consumption in a month = 240Whr x 31days = 7440 Whr = 7.44kWh

The bill for 7.44kWh of electricity consumption will be = 7.44kWh x $0.2728/kWh = $2.029632


This means that the appliance consuming 10W will cost me $2/mth.

Appliance consuming 20W will cost me $4/mth.

Appliance consuming 100W will cost me $20/mth.

If the tariff rate go up, the cost of electricity per watt will relatively increase as well.


What can I do to reduce my electricity bills, at the same time conserve our global energy resource?

First I have to understand my energy consumption in my own house, by doing a simple energy audit.

Being energy conscious will be the very first step to start save energy.

The energy audit of my home shown on this page will be based on the latest tariff rate of 27.28 (as of Jul 2011).




Our electricity tariff in Singapore since 2009.

Energy cost: S$0.1803/kWh as on 1st Apr 2009

Energy cost: S$0.1928/kWh as on 1st Oct 2009

Energy cost: S$0.2169/kWh as on 1st Oct 2009

Energy cost: S$0.2287/kWh as on 1st Jan 2010

Energy cost: S$0.2356/kWh as on 1st Apr 2010

Energy cost: S$0.2413/kWh as on 1st Jul 2010

Energy cost: S$0.2334/kWh as on 1st Oct 2010

Energy cost: S$0.2410/kWh as on 1st Jan 2011

Energy cost: S$0.2558/kWh as on 1st Apr 2011

Energy cost: S$0.2728/kWh as on 1st July 2011

Energy cost: S$0.2698/kWh as on 1st Oct 2011

Energy cost: S$0.2759/kWh as on 1st Jan 2012






- (more tips to save energy)

- Singapore electricity tariff rate Jun 2011

- Singapore electricity tariff rate Jan 2012



Calculator for computing Appliance's Electricity Cost
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2. Power Meter

The beginning of this page starts with my handy portable power meter. It will be the most important instrument to help me measure the power consumption of the everyday appliances in my house. It was a coincidence that I brought my power meter. I had always like to have such a power meter to measure power consumption for fun and knowledge; the cost of such a gadget was rather expensive to be purchase just for fun. I got myself this power meter which is inexpensive. I like the huge display; the numbers are easy to read. It is very simple to use; just plug in the appliances that you want to measure and switched on the power. The function button can be pressed to cycle through the list of measurement parameters as follows.

1) Wattage, display the power consumption of the appliance

2) Display the energy consumption in terms of dollar cost

3) kWh (kilo Watt Hour), accumulated energy since operation.

4) Number of days, hours since measurement begins. (This helps to check against the kWh energy consumed and the accumulated cost run since measurement starts)

5) Voltage (Vrms measurement usually range from 220 - 240Vac)

6) Frequency (always 50Hz for measurement in Singapore)

7) Current (High current device usually requires thicker cable guage. High current flowing through thin cables can generate heat which leads to energy loss, and may result in fire.)

8) Power factor (PF range from 0.0 - 1.0. PF near to 1.0 indicates that the appliance has a better current to power efficiency, consuming all the power that was drawn)

9) Highest/lowest wattage detected. (The meter when monitoring the appliance over a long period of duration, is able to show the highest/lowest wattage detected)

10) Key in the latest electricity tariff rate..

11) Reset button to reset the measurements.

The features on the power meter are more than enough to measure household appliances. There is a current limit of about 13A which the meter can handle; the meter will give off a warning beep sound and cut of the power if it is overloaded. I just love this power meter, cheap and good enough for my energy audit.

It was when I started measuring my household appliance, that I started to learn the appliances that are energy consuming. It is difficult to judge base on the device, even though I am a trained engineer in electronics circuit design. I was shocked to find that many appliances are poorly design in terms of energy conservation. This is also the reason why I started this page. I would like to find out the power consumption of the appliance in a typical home. The step to start saving our earth starts by being aware of our energy consumption; this is also known as our carbon footprint.

Besides measuring power consumption, this power meter is also very useful in my area of engineering works.

This portable power meter helps to verify my electrical installation works. There are also times where 110Vac is used in our 230Vac electrical system in Singapore. This meter helps to check if the voltage step-down transformer installation is correct, before we plug in any expensive 110Vac equipment from oiverseas. It can also be used to check the wattage of your equipment so that the accessories with the correct wattage can be purchased and installed.

