How to Determine the Size of Solar Electricity System for Your Needs

Components that make up a Solar Electric System

There are 3 major components of a solar electric generating system;

  1. Solar Panels: which produce electrical energy from the sun
  2. Battery: to store electrical energy produced by the solar panels
  3. Inverter: converts direct current produced from the battery or solar panels to alternating current required to power your electrical devices.

Note that there are battery-less solar systems too. If you only need electricity only when the sun is shining then you only need a solar panel and inverter. And if your electrical appliance runs on direct current only, then you only need the appropriate amount of solar panel or panels with a direct current voltage regulator installed.

In advanced countries with 24 hour supply of grid electricity, batteryless solar systems are connected to the grid. The overall goal here is to reduce the cost of grid electricity being paid for by the owner of the solar system. Once the solar panels generate enough electric power for the day, the excess is sold off to the grid. A sophisticated device that calculates the energy produced by the solar system and the excess that is sold off is installed with the system.

Solar Panel Sizing 

Solar panels are produced in different power output ratings. There are 10 watts solar panels, 20 watts, 30 watts and so on. A standard solar panel is rated at a power output of around 300 watts. In determining the size and number of solar panels you will need, you will first need to find out your total power consumption requirements.

To know the power consumption of your electrical appliances, check under or back of the appliance.

Once you know the total power requirements of your electrical appliances you can then correctly determine the size and number of solar panels required.

Let’s say the total power consumption of all your electrical appliances is say 3000 watts, then this means you will need ten 300 watts solar panels. Assuming not all your electrical appliances are working at the same time then the panel sizing just calculated above will be adequate. Otherwise you may need to add say one more 300 watts. This is because the solar panels are not 100% efficient.

Suitable Battery and Sizing

Big sized batteries suitable for use with a solar electric system produce a direct current of 12V.

Battery capacity is the key factor here. It is the maximum amount of power the battery can store.

Batteries suitable for the solar system are deep cycle. Deep cycle batteries are designed to discharge to almost it’s full capacity without damage. Say 80 to 90% of total capacity.They look like car batteries. Note that most car batteries are not deep cycle.

There are two major types of battery in the market;

  1. Lead acid battery
  2. Lithium battery

Lead acid batteries  are very common and cheap. Even though lead acid batteries can be designed for deep cycle use, it is advisable you don’t discharge more than 50% of its capacity to extend battery life. It is also advisable to use flooded lead acid batteries rather than seal lead acid batteries. They last longer when properly maintained. Lifespan of lead acid battery is between 1.5 to 2 years

Lithium batteries are true deep cycle but are expensive. They can support discharges of over 90% of their capacities without damage. They can also support recharge cycles of between 1000 – 3000 times lasting 3 to 5 years if properly used.

Battery Sizing 

Battery capacities are usually expressed as Ah (Ampere hours). To express as Wh ( Watt hours) it should be multiplied by the supplying voltage of the battery which is usually 12V ( V stands for volts). Also note that 1kWh ( kWh stands for Kilowatts hour) = 1000Wh.

For instance, a battery rated 300Ah, and multiplied by 12V gives;

300 × 12= 3600Wh or 3.6kWh.

This means that the fully charged battery can deliver a power of 3.6kW consistently for 1 hour.

Referring to the example on solar panel sizing, recall that we sized for 3000W. Since it is reasonable that all electrical appliances can not all be put on at the same time for 24 hours, we can conclude that on the average, a power of 1500W  or 1.5kWh is being utilized every hour. Recall that our calculated battery capacity is 3.6kWh. A little consideration will show that if 3.6kWh is divided by 1.5kW ( which is the average power consumption per hour, it means that a single fully charged 3.6kWh battery will power your electrical appliances for ; (3.6÷1.5= 2.4 hours) 2.4 hours or 2.4h, (h stands for hours). So if you want a 24hour supply you divide 24 hours by 2.4 hours which equals 10. This means you will need ten 3.6kWh capacity batteries.

In truth if you are using lead acid batteries you will need much more.

Since it is not safe to discharge  above  50% the rated capacity in order not to damage the battery, then ten batteries will run for 12 hours. That is you need 2 × 10 lead acid  batteries to run for 24 hours. But if it’s lithium batteries which can support almost full discharge without damage, then near 24 hours supply is possible with the calculated 10 batteries. 

