If you have ever wondered how to size a solar inverter and battery bank for your home without overspending or under-buying, this guide will give you the exact method — plus a complete worked example you can follow with a pen and paper.
Buying a solar system in Nigeria usually goes wrong in one of two ways. Either you undersize it, and your inverter trips every time the fridge and the water pump start together, or you oversize it and spend ₦2 million on a battery bigger than you actually need. Both mistakes are expensive, and neither one is your installer’s fault if you never told them what you really run.
The good news: sizing a solar system is arithmetic, not guesswork. Once you understand five numbers — your wattage, your daily kWh, your surge load, your autonomy, and your peak sun hours — you can size any system in about 30 minutes, for any home, in any Nigerian city.
This guide walks through that entire process with a complete worked example of a real 3-bedroom family in Lagos. By the end you will be able to walk into any solar dealer, including ours, and ask for exactly what you need — and know whether their quote is fair.
Why Sizing Matters More Than Brand
A cheap inverter from an unknown brand and a premium one from Felicity or Victron can have the same wattage on the label and behave completely differently. The label tells you the maximum continuous output. It does not tell you whether the unit can sustain that output on a hot 38°C afternoon while also starting a compressor.
Three things decide whether a system actually performs:
- Correct sizing — the system matches the load and the local sun.
- Component quality — real lithium cells vs. relabelled prismatic cells, genuine MPPT control, honest warranty.
- Installation quality — cable sizing, protection devices, and earthing. This is the single biggest cause of system failure in Nigeria, and it is invisible in the product box.
Sizing is the part you control completely, and it is free. Get it right first, then worry about brands.
What You’ll Learn
- How to build a load list and calculate your daily energy use
- How inverter continuous rating and surge rating differ, and which one your fridge and pump need
- How to size a battery bank in kWh instead of guesswork, and why depth of discharge matters more than the number printed on the label
- Lithium vs. lead-acid: the honest comparison, including the 5 kWh battery fraud problem
- How many solar panels you need using real peak sun hours for Lagos, Abuja, Kano and Port Harcourt
- Charge controllers, DC cable sizing, breakers, fuses and earthing — the parts most installers skip
- A full worked example: a 3-bedroom home in Lagos, end to end
- What a system realistically costs, and 10 mistakes that ruin solar installations
Step 1: Build Your Load List
Every appliance has two numbers that matter: how much power it draws (watts) and how long you run it (hours per day). Multiply them to get watt-hours (Wh). Add up all the Wh and you have your daily energy consumption.
Start by walking through your home room by room and listing everything. Use the nameplate on the back of the appliance where you can — it is usually accurate. Where it is not, use the table below.
| Appliance | Typical running wattage | Typical hours/day | Daily energy (Wh) |
|---|---|---|---|
| LED bulb (9W) | 9 W | 6 | 54 |
| Ceiling fan | 60–80 W | 8 | ~560 |
| Refrigerator (single door) | 120–200 W | 10 | ~1,500 |
| Chest freezer | 150–250 W | 10 | ~2,000 |
| Television (43″) | 70–120 W | 6 | ~540 |
| Laptop | 45–65 W | 4 | ~220 |
| Router + decoder | 25 W | 18 | ~450 |
| Phone charging | 10–20 W | 3 | ~45 |
| Washing machine (per use) | 400–500 W | 1.5 × 3/week | ~215 avg |
| Electric iron (per use) | 800–1,200 W | 0.75 × 3/week | ~320 avg |
| Water pump (1 HP) | 550–750 W | 1 | ~650 |
| Air conditioner (1HP) | 900–1,100 W | 8 | ~8,000 |
A note on fridges and freezers: these do not run continuously. A fridge runs roughly 8–10 hours a day because the compressor cycles on and off. The table above already accounts for that. Do not multiply 24 hours by the wattage — it is the most common error beginners make, and it inflates your system by two or three times the size you need.
The one exception is air conditioning. An AC is a genuine daily load of 7–9 kWh and changes your entire system. If you plan to run AC on solar, say so now, because the system that handles a fridge and fans will not remotely handle an AC.