Power factor (range 0.0 to 1.0) indicates the efficiency of the current drawn from the power station. Poor power factor is cause by your inductive equipment (eg. Fridge, Fan, Motor etc..) at home or factory. A power factor of 1.0 is the best, indicating the lowest possible current drawn. A reading of 0.6PF or below indicates a poor power factor, and you will expect the current drawn to be higher. The good news is, it can be improve by installing a capacitor across the power line.

This meter measures the power factor which allows me to add in the correct amount of capacitance to correct the power factor close to 1.0. Power factor of 1.0 means that the current drawn by my equipment will be minimum. The meter will also show the drop in the current drawn, before and after the capacitance installation. For more technical information on correcting power factor, I have another delicated page explaining all the details.

In the course of designing products for the industries, this meter also helps me to verify my design in terms of the energy consumption. It helps me to improve the design, allowing the product to consume less energy.

With this measuring instrument, we will have a better idea of how we can improve our energy consumption.


   "If you can not measure it, you can not improve it.”
                                                                     Lord Kelvin (1824-1907)


I hope this page can provide the awareness to get you conscious about your carbon footprint. It will also serve as a platform to compare the consumption with the available energy saving products. The journey shall starts with my power meter. Let's get started.







My portable power meter packed with many features (description details on the left). Measure power from the plug.

1) Wattage

2) Accumulated electricity expense


saveOne power meter

3) kWh

4) Records of the number of Days & Hours since measurement starts

5) Voltage

6) Frequency

7) Current

8) Power factor

9) Highest/Lowest wattage detected
10) Entering the electricity tariff rate costing.


This power meter is purchased from saveOne logo.

Acknowledgement: some of the pictures on this page were taken from saveOne website. saveOne is a local company in Singapore, specialising in energy saving products and consultation services. They are also selling their various patented energy saving lightings products to promote green building to the industrial, hence reducing our carbon footprint in Singapore.

Website: , Email:

Address: 63 Hillview Avenue, #08-01, Lam Soon Industrial Building, Singapore 669569.
Tel: +65 6764 3333, Fax: +65 6862 6277


or click here to
Buy this Power Meter Now at the PIC-store



Other brand of power meter available in Sim Lim Tower (Sim Lim Tower, 10 Jalan Besar 208787)




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3. Home Appliances

Power Consumption



Note: the indicated elecrical costing is using the triff rate of $0.30/kWh


This is my electrical bill for my HDB house for the month of March 2012 from SP Services. The power consumption is estimated to be 363kWh which accounts to a bill of S$100.15. This is an estimation base on our electricity consumption for the pass few months. The tariff rate is 0.2759 for this quarter Jan-Mar 2012.

I am trying to measure all my appliances to see if I can estimate near to the indicated consumption of 363kWh per month. The list of contribution would propably comes from the following devices.

- Fridge
- Aircon
- Fan
- Computer
- TV and entertainment system
- Washing machine
- Lights
- Radio

It is time to find out the main culprit.






Home Lightings

Energy saving LED and Fluorescent lamp



Check out the various energy saving lamps here.



Hot/Warm Water Dispenser

Model: Bio Pure (KEN2)


water dispenserwater dispenser

reading reading measurement
Typical standby power consumption is 6.8W When dispensing water, the wattage shoot up to 21W Total energy consumption for 63 days + 1 hour operation totals up to about 60.91kwh costing S$17.15

Standby power: 3.5W

Typical: 6.9W (wattage), 0.077A (current), 0.36PF (power factor)

Highest Wattage detected: 2256W

Low Wattage detected: 3.5W


AC indicator lamp



AC lamps

Hardly any wattage and current detected from the AC indicator lamp found on the multi socket adaptor..


Wireless Door Bell

Model: Sonik


wireless door bell Standby power is 1.2W

Even if the loud door bell ring is activated, the consumption still remains at 1.2W.

The door bell transmitter outside the door is using a battery.


Electric Fan

Model: Aerogaz 16" stand fan AZ-163SF (60W)


Standby power: 0W

Speed 1 energy consumption: 34.2W, 0.159A, 0.95PF

Speed 2 energy consumption: 40.6W, 0.177A, 1.00PF

Speed 3 energy consumption: 45.3W, 0.190A, 1.00PF

Lab Bench Power Supply

Model: Kikusui variable DC power supply PAD 35-10L 0~35V 10A


14.3W consumption with no load to the lab bench power supply. Open DC voltage of about 0Vdc.


15.1W consumption with no load to the lab bench power supply. Open DC voltage of about 3Vdc.


