Energy Saving Electronics

Saving energy for a better tomorrow

Power Measurement

Plug-in electrical power monitors

Over the past few years, low cost electrical power monitors have become available which make it easy for anyone to check the power consumption of anything that plugs into a standard wall socket.

Prices of these units vary widely, but can be as low as $25.

Typically these devices can measure voltage, current, line frequency, VA, and power factor,  as well as watts and watt-hours (commonly killowatt hours).

The measurements that matter for energy efficiency assessment are these last two.  Some offer the option of entering a cost per unit of electricity and will display the cost of the electricity used over a period of time.

For electronic devices with power consumptions measured in tens or hundreds of watts, killowatt hours measurement may not be particularly useful.

The accuracy of the devices is typically a few percent, but the greater problem is resolution (i.e. the minimum level of power that can be displayed). 

Normally this is one watt which is perfectly OK when measuring the operating power of a television taking 200 watts, but is of no use when measuring a standby power of one watt or less.

There is no real solution to this but, on the other hand, devices that consume less than one watt are not likely to be major contributors to your overall energy consumption.

Wireless electrical power monitors

These monitors measure the total power being used in the home rather than that of individual items.

They consist of two parts, a sensor a transmitter which is fitted close to the electricity meter, and a receiver which enables the measurement information to be seen in a convenient position.

These devices normally have the ability to log electricity consumption over a period and to convert it directly into cost by entering a price per unit of electricity.

Again, prices vary widely but are typically in the $50 to $100 region.

Plug-in electrical energy monitor

Typical plug-in electrical monitor


Wireless energy monitor

  Typical wireless energy monitor