Formula
For a resistive load, power is the product of voltage and current:
watts = volts × amps
Energy is that power, in kilowatts, times hours. The electricity cost page starts from watts you already know and adds a price.
Assumptions
- Voltage and current are measured at the same time.
- The load is steady for the hours you enter.
- Power factor is left at 1. A UPS page is the one that asks for it.
Worked example
120 volts at 8 amps is 960 W. Over 3 hours that is 2.88 kWh.
Input definitions
- Voltage
- The supply voltage, such as 120 volts on a household circuit.
- Current
- The amperes the load draws while it is on.
Limitations
This is a planning estimate. The rate, sun hours, and losses are numbers you type. It is not a utility bill, a solar design, or a room-by-room load calculation.
Questions
Is this the same as the wattage on the label?
Only if the label matches volts times amps. This page starts from the electrical measurement, not from a printed wattage.
Where is the price?
There is no rate here. Take the kilowatt-hours to the kilowatt-hour cost page if you want a cost.