In summary of this section, if it’s lead acid battery, then you will have to double the battery size / number to run for the number of hours it has been designed for. If its lithium battery then increase battery size / number by 10-20 %.

Inverter Sizing

It is better to get a much bigger inverter than what is required. For a 3000W power consumption you can go for a 5000W rated inverter. This will give the inverter much headroom to operate safely. Inverters are prone to overheating when loaded near it’s full capacity.

Backup Generator

Your solar electric system will not be complete without a backup generator. When the solar power and batteries run out. The back up generator can restore power and at the same time charge the batteries for another cycle of use.

Generator Sizing

For the generator to last, it should run at 50% its rated capacity. So let’s say all your household electrical appliances are rated 3000W, then get a backup generator of 6000W.

Understanding the Wire Colours connected to Electrical Appliances

Wire Colours connected to Electrical Appliances
wire colours

All electronic appliances comes attached with a power cable for connecting to electricity outlet in your house.The power cable may contain 2 or 3 wires. A power cable with 2 wire colours are in RED and BLUE. A power cable with 3 wires have the colours GREEN, RED and BLUE.

Meaning of the wire colours

The Wire colours have their meanings and It is briefly explained below;

Red colour : Live wire

Brown or Black colour : Live wire

Blue or White colour: Neural wire

Green or Yellow colour: Earth wire

In some places, the live wire is black in colour and the neutral wire is white.

The red or brown wire is “LIVE” as the name implies, electric current flows through this wire. The live wire supplies electric current to the appliance. You should take care when you handle this kind of wire. It can cause an electric shock

The blue wire is “NEUTRAL” . This wire do not give a shock upon touching it or show a red light through a tester. In reality it carries electric current back to the power source. It is the neutral wire that allows the current to alternate. Neutral wire is an integral component of an AC power system.

The green wire is “EARTH” . The purpose of this wire is to remove excess electric charges that might be on the connected appliance and drive them into the earth. It is good practice to earthen electrical appliances to prevent any form of electric shock upon contact. The Earth wire is usually connected to a metal rod driven into the ground.

Some electrical appliance come with just the live and neutral wire. This is Ok. But you are always at a risk of receiving electric shock from contact with the appliance when connected to electricity. This usually happens when the electrical appliance is faulty.

The live wire supplies current to the appliance, the neutral wire carries it back and the earth wire is to serve as protection from electric shock.

Understanding Power Ratings of Electrical Appliances.

Every household electrical appliance, always have its power rating labelled on it. Power rating is very important as it gives information regarding its power consumption.

Knowing the power consumption rating of your electrical appliance will help understand and analyze your electrical bills. It will also help when you have to determine the capacity of generator or inverter you will need to power up your appliances.

There are two important information to look out for in a power rating label;

  1. Voltage rating  (v)
  2. Power rating   (w)

You should always check the voltage rating of any appliance you buy, this is necessary to make sure it is not different from the voltage rating supplied to your home.

Since electrical bills are determined by power consumption you should always check power ratings of your electrical appliances to have good idea of how much you would be paying for electricity by the end of the month.

Power consumption on electricity bills is usually measured in kilowatt hour (kwh).

For example, an electric fan with a power rating of 50w will consume 50w in one hour or 50/1000 kwh = 0.05kwh.

An electric cooker with power rating of 2500w and used for 2 hours everyday will consume 2500 x 2 = 5000w in 2 hours or 5kwh. (Note: 1kw = 1000w). Doing this every day for the month you consume 5 x 30 = 150 kwh! Just for using the electric cooker!..

Total power consumption of all active electrical appliance in your house is added up by your electric meter. You pay for total electrical power (kwh) consumed every month.

It is very important to switch off electrical appliance when not in use to save cost of electricity bills.


Direct current (DC)

The Direct current (DC) is simply electric current that flows in one direction. It usually flows from a battery source. It also means electric current with one polarity of current or voltage.

Uses of DC

DC is often used to power low voltage appliances such as flashlights, toothbrushes, calculators, telephones and so on, although it can also power high voltage appliances.

Sources of Direct Current Supply

 Common sources of DC supply includes solar cells, batteries and DC generator.