Step 2: Calculate Your Daily Energy (kWh)
Convert your total Wh into kilowatt-hours by dividing by 1,000.
Daily kWh = Total watt-hours ÷ 1,000
This single number — your daily energy requirement — is the foundation for sizing everything else: the battery bank, the panel array, and therefore the inverter.
Step 3: Size the Inverter (Continuous vs. Surge)
This is where most sizing errors happen, because people only look at one of two inverter ratings.
Continuous rating
The total of everything that can run at the same time. Your lights, fans, fridge, TV, laptop and charging all count. This is the number printed as “rated power” on the box.
Apply a 1.25 safety factor, because inverters should not be run at 100% of their rating continuously — that guarantees shortened life and heat problems.
Required continuous = Sum of all loads (W) × 1.25
Surge (peak) rating
Motors and compressors need a large momentary spike of current to start. The rule of thumb in Nigeria:
- Fridge and freezer compressor: 3–4× their running wattage, for a fraction of a second
- Water pump and motor: 3×
- Washing machine: 2×
Your inverter must be able to deliver its surge capacity for at least 5 seconds while carrying your continuous load at the same time. Cheap inverters advertise a surge number they cannot actually hold, which is why they trip and shut down on compressor start.
The scenario to test is: fridge and freezer starting while the water pump starts while you are watching TV and the fans are running. That is a realistic Nigerian evening.
| Appliance class | Continuous | Surge needed |
|---|---|---|
| Fridge 150 W | 150 W | 600 W |
| Freezer 200 W | 200 W | 800 W |
| 1 HP pump 750 W | 750 W | 2,250 W |
| Washing machine 500 W | 500 W | 1,000 W |
Add the continuous running loads (lights, fans, TV) to the largest single surge. If that total exceeds your inverter’s surge rating, upgrade the inverter before anything else.
Practical guidance for Nigerian homes:
- 1–2.5 kVA — small flat, fans, lights, TV, one fridge, no pump, no AC
- 3.6–5 kVA — the standard 3-bedroom family home with fridge, freezer, TV, washing machine and water pump. This is the most common size in Nigeria.
- 7.5–10 kVA — large family home, two freezers, multiple AC units, heavy cooking load
- 15 kVA and above — small business, clinic, salon with multiple ACs, workshop, or whole-building load
Step 4: Size the Battery Bank
This is the step where most systems go wrong, and it is the one that costs the most to fix later. A battery bank that is too small cannot carry the night; one that is too large simply ties up your capital in a box on the floor. Work through the three numbers below in order and you will land on a capacity that actually suits your load.
The battery bank is the most expensive part of your system, so this is where accuracy matters most. You will see batteries advertised in Ah (amp-hours), but for system design the useful unit is kWh (kilowatt-hours) — actual stored energy. Any seller who only quotes you Ah without converting to kWh is hiding something from you.
The three numbers you need
1. Depth of discharge (DoD)
The proportion of stored energy you can safely use before the battery needs recharging.
- Lithium (LiFePO4): 80–90%
- Lead-acid / tubular gel: 50%
This is why a 10 kWh lithium battery is roughly equivalent to a 20 kWh lead-acid battery for usable energy. Comparing the two on the “kWh” sticker alone is meaningless without it.
2. Autonomy (days of backup)
How many days you want to run without any sun. This is a lifestyle and budget decision:
- 0.5 day — hybrid, grid is reliable, solar just reduces your bill
- 1 day — the sensible default. Covers one full night plus a cloudy morning
- 1.5–2 days — essential for clinics, pharmacies, and homes in areas with long rainy-season outages
Every extra day of autonomy multiplies your battery cost. Nigeria has 2–4 months of the “raining season” with heavily reduced solar yield, so for a full off-grid home in the south, 1.5 days is more realistic than 1 day.
3. Round-trip efficiency
Energy is lost in the charge and discharge cycle: around 90–95% for lithium, 70–80% for lead-acid.
