Elto EMA-1 Power Meter

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A low cost appliance power usage meter with two tarriff rates. For each tariff rate you can control the activation day (or a set of days) and an activation time. The EMA-1 requires two LR button cell batteries. These are supplied with the device.

Close-to-identical devices:


Very similar devices and differences:

Watts Clever Plug-in Energy Monitor
  • Built in rechargeable battery
  • CO2 estimator

If you are lucky enough to live in Palmerston North the local libraries will lend you an EMA-1 for two weeks at a time. 

From the February 2010 library newsletter: 

"Power meters are available for checkout at the Central Library and at any of the Branch libraries including the Mobile. This is an excellent opportunity to check your own home energy use, prior to making any improvements on energy efficiencies. It checks out for two weeks, at a cost of $2. The meter comes with an instruction booklet. Get yourself ready for the coming winter! Just enquire at any of the circulation desks and issue it on your library card".

The library have also created a nifty instruction and information booklet for the meter. They preset the meter for you at 22c on peak and 19c off peak which might be too low if you are on a prepay meter - but they don't mind if you change it. You can even find out when they have one available.

Other libraries may be interested in getting one or a similar meter if you ask. They could benefit from the experience already gained by Palmerston North and can use the same instructions.

Feature table:

Clock (time/day)
Real time line voltage
Real time line frequency (Hz)
Real time appliance power factor
Real time appliance watt usage
Real time appliance amp usage
Watt peak usage and day and time of peak usage
Total recorded kilowatt-hours (Kwh)
Total price of kilowatt-hours (Kwh) used
Total recorded on-time of attached appliance
Number of tariffs / kwh cost breaks: 2
Tariff one: total recorded kilowatt-hours (Kwh) and appliance on-time in this price category
Tariff two: total recorded kilowatt-hours (Kwh) and appliance on-time in this price category
Set day to apply each tariff and on-time

Online Retailers: (Product available for purchase on-line)

Dick Smith
Woolworths/Countdown Supermarkets (requires login)
PMB Electronics (with example appliance usage stats)

Offline retailers: (Product available for purchase in-store only)         

The Warehouse


CDB Goldair (Elto brand)


NZ Consumer Magazine review of Elto EMA-1 (Included in short online article about power saving gadgets)
User experience review on NZ govt sponsored sustainable lifestyle website
The Elto meter is included in a review of power meters by the Christchurch based Press newspaper 


The EMA-1 is manufactured in China by Cixi-Yidong Electronic Co, Ltd. 

Price guide:

Under NZ$40


LR44 button cell x 2

Technical people:

Adafruit mod details