D. Thomerwald says:
From my research, the 4660 calculates your power consumption in dollars and cents, hourly, Daily, monthly and yearly. It also has a batery backup so that if the outlet loses power it remembers the data and continues reading when it is powered back on.
The 4400 displays usage in Killowatt hours, so with the info, your electrical bill and a calculator you can figure out the cost, assuming you can do math. Now there are 3 kinds of people in the world. Those who can do math and those who can't. Since I am in the latter category, I just purchased the 4460. Worth the extra $15 IMHO.
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David H. Johnson says:
Actually, according to their web site it does have battery backup:
http://www.p3international.com/products/p4460.html
However, people are confused about what battery backup means. With the P4460 once you unplug it from the wall the display is disabled and it no longer records data, however it _does_ retain the information that has been collected thanks to the battery backup. Once the device is plugged back in data can be displayed and more data collected. The user entered settings for price per kWh are also retained. The P4400, on the other hand, does not have battery backup and loses all data once it is unplugged.
credit to amazon customers.
http://www.amazon.com/whats-differen...sin=B000RGF29Q