Solar & Power · EuroVista Insights

How to Size a Solar System for a Nigerian Office

Published 7 May 2026 · 8 min read · by EuroVista team

Getting solar sizing wrong is expensive in both directions — an undersized battery bank drains by 3 am; an oversized array wastes capital that could fund another site. This guide walks through the five steps EuroVista uses to size hybrid solar systems for Nigerian offices, schools, and institutions, with a worked example at the end.

Step 1: List and measure your critical loads

Critical loads are the appliances that must stay on during a grid outage. For most Nigerian offices that means lighting, ceiling fans, computers, a server or NAS, CCTV, a router, and phone chargers. Air conditioning is usually excluded from the critical load list for budget reasons — a 1.5 HP split unit alone draws 1,100–1,300 W continuously, which would more than double the required battery and panel capacity.

To build your load list, check the watt rating printed on each device's label or power brick. If the label is missing, use these typical values:

For each appliance, also note how many hours per day it typically runs during a working day. That figure is your runtime, and you will use it in the next step.

Step 2: Calculate daily Wh and apply the dirty-power buffer

Multiply each appliance's wattage by its daily runtime to get its watt-hours per day, then add all appliances together for your raw daily total.

In Nigeria, that raw total is not the number to size from. The national grid delivers voltage that routinely sags to 160–180 V or spikes to 250–270 V, and generators introduce harmonic distortion. These conditions create resistive heat in motor windings, transformer cores, and switch-mode power supplies — heat that represents real energy consumption not captured by the nameplate wattage. Add a 20–25% dirty-power buffer on top of the raw total to account for this.

Step 3: Size the battery bank

Two battery chemistries dominate in Nigeria: tubular lead-acid (OPzS flooded or OPzV gel) and lithium iron phosphate (LiFePO4). Their usable depth of discharge (DoD) differs significantly and directly affects the Ah capacity you must buy.

Temperature derating is critical in Nigeria. A nominally rated 100 Ah tubular battery operating at 35 °C ambient delivers roughly 90 Ah; at 40 °C — a common internal temperature in a hot equipment room in Kano or Maiduguri — that drops to approximately 80 Ah. Always apply a 10–15% ambient temperature derate when sizing lead-acid banks. LiFePO4 is less affected but should still be derated 5–8% above 40 °C.

For days of autonomy: most Nigerian offices that receive 6–8 hours of grid per day can work with 1 day of autonomy — the battery carries the overnight and early-morning load, and solar or grid recharges it by midday. Remote sites, clinics, or sites with fewer than 4 hours of grid per day should target 1.5–2 days of autonomy. Multiply your daily Wh by the autonomy days before applying the formula.

Step 4: Size the solar array

Solar array output depends on how many peak sun hours (PSH) your site receives. PSH is the equivalent number of hours per day at 1,000 W/m² — the Standard Test Condition (STC) irradiance at which panel ratings are measured. Nigeria varies considerably by region and season:

Real-world panel output is typically 75–80% of the STC rating because of operating temperature (panels heat up to 60–70 °C on a typical Nigerian roof), dust accumulation, module mismatch, and wiring losses. Use 0.75 as your derate factor for conservative sizing.

For hybrid systems, size so that the solar array can produce 1.5× the daily load under average conditions. The extra capacity charges the battery bank faster on good days and provides a buffer against two or three consecutive overcast days without running the generator.

Step 5: Choose the right inverter or charger type

The inverter/charger is the heart of the system — it determines how solar, grid, battery, and loads interact. Three configurations are relevant for Nigerian offices:

Hybrid inverter (grid + solar + battery)

Right for most Nigerian offices. It prioritises solar, supplements from the grid when solar output is insufficient, charges batteries from grid or solar, and switches to battery the instant the grid fails — zero transfer time. When the grid is unstable, the inverter isolates from it and runs in island mode. This is the configuration EuroVista specifies for the majority of office, school, and institutional deployments.

Pure off-grid inverter

The correct choice for sites with no grid connection at all, or where grid reliability is so poor that the grid contributes less than an hour per day on average. Without grid charging as a backup, the battery and panel sizing must be more conservative — generally 2 days of autonomy and a larger array.

Online double-conversion UPS

Best for server rooms, medical equipment, and any load that cannot tolerate even a 20 ms transfer gap. The load always runs from a regulated inverter output — voltage and frequency remain perfectly stable regardless of grid quality. This type is often combined with a separate hybrid system: the hybrid powers the building, the double-conversion UPS conditions power to the server room from the hybrid's output.

Worked example: 10-person office in Lagos

Below is a complete sizing walkthrough for a typical 10-person Lagos office with critical loads only — no air conditioning on the solar circuit.

Load table

Sizing calculations

1. Dirty-power buffer: 11,550 Wh × 1.22 = 14,091 Wh/day (round up to 14,100 Wh)
2. Battery bank — LiFePO4 at 48 V system, 80% DoD, 1 day autonomy: 14,100 ÷ 48 ÷ 0.80 = 367.2 Ah. Specify a 400 Ah, 48 V LiFePO4 bank.
3. Solar array — Lagos PSH = 4.5 h, derate 0.75: 14,100 ÷ 4.5 ÷ 0.75 = 4,177 Wp. Specify 4.5 kWp (e.g., 12 × 400 W monocrystalline panels) to include the 1.5× buffer built in.
4. Hybrid inverter: Peak simultaneous load is roughly 4 kW (lights + fans + all laptops + always-on loads). Specify a 5 kW continuous / 10 kW surge hybrid inverter.

Common questions

What is the difference between kVA and kW?

kVA is apparent power; kW is real power. For purely resistive loads like heaters and incandescent bulbs, kVA and kW are equal. For motors, electronic drives, and switch-mode power supplies, kVA is higher than kW by the power factor — typically 0.7–0.9 for office equipment. Always spec your inverter in kW continuous output, not kVA, and confirm the manufacturer's power factor assumption. A "5 kVA inverter" rated at 0.8 PF delivers only 4 kW of real power to your loads.

Why does my battery drain before morning?

The two most common causes are undersizing and an incorrect DoD cutoff setting. First, recalculate your actual daily load — loads added after the initial sizing are a frequent culprit. Second, check the inverter's low-battery cutoff voltage: for a 48 V LiFePO4 bank, cutoff should be around 47.2–48.0 V (20% state of charge); for tubular lead-acid, around 46.8 V (50% DoD). If the cutoff is set too low, you are drawing the battery deeper than its rated DoD, which both drains it faster tonight and shortens its life over hundreds of cycles.

Can I add more solar panels later?

Yes, as long as the MPPT charge controller has remaining input headroom. When specifying the MPPT, always choose a unit rated for at least 1.25× your planned initial panel capacity. This leaves room to add a string or two without replacing the controller. Also confirm the open-circuit voltage (Voc) of your planned expanded array does not exceed the controller's maximum input voltage — a common mistake when panels are added in series rather than parallel.

Do I need a battery management system (BMS)?

A BMS is mandatory for LiFePO4 — there are no exceptions. Without one, individual cells can overcharge or over-discharge, leading to permanent capacity loss or, in worst cases, thermal runaway. Reputable LiFePO4 packs ship with an integrated BMS that communicates with the inverter via CAN bus or RS485, allowing the inverter to respect charge limits automatically. If a supplier offers LiFePO4 cells without a BMS, or cannot demonstrate BMS communication with your inverter model, do not proceed.