The formula
Required nominal energy (kWh) = Daily kWh × Autonomy days ÷ (Depth of discharge × Round-trip efficiency)
Then convert to amp-hours if you need it:
Amp-hours (Ah) = Nominal kWh × 1,000 ÷ Battery bank voltage (V)
Most Nigerian home systems run on a 24V or 48V bank. 48V is strongly preferred for anything above 3 kVA: lower current means thinner DC cable, less voltage drop, and far less power lost as heat in the cables.
Deep dive: lithium vs. lead-acid
| Factor | LiFePO4 (lithium) | Tubular gel / lead-acid |
|---|---|---|
| Usable energy | 80–90% | ~50% |
| Round-trip efficiency | 90–95% | 70–80% |
| Cycle life @ 80% DoD | 3,000–6,000 cycles | 500–1,000 cycles |
| Usable life (real world) | 8–12 years | 2–4 years |
| Performance in heat | Very good, still charges at 45°C+ | Loses significant life above 35°C |
| Maintenance | None | Frequent water top-ups, terminal cleaning |
| Weight | Light | Very heavy |
| Upfront cost | High | Low |
| Cost per kWh over life | Low | High |
The honest truth about cost: a lead-acid bank is roughly 40–50% cheaper upfront, but because you can only use half of it and it lasts a third as long, its cost per usable kWh over 10 years is usually higher than lithium — before you count the diesel or generator fuel you burn when the lead-acid bank cannot hold enough charge to carry the night.
The battery fraud problem. The Nigerian market is flooded with lithium batteries advertised as 10 kWh, 12 kWh and 15 kWh that are in fact far smaller — relabelled prismatic cells with a false capacity sticker. There is a simple way to check what you are buying:
- Weigh the battery. A true 10 kWh LiFePO4 at 48V weighs roughly 85–95 kg. A 5 kWh battery weighs about half that. If the weight matches a smaller battery, the label is a lie.
- Ask for the cell specification (Ah and nominal voltage) and compute Ah × V ÷ 1,000. For example a 200 Ah, 3.2 V cell × 15 cells in series × 4 in parallel = 48 V at 200 Ah = 9.6 kWh.
- Confirm the warranty in writing, with a physical return address in Lagos rather than a generic email address.
Step 5: Size the Solar Panel Array
Your battery needs to be refilled every day, so your panels must generate at least your daily kWh — plus losses.
Array size (kWp) = Daily kWh ÷ (Peak sun hours × System efficiency)
Use a system efficiency of 0.75 to be realistic. This accounts for heat losses in the panels, dust, wiring losses, and the fact that panels never produce their full nameplate rating in real conditions. Using the nameplate 1,000 W figure directly is the second most common sizing error in Nigeria, and it results in a system that chronically runs out of power by February.
Peak sun hours in Nigerian cities
This is a real geographic advantage. Nigeria receives 3.5–6.0 peak sun hours per day depending on region, which puts it in the top tier globally for solar yield.
| Location | Typical peak sun hours | Planning recommendation |
|---|---|---|
| Kano, Sokoto, Katsina | 5.5–6.0 | Use 5.0 for safety |
| Abuja, Jos, Makurdi | 5.0–5.5 | Use 4.5 for safety |
| Ibadan, Akure, Benin City | 4.5–5.0 | Use 4.0 for safety |
| Lagos, Abeokuta | 4.0–4.5 | Use 3.5 for safety |
| Enugu, Awka, Onitsha | 4.0–4.5 | Use 3.5 for safety |
| Port Harcourt, Warri | 3.5–4.0 | Use 3.0 for safety |
Note on Lagos: heavy cloud cover and heavy atmospheric pollution during the rainy season reduce output significantly, and dust in the Harmattan season knocks down a further 10–15% if panels are not cleaned. Using 3.5 for Lagos is not pessimistic, it is realistic.
