Newegg.com has the P3 International Kill-a-Watt Electricity Usage Monitor for $14.99 plus $1.99 Shipping.
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- Compatible with inverters; designed for use with AC 115-volt appliances n
- Electricity usage monitor connects to appliances and assesses efficiency n
- Large LCD display counts consumption by the kilowatt-hour n
- Calculates electricity expenses by the day, week, month, or year n
- Displays volts, amps, and wattage within 0.2 percent accuracy