Power meter with Pulsed Output?

Other Hardware Home Automation
2

With the pulse length being 100 mS there is almost no difference between using RISING and FALLING. Pick one.

All the interrupt has to do is add 5 to a global volatile unsigned long that keeps track of kilowatt hours:

volatile unsigned long kWh = 0;

void ISR1()
    {
    kWh += 5;  // Each pulse represents 5 kWh
    }