Drawback of Direct current (DC)

The major drawback of Direct current (DC) is that it cannot be transmitted through long distances without considerable power loss. The power plant or source of direct current (DC) supply must be within 3km of the appliance which implies that direct current power plant/supply must be installed in every household.

Alternating Current (AC)

 Alternating current rapidly changes in direction. AC is transferred at very high voltage (kilovolts) over long distances and then stepped down with a transformer to between 100-240 volts at point of use.  

Uses of AC

AC is often used to power appliances that require higher voltages examples include fans, air conditioners, cookers, tvs ,  water heaters, pressing irons and so on

Advantage of Alternating Current

The major advantage of AC is that it can travel hundred to thousands of kilometers without considerable power loss making it possible for the location of central alternating power supply stations far from point of use.

Comparing Alternating to Direct Current

It can be argued that AC holds no practical advantage over DC. As stated earlier, DC is preferred over AC for low voltage appliances while AC is preferred to DC for high voltage appliances. However it is possible to build power supply/distribution systems that are more efficient with AC than DC and this is one reason why the AC is far more popular.

What you need to know about MTN’s LUMOS MOBILE ELECTRICITY

                                          Lumos Mobile Electricity

Lumos mobile electricity comes packaged with;

  • 80W solar panel
  • One indoor unit (unit that stores electricity charge generated from solar panel)
  • 2 led bulbs
  • Usb and pin phone charger
  • DC to AC Converter

Lumos mobile electricity specifications.

300Wh Lumos Smart Solar PayGo  indoorUnit (MTN Yellow Box)

80W Solar Panel with cable

Two USB ports (5V DC / 2.1A)

60W DC to AC Converter (60W Inverter)

Two Bright LED Bulbs

Four DC Output jacks (12V / 2A)

Two Car Cigarette Sockets (12V / 8A)

6 hours Charge Time (Bright Day)

How it works.

Solar panel charges the battery in the indoor unit using energy from the sun.

(the solar panel must be installed on the roof to maximize energy use of the sun.)

You plug your electrical appliance to charged indoor unit.

Lomos Mobile Electricity System



What lumos mobile electricity can power;


Dc fan

Charge mobile phone

Small LED/LCD tvs (up to 14 inches)


Hair clippers

Dc light bulb

Small 60W AC  standing fan

Lumos Mobile Electricity and some appliances it can power

What lumos mobile electricity cannot power;

Air conditioner

Water heater

Electric kettle

Electric cooker

Desktop computer

Microwave oven


Ceiling fan


Washing machine and other heavy electrical appliances.

Cost and fees.

As of writing, you can get the unit for 20,000 naira at any MTN office and

Pay subscription fees daily, weekly or monthly;

1 day:  230 naira

10 days: 1800 naira

20 days: 3300 naira

1 month: 4500 naira

3 months: 12,600 naira

1 year: 46,720 naira

5 years: 219,000 naira

In short, you are paying installmentally for a period of 5 years.

You must pay for at least 20 days usage every month. After regular use for 5 years, the system becomes fully yours.

How to get Lumos Mobile Electricity.

Sign up at any MTN office with;

Your MTN Sim card

Valid ID card

2 guarantors

Install with the help of qualified/authorized professional.

Pay for electricity use using your MTN charged mobile phone 

How long lumos mobile electricity lasts when powering appliances.

This is the most frequently asked question. Depending on the number of valid appliances connected to the unit, when fully charged, can power appliances for 2- 8 hours. For very small appliances such as charging of phone and laptop, the device can be powering up these devices for almost 24hrs assuming a very bright day. The 2 led bulbs that comes with the unit can be powered up for 5 hours assuming the device is fully charged. It is best to use lumos mobile electricity to power only DC appliances for maximum enjoyment.

Is obtaining lumos mobile electricity worth it.

For low income earners; YES, the unit should cost around 200, 000 naira as onetime payment, so for those that can’t afford that much can obtain the unit with a downtime payment of 20,000 naira plus subscription fees of between 3,300 – 4500 monthly payments for the next five years. Also the system will be serviced free of charge during those five years as long as you don’t void the warranty.

For high income earners; NO, there are better solar/inverter alternatives  out there starting from around 150,000 naira onetime payment.