Solar & Inverter Load Calculator — Fuel vs Solar Comparison
Two tools in one: calculate your exact inverter size, battery backup time, and solar panel requirements — then compare the monthly running cost of a generator against going solar.
Related Tools
Solar & Inverter Load Estimation
Inverter size, battery backup time & solar panel requirements
| Appliance | Watts (W) | Qty | Total |
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Generator Fuel Estimation
Estimate daily, monthly & annual generator running costs
Fuel vs Solar Monthly Cost Comparison
Compare generator, grid, and solar hybrid running costs side by side
Frequently Asked Questions
How do I size an inverter for my home?
Add up the wattage of all appliances you want to run simultaneously to get your total load. Multiply by 1.3 (30% safety margin) to get the minimum inverter VA rating. For example, a 500W total load needs at least a 650VA inverter — so you would buy the next standard size up, which is a 1000VA unit.
How long will my battery last during a power outage?
Battery backup time = (Battery Voltage × Battery Ah × Efficiency) ÷ Total Load in Watts. A 12V, 200Ah battery at 85% efficiency powering a 300W load lasts about 6.8 hours. Reducing your load (e.g. turning off the AC) significantly extends backup time.
How many solar panels do I need?
Divide your daily energy consumption (Wh) by the peak sunlight hours in your location to get total solar capacity needed. Then divide by your panel wattage to get the number of panels. Most of Africa gets 5–6 peak sun hours per day, Europe 3–4, and the Middle East 6–7.
Is solar cheaper than a generator in the long run?
Yes, in almost every case. While solar has a higher upfront cost (panels, inverter, batteries), the ongoing fuel cost of a generator compounds dramatically. A small petrol generator running 6 hours a day at ₦950/litre can cost over ₦130,000 per month. Solar operational costs are near zero after installation, typically paying back the investment within 2–5 years.
Solar vs Generator: How to Size Your Power System
Choosing between a generator and a solar-inverter system is one of the most important decisions for homes and small businesses experiencing frequent power outages. This tool helps you calculate both options precisely, so you can make a data-driven decision.
The Solar & Inverter section calculates your total electrical load by summing up all appliance wattages, then recommends a minimum inverter size with a 30% safety margin (e.g. 300W load needs at least a 390VA inverter, so you would pick a 500VA unit). Battery backup time is calculated using the formula: (Battery Voltage x Ah x Efficiency) / Total Load.
Solar panel sizing is based on your daily energy needs and the number of peak sunlight hours in your location — typically 4–6 hours per day in most of Africa, 3–5 in Europe, and 5–7 in the Middle East. Divide daily energy consumption (Wh) by peak sun hours to get the total solar capacity needed, then divide by your panel wattage to get the number of panels.
The Generator Fuel section uses the formula: Fuel Cost = Consumption Rate (L/hr) x Hours x Fuel Price. This gives you the true daily and monthly running cost of generator dependency — a cost that compounds enormously over a year.
The comparison section puts everything side by side: generator fuel cost, grid/PHCN electricity bill, and solar hybrid operational cost. While solar has a higher upfront investment, the monthly savings from eliminating fuel purchases typically lead to a full return on investment within 2–5 years.