Open DC voltage was tuned up to about 30Vdc. AC power consumption increases to 20.3W.


The current limits is purposely set very low to 0A. Consumption is now at 14.5W.


5Vdc open load. Wattage consumption is 15.2W.


5Vdc shorted load of 1A. This would have been a 5W load. Consumption is 27.9W. A 12.7W increased from the open load consumption.


Din rail MCB (Miniature circuit breaker), ELCB/RCD (Earth leakage circuit breaker)

Model: MOELLER PLS6-B6/2-AS (MCB 'B' 2Pole 6A 6kA), MOELLER PFIM-40/2/003-A (ELCB 40A 2Pole 30mA)


The circuit breaker and ELCB or RCD device uses very little energy. No power consumption was detected.


Charger for mobile phone (5V, 0.89A)

Model: Nokia C3


Not much power consumption when the charger is not plugged onto the mobile phone. Measured consumption is 0W. When the charger is plugged in, the consumption is about 1.3W.

Charger for bluetooth earpiece (5V , 0.55A)

Model: Sony Ericsson MW600


The bluetooth charger is similar to the mobile phone charger experiment. When the charger is plugged in, the consumption is about 0.7W.

Power Adaptor for laptop (19Vdc, 3.42A)

Model: Asus X23F 10" laptop


For this Asus laptop's adaptor, the consumption is more. When the adaptor is not plugged onto the laptop, the consumptionm measured is 0.3W, 0.014A.

When the adaptor is plugged onto the laptop, the consumption increases to 45.2W, 0.314A, 0.59PF

Then the laptop was switched on, the power consumption increases to 72.1W, 0.519A, 0.57PF.

The laptop was shutdown, and the power consumption drop back to 0.328A, 0.69PF. Should be about 45W.


Hair Dryer

Model: Rowenta (1500W)


This hair consumes a standby power of about 0.1W, 0.015A.


The hair dryer was switched to no.1, and the consumption is measured to be 755W, 3.26A, 0.98PF


Switching to no.2, the consumption now is measured to be 1460W, 6.3A, 1.00PF


Power Adaptor for Mini PC

Model: Giada Slim-N10 Intel dual-core Atom N330 1.6GHz, NVIDIA 9400M Graphics processor, 5x USB, 250Gb HDD, 2Gb DDR2 RAM, 802.11b/g WiFi, HDMI, Card reader


This Mini PC with power adaptor unplugged consumes about 0.5W. When it is plugged to the mini PC, the wattage increases to 3.6W, 0.053A, 0.25PF..


When the mini PC is switched on, the power consumption is about 28-30W, 0.21A, 0.55PF


Power consumption during standby with mini PC switched off.


Food Streamer

Model: Tefal, serie S07 (760W-900W)


When the streamer is off, power consumption is measured to be 0W. Turning on the "Keep Warm" features consumes about 835W, 3.55A, 0.98PF. The streamer will switch the streamer off when it reaches certain temperature threshold. This will keep the food warm while trying to keep the power coonsumption low.

With the streamer fully switched on, the reading is similar rto the power consumption of the "Keep Warm" feature.


LCD monitor

Model: 24" Philips 240B MWB1240I (230Vac 1.2A)


This monitor has a standby power of 0.6W.

When it is switched on, it consumed about 27W and can reach as high as 43W.


Measurement taken 26.7W, 0.19A, 0.56PF.


Personnal Desktop Computer

Model: Shutter PC, Intel Core 2 Duo CPU E7500 2.93GHz, 4Gb RAM, 250Gb HDD, DVD drive


The computer CPU system has a standby of 0.7W when it is plugged onto a socket but not switched on. Typical about 60W, and the highest reading meansured is >70W. Current is 0.361A, Power Factor of 0.82PF. When the computer is put into sleep mode, the power consumption drop down to 3.6W 0.067A 0.21PF..



Color Laser Printer

Model: Fuji Xerox CP205W


Printer on standby 11.5W to 750W

Printer reaching its peak 776.1W.

The laser printer standby power is about 11.4W and reaches to 750W every 10 to 20sec in a pulsing manner (0.139A, 0.33PF). Perhaps it is using the energy to warm itself every now and then. Current 0.139A, Power Factor 0.33PF. Measurement taken during the printing process is about 50W to 750W.


A4 paper scanner

Model: Fujitsu Scansnap S510 (16V 1.5A), Power adaptor (230Vac to 16Vdc 2.5A)


Scanner power adaptor consume 0.5W when it is not plugged onto the scanner. When it is plugged to the scanner, the standby power is about 0.8W.


