Basic Energy Audit: Typical Nuclear Family House

The one thing that baffles me most about Nigerians, is our unwillingness to read. We are living in unforgiving times, when ignorance is not only a lame excuse, but a precarious stance to begin with. — Rotimi Babalogbon

For the sake of simplicity, I shall assume a typical house to be a two bedroom flat(young nuclear family). This apartment will also be assumed to have one Home Entertainment System(consisting one LCD Tv, home theatre system with decoder) in the living room, one Medium sized refrigerator, two 1hp(horsepower) Air Conditioners(living room and master bedroom), One laptop, three mobile phones, eight energy saving light bulbs(24W each), and occassional devices (like pressing iron, microwave, blender).

How much energy does this apartment really need per day depends on the individual wattage of each of the devices, coupled with the amount of time they are on for(duty cycle). For example, a 2012 model of a 42-inch LCD Tv consumes around 400 watts(per hour). If that TV is allowed to run for ten hours per day, that is 4000 watt hours. If the light bulbs all run from 7pm to 7am @24W per bulb, that comes to 2,304 Watt hours. Electric bills are in KWh i.e kilo watt hours. Hence, the cost of running the LCD above per day is current rate per KWh multiplied by 4KWh per day; The bulbs will be 2.3KWh multiplied by same rate.

To save you the boredom, I’ll assume a running time of six hours for the Home entertainment system(600W), ten hours for the refrigerator(650W)(due to thermostats in these devices, they actually shut down at intervals to maintain target temperatures), twelve hours for the bulbs(192W), twelve hours for the ACs(1,500W) and one hour for the occasional devices(1,200W).

The daily demand for energy for this kind of house will be 31.6KWh. If this house were to run entirely on PHCN, at a rate of per KWh, the monthly bill would be 31.6 x 30 x 17 = N 16,116 monthly; In a year that comes to 
N 193,392.

So, how much energy does such a house need at peak demand period? It depends on the period of the year. But realistically, a peak demand(weekend evenings) the peak demand will be around 4.2KWh.

That figure is the magic number that is needed for generator sizing, inverter sizing and even solar power planning.