Solar Calculator for Lagos — Size It From Your Load
Daily kWh → panels, battery, inverter · 4.5 peak sun hours · costs from live component data
Most Lagos solar quotes start from the wrong end — the installer asks your budget, then sizes a system to it. That is backwards. Sizing starts with your load: what you actually run, for how many hours, and how much of it must survive a blackout. Work that out first and you can judge any quote in about a minute.
Size your system from your load
Set how many of each you run and for how many hours a day.
Sizing assumes Lagos's 4.5 average peak sun hours, 25% system losses and 85% usable depth of discharge on lithium. Costs are equipment only — labour and balance of system typically add 10–20% on top. This is a planning estimate to check a quote against, not a quote.
Start with your daily kWh, not your budget
Add up each appliance's wattage multiplied by the hours you run it per day, then divide by 1,000. A 150W fridge running 24 hours is 3.6kWh. Six 10W bulbs for six hours is 0.36kWh. A 1,000W pressing iron for 20 minutes is 0.33kWh. Most Lagos flats that are not running air conditioning land between 3kWh and 8kWh a day; add a single 1.5HP AC unit running six hours and you add roughly 6kWh on its own.
That daily kWh figure is the one number every honest installer will ask for. If a quote arrives without anyone asking what you run, the system was sized to your wallet rather than your house — and it will either be oversized (you overpaid) or undersized (it cuts out at night, which is exactly when you wanted it).
Panels are sized by sun hours, not by wattage alone
Lagos averages about 4.5 peak sun hours a day. That is the number that turns a panel rating into real energy: a 450W panel does not make 450W all day, it makes roughly 450W × 4.5 hours ≈ 2kWh on a good day, and meaningfully less in the July–September rains. To cover a 6kWh daily load you therefore need roughly 6 ÷ 2 = 3 panels of headroom in theory, and in practice 4–5 once you allow for cloud, dust on the glass, and charging losses.
This is why panel count is the part of a quote most worth checking. Undersizing the array is the cheapest way for an installer to hit an attractive price, and it is invisible until the first cloudy week, when the battery stops reaching full charge and the system quietly starts leaning on the grid.
The battery decides what a blackout feels like
Panels only work while the sun is up, so every hour of night-time backup comes out of the battery. Size it by the load you need after dark, not your total daily load — for most homes that is the fridge, fans, lights, phones and the router, which is a far smaller number than the daytime peak. Then add headroom: lithium (LiFePO4) batteries are usually specified to about 80–90% usable depth of discharge, while tubular lead-acid should not go below about 50% if you want it to last its rated years.
That depth-of-discharge difference is why a 5kWh lithium unit and a 5kWh tubular bank are not the same purchase. The lithium gives you roughly 4–4.5kWh you can actually use; the tubular gives you about 2.5kWh before you start shortening its life. Compare usable kWh, not nameplate kWh, or the cheaper bank will look like better value than it is.
Tier prices are fully installed — panels, inverter, battery and labour together.
Price per watt across sizes, with the source and verification date for each.