The scanner reaches to about 17.7W (0.131A, 0.54PF) when it is turned on. During the scanning process, the consumption is about 26.4W.


TV tuner box

Model: MyGica (5Vdc 0.6A), Power adaptor (230Vac to 5Vdc 1A)


This TV tuner box is surprisingly using not much energy. The consumption is measured at 0W when the adaptor is not plugged onto the device, and reads 1.5W when it is plugged in. Turning on the TV tuner consume only 3.3W.

Water Kettle

Model: Tefal VITESSE BF21 (2000-2400W)


The water is a simple heating element device. The load is resistive in nature. When not activated, the kettle consume 0W.

During the water heating process, the power consumption measured was 2140W (9.28A,0.98PF)


Battery Charger AA/AAA

Model: GP Power Bank GPPB50GS (230Vac 0.175mA, or 12Vdc 0.75A)


The battery charges has a standby power of 0.7W (0.008A) when no battery is under charging. The charging is a pulsing process. The wattage taken pulse between 3.1W & 0.7W when one AAA size battery was inserted for charging. The wattage goes up as more batteries (1x AAA and 2x AA) were inserted. The pulse is between 6.9W & 0.7W (0.055A, 0.5PF)


40" LCD TV

Model: Sony KDL-40EX400 (155W)



See in this short video clip how the wattage increase as the TV starts to turn on. MVI_8968, sony lcd tv power consumption.AVI



The standby power for this Sony TV is quite high. 10.1W (0.095A, 0.42PF) was measured. It is equivalent to a lamp turning on.

The TV was switched on with the TV show running. The power consumption at this point in time was about 114W (0.546A, 0.89PF) .

There is this video footage capture for your reference. In the video, you can see on the power consumption rises as the TV was switched on.

MVI_8968, sony lcd tv power consumption.AVI


DVD player

Model: Pioneer DV-595K (7W)


Standby power 0.7W measured is the same as specified in the user manual. Thie meter seems quite accurate for our energy audit.


The standby power for this DVD player is 0.7W (0.008A).

When the player starts to playback video on the CD, the measurement taken was 6.5W (0.057A, 0.51PF). Energy consumption is quite reasonable for a player.

It increases slightly at time to 7.2W (0.6A, 0.49PF)


Induction cooker

Model: TAIYO TH-ID19 (1900W)





See in this video clip how a induction cooker consume the energy. MVI_8983, induction cooker.AVI


The standby power is about 4W (0.25A, 0.1PF) . When it is switched on without any pot, the reading was 10.8W (0.141A, 0.29PF). The induction cokker is quite intelligence. No power will be activated when the cooking pot is not on the stove.

A stainless steel pot fillled with water was placed on the cooker stove. The induction cooker detects the load and starts to consume a lot of nergy to boil the water. The power consumption was 1974W (8.691A, 0.99PF). The induction cooker power factor is surprising good. The load may not be inductive in nature, or perhaps capacitors are added to the cooker to correct the power factor. By correcting the power factor of your appliances to a value close to 1.00, the current it draws will be at its minimum. This helps to reduce losses, reduce of cable size, prolong lifespan of your cable, generate less heat, etc.... many benefits. The benefits will not be significant but it is better to have it optimised than a design that isn't.

The following footage shows how the power consumption changes on this induction cooker.

MVI_8983, induction cooker.AVI


NAS Network Attached Storage

Model: Netgear ReadyNAS Duo, Power adaptor (230Vac to 12Vdc 5A)


The power adaptor was not plugged onto the NAS, gives a reading of 0.4W. This means that the power adaptor doing nothing is actually wasting the electricity when connected with the mains socket switched on. When plugged onto the NAS device, the standby power is 0.8W.

When the NAS was switched on, the power reading was 23W (0.17A, 0.53PF).


Home Wireless Router

Model: Dlink DIR-655 (12Vdc, 2A)


Wireless router's power consumption seems ok. Measured power during operation was 6.1W (0.051A, 0.51PF).


AV Wireless Transceiver

Model: AV@AirPro


This wireless AV transceiver consume about 2W. Quite little energy.


Cable TV setup box

Model: STARhub Hubstatio DC162SHB


The STARhub setup box has a significantly high standby power required. The measured power during standby was 20-25.6W (0.184A, 0.59PF).

