Generators in Nigeria: choosing, using and staying safe

Types of generator

Choosing the right size

Size is about how much you run at the same time. Generators are rated in kVA or kW. A rough link is kW = kVA x power factor, and the power factor is often about 0.8, so a 5 kVA generator may give around 4 kW of real power. Check the rating plate to see which figure is quoted.

1. List the appliances you want to run together and add up their running watts.
2. Allow extra for motors (fridges, freezers, pumps, air conditioner compressors). They draw a surge when they start, sometimes several times their running power.
3. Add a safety margin and pick a generator that will normally run at roughly 50-80% of its rating. Running far below that wastes fuel; running at its limit wears it out and risks overload.
4. If you plan to use an air conditioner or pumping machine, size for that load first, not last.

Working out running cost

Fuel is usually the biggest cost over time. You can estimate it yourself. Find the manufacturer's fuel use in litres per hour at about half and three-quarters load, then divide the fuel cost per hour by the power you actually deliver.

1. Cost per hour = litres per hour x current fuel price.
2. Cost per kWh = cost per hour divided by the kilowatts you are using at that moment.
3. Add servicing and oil, and the purchase cost spread over its expected hours of use.

Safety: carbon monoxide, fuel and wiring

• Never run a generator inside a house, garage, shed, corridor, balcony or any enclosed or partly enclosed space, even with doors or windows open. Exhaust contains carbon monoxide, a colourless, odourless gas that kills quickly.
• Place it outdoors, as far from doors, windows and vents as practical, with the exhaust pointing away from the building. Do not place it where fumes can drift into a neighbour's home.
• Consider a battery-powered carbon monoxide alarm in sleeping areas. Headache, dizziness, nausea or confusion while a generator runs are warning signs; get into fresh air and seek medical help.
• Store fuel only in proper containers, away from the generator, living areas and heat or flames. Stop the engine and let it cool before refuelling, and never refuel while it is running.
• Connect to your wiring only through a proper changeover switch or automatic transfer switch installed by a qualified electrician. Never plug a generator into a wall socket to power the house; this can send electricity back into the lines and seriously injure or kill people working to restore supply.
• Keep it dry and covered from rain, use correctly rated extension cables, never overload it, and follow the earthing instructions in the manual.

Installing and housing it

• Choose a level, stable, well-ventilated position, ideally on a concrete plinth, with space around it for airflow and servicing.
• Use a weatherproof canopy or housing that still lets exhaust and cooling air flow freely.
• Plan the fuel route and storage safely, and chain or fence it against theft.
• Think about noise: the neighbours matter, and some estates and local authorities have rules on generator location and noise.
• Have the changeover or automatic transfer switch wired by a qualified electrician, with correctly rated cables.

Maintenance that saves money

• Follow the service schedule in the manual for oil and filter changes; heavy daily use means more frequent servicing.
• Check the air filter, spark plug (petrol) or fuel filter (diesel), coolant (water-cooled diesel) and starting battery regularly.
• Run it under load briefly once a month if it sits idle, and avoid leaving old fuel in it for long periods.
• Keep a simple log of running hours, servicing and repairs. It helps you spot problems and shows value if you resell.
• Use a trained mechanic or the maker's service centre, and keep spare parts such as filters on hand.

Buying sensibly

• Check that the engine and alternator brand are genuine and that parts and a service centre are available near you.
• Ask for a demonstration under a realistic load before you pay.
• Get the warranty terms, the receipt and the serial number in writing.
• If buying fairly used, ask for the running hours and service history, inspect for leaks, smoke and unusual noise, and have a mechanic check it.
• Compare the full cost: purchase, fuel, servicing and expected life, not just the price tag.

Using a generator with solar

Many households use solar and a battery for everyday loads and keep a generator for heavy loads or long cloudy spells. Some hybrid inverters can start a generator and charge the batteries from it, which cuts the hours it needs to run. This is worth planning together with your installer.

Checklist: questions to ask any generator seller

• What are the running watts and starting watts, not just the kVA figure?
• What is the fuel use per hour at half and three-quarter load?
• Is the engine and alternator brand genuine, and where is the nearest service centre?
• What does the warranty cover, for how long, and who handles claims?
• Can I see it run under load before paying?
• Is a canopy, changeover switch or automatic transfer switch included or recommended?
• What is the recommended servicing interval, and what spare parts should I keep?
• Can you provide a receipt, serial number and written terms?