Inverter sizing starts from one question: what is the most your home draws at a single moment? The calculator sums the wattage of every appliance you mark as running at the same time, adds 30% headroom for motor start surges (fridges and pumps draw several times their running wattage for a moment), and divides by a 0.8 power factor to convert watts to the VA rating inverters are sold in. The result rounds up to the standard sizes sold in the Nigerian market, from 1.5kVA to 15kVA.
Heavy heating loads dominate everything. An electric iron is 1000W and a 1.5HP AC is 1200W: each one is the load of a whole room of lights, fans and electronics. That is why the iron, microwave and pumping machine default to not running at the same time; most homes use them one at a time, and sizing for them simultaneously buys capacity you rarely need. The battery bank is sized differently, from daily energy rather than peak: the fridge cycles its compressor so it counts at 35% of its wattage across the day. Lithium banks can be drained to about 80% of capacity while tubular should stop at 50%, which is why the same backup target needs more tubular units than lithium.
Panels are sized to replace your daily energy at about 5 peak sun hours and 75% system efficiency. The cost figures are rough market component prices plus 10 to 15% installation, shown as a range and clearly an estimate: real quotes vary by brand, location and the state of the naira. The payback strip compares the installed cost against what you currently burn monthly on generator fuel. Use the installer quote form for firm numbers. Estimates only, not engineering advice.
Frequently asked questions
What size inverter do I need for my house?
Size the inverter to the most your home draws at one moment, not the number of rooms. Add up the wattage of everything that runs at the same time, multiply by 1.3 for motor surge, and divide by 0.8 power factor to get the VA rating. As a rough guide: lights, fans, TV, fridge and phones fit a 1.5kVA inverter; add a few more appliances and you are at 2.5 to 3.5kVA; run an AC or electric iron and you need 5kVA or more. Build your actual appliance list in the calculator above for a size based on your home rather than a rule of thumb.
What size inverter can carry a fridge?
A typical home fridge draws around 200W running but needs surge headroom for the compressor start. A 1.5kVA inverter carries a fridge plus lights, fans, TV and phone charging comfortably. The real question is everything else running at the same time: add up the wattage of what runs together, multiply by 1.3 for surge and divide by 0.8 power factor, which is exactly what this calculator does.
How many solar panels do I need for a 3 bedroom flat in Nigeria?
It depends on energy use, not the number of rooms. A 3 bedroom flat running lights, fans, TV, fridge and electronics typically uses 4 to 8 kWh per day, which needs roughly 3 to 6 panels of 550W at Nigerian sun levels (about 5 peak sun hours and 75% system efficiency). Add air conditioning and the count rises quickly. Build your actual appliance list in the calculator for a number based on your home, not a rule of thumb.
Lithium or tubular battery, which should I buy?
Lithium costs more upfront but you can use about 80% of its capacity, it lasts 2 to 4 times longer, charges faster and needs no maintenance. Tubular (lead acid) is cheaper per unit but you should only use about 50% of its capacity, so you need roughly 1.6 times more nameplate capacity for the same usable backup. Over the life of the system lithium usually wins; on a tight budget tubular gets you running for less today.
Can an inverter carry an AC or electric iron?
Yes, if it is sized for it. A 1HP AC adds about 850W and a 1.5HP about 1200W of continuous load, and an electric iron or microwave adds 1000W or more. These heavy loads are why a system sized only for lights and fans trips when someone irons. Either size the inverter for everything running together, or keep heavy appliances off the inverter circuit and run them only on mains or generator, which is what the same time checkbox models.
What does a full solar system cost in Nigeria?
As a rough 2026 range: a small 1.5kVA system with tubular batteries and a few panels lands around 1.5 to 2.5 million naira installed, a 3.5 to 5kVA home system with lithium runs roughly 4 to 8 million, and large homes with AC loads go well beyond that. Prices move with the exchange rate since most components are imported. The calculator shows an estimate range for your exact load; treat installer quotes as the final word.
Method: Inverter kVA = peak simultaneous load × 1.3 surge factor ÷ 0.8 power factor, rounded up to standard sizes. Battery bank = daily Wh × (backup hours ÷ 24) ÷ usable depth of discharge (lithium 80%, tubular 50%). Panels = daily Wh ÷ (5 peak sun hours × 75% efficiency) in 550W units. Component prices are rough estimates that move with the exchange rate. Confirm with installer quotes before buying.