The setup box reaches 27W (0.187A, 0.6PF) during start up, and consume 26.5W (0.19A, 0.59PF) during the cable TV show. The increase in power from standby is relatively low. This device has the most energy wasted during standby. Turning the machine off to a standby mode will only save you 1 to 2W, but actually wasting about 25W.


The little multimedia Zen10 box consume much less energy compared to the STARhub setup box. Zen10 consume only about 0.4W during standby, and 6.2W (0.052A, 0.42PF). If the power adaptor is not plugged onto Zen10, the wasted power on the adaptor is measured at 0.2W.




The fridge consumption seems rather stable. Different from what I have expected. I thought it should be like a pulsing type of power consumption pattern. Switching on and off the compressor when neccesary to cool the fridge. Typical wattage consumption was about 209.1W and can reach as high as 388.7W.

The meter was put on the fridge for another period of 32 days. The following reading was taken which was more accurate.

Wattage at the point in time: 204W

Current at the point in time: 1.126A

Power factor at the point in time: 0.78

Lowest wattage detected: 17.3W

Highest wattage detected: 440.5W

Voltage range: 228.9 to 230Vac (50Hz)

Total measurement period: 31days and 23 hours

Total energy consumed: 149.1kWh

Total electrical bill amount: $44.73 (base on electricity tariff rate $0.30/kWh)


I was shopping around to take a look at the latest energy efficient fridge. The consumption for these fridge as displayed was about 500-700kWh per annual. The efficient is much better. I am assuming the measurement was took without considering the typical scenario of opening of the fridge door. Opening the door increases the temperature inside, which means that more energy is required to cool it down.


Washing Machine

Model: National NA-FSSY6T


Washing machine standby power is 1.3W - 1.8W (0.006A, 0.42PF)

Filling up the washer with water consume 8W (0.038A, 1.00PF)

Washing process rotate the motor clockwise and anti-clockwise. The consumption is pulsing between 100W and 340W (0.7A and 1.4A 0.19PF). The power factor becomes lower when the motor starts to be activate. Motor is an inductive load causing the power factor to becomes lower.

After the washing process, the washing machine drained the water. This activity consume only 4.8W (0.021A 0.85PF).

The washing machine starts to spin to squeeze out the water. The machine controls the spin. I can see the wattage moving slowing from about 230W to 260W as the spin starts to pick up. When the spin reaches its momentum, the wattage starts to drop gradually to 200W. At top spin the wattage is about 200W. The initial start up requires more torque to spin the load, therefore more power was required. When the spin reaches it top speed, the torque required was less, therefore less power was required. This activity consume an average of about 230W for 2 min.


The whole washing process takes about 45min to 60min. Total wattage consume is about 0.352kWh for two wash (medium load). This comes up to about 0.176kWh of energy consume for each washing.


Model: TEFAL Turbo Delice 26L


oven baking tart oven baking tart

My mother was baking the pineapple tarts for Chinese New Year, when I took this measurement. I wanted to find out how much electricity is used to bake the tarts.

The tarts were baked at about 180C for about 20 minutes. A total of 7 trays (36 pineapple tarts per tray) were baked in 4 batch. The cost of electricity is $0.42. This means that the electricity cost for each batch of baking cost about $0.105, each tray cost $0.0525, or each pineapple tart cost about $0.0015. The bill seems quite affordable.

Wattage at the point in time: 2900W

Current at the point in time: 12A

Power factor at the point in time: ---

Lowest wattage detected: ---

Highest wattage detected: ---

Total measurement period: 1 hour 20 minutes

Total energy consumed: 1.431kWh

Total electrical bill amount: $0.42 (base on electricity tariff rate $0.30/kWh)


Soldering Iron

Model: GOOT TQ-95 Quick Heat Soldering Iron 200W/20W



When the soldering iron is first switched on, the wattage measured is 60W.

As the iron gets heated up, the temperature starts to drop to a constant wattage of 25W (0.1A, 1.0PF)

There is this quick heat button to heat up the iron faster (can only press for no longer than 10sec).

When this button is pressed, the wattage shoot up to about 128W (0.523A, 0.98PF).

The soldering iron is a resistive load, which is why the power factor is always quite close to 1.0PF.


Cost of running the soldering iron for 1 hour = 25W/1000 x 1hour x 0.30kWhr = $0.0075 (about 1 cent every hour)




- Top energy consuming devices

- Many switching AC-DC power adaptor do consume energy when it is left switched on. The power factor from all these advance switching adaptor seems quite poor.
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Power meter, energy consumption measurement, energy audit, energy saving, save energy, ECO friendly