Panel sizing rules of thumb
- 1 kW of array supports roughly 4–5 kWh of daily consumption in southern Nigeria
- A 700W panel produces about 2.8 kWh per day in Lagos (700 × 3.5 × 0.75 ≈ 1,840 Wh… realistically 2.0–2.4 kWh after full derating). Always ask the installer for the expected daily yield, not the nameplate.
- For a home using 10 kWh/day in Lagos, you need roughly 3–4 kWp, which is 4–6 panels of 700W
- Orient panels north or south in Nigeria (equator), tilted 10–15° to shed rain and dust. Avoid flat-roof mounts with no tilt — they lose 15–20%.
Step 6: Charge Controller, Cables and Protection
This is the part that separates a system that lasts 10 years from one that fails in 18 months. Most of these components cost very little relative to the battery and inverter, and skipping them is false economy.
MPPT charge controller
If your inverter does not have a built-in MPPT solar charger — and most do not — you need a separate controller. Size it by array current, not array wattage:
Controller rating (A) ≥ Array watts ÷ Panel Vmp × 1.25
A 2,800 W array at 41 V Vmp draws about 68 A, so you need at least an 85 A MPPT controller. Never run panels directly into a battery without one — the battery will be overcharged and destroyed.
DC cable sizing
This is the number one cause of “my inverter shows low battery” complaints. DC current is high, and undersized cable causes voltage drop, wasted energy as heat, and melted insulation.
| Inverter size | Minimum DC cable | AC cable |
|---|---|---|
| 1–2.5 kVA | 16 mm² | 2.5 mm² |
| 3–5 kVA | 25–35 mm² | 4–6 mm² |
| 5–10 kVA | 50–70 mm² | 10 mm² |
| 10–15 kVA | 95 mm² | 16 mm² |
Use genuine copper cable. In Nigeria, “half-cut” copper-cored cable is extremely common in the market and is a fire risk. Verify the copper content with a magnet and a weight check, or buy from a reputable supplier. Undersized DC cable on a 5 kVA system wastes 5–10% of your energy as pure heat.
Protection devices — all mandatory
- DC disconnect switch — lets you isolate panels for maintenance
- DC fuse or breaker — protects the cable run from panel faults
- AC breaker — required between inverter and your distribution board
- Surge protection (SPD) — critical in Nigeria’s lightning-prone climate
- Proper earthing — rods, proper bonding, and correct connections. Un-earthing systems are a leading cause of inverter failure in Nigeria
- Isolators for all battery connections — lithium batteries can deliver lethal current; isolate before any maintenance
Worked Example: A 3-Bedroom Home in Lagos
Let’s size a real system. A family of five in a 3-bedroom flat in Lagos with: 8 LED bulbs, 3 ceiling fans, 1 fridge, 1 chest freezer, 1 TV with decoder, 1 router, 1 laptop, regular phone charging, a washing machine 3× a week, an iron 3× a week, and a 1 HP water pump for 1 hour daily. They want to run everything except air conditioning, and they want 1 day of autonomy with the grid as backup.
1. Daily energy
| Load | Watts | Hours | Daily Wh |
|---|---|---|---|
| 8 × LED bulbs | 72 | 6 | 432 |
| 3 × ceiling fans | 225 | 8 | 1,800 |
| Fridge | 150 | 10 | 1,500 |
| Chest freezer | 200 | 10 | 2,000 |
| TV + decoder | 100 | 6 | 600 |
| Router | 15 | 18 | 270 |
| Laptop | 65 | 4 | 260 |
| Phone charging | 15 | 3 | 45 |
| Washing machine (avg) | 500 | — | 214 |
| Iron (avg) | 1,000 | — | 321 |
| Water pump | 750 | 1 | 750 |
Total = 8,192 Wh ≈ 8.2 kWh per day
2. Inverter
Continuous load (everything that can run at once) = 72 + 225 + 150 + 200 + 100 + 15 + 65 + 15 + 500 + 1,000 + 750 = 3,092 W
With 1.25 safety factor: 3,092 × 1.25 = 3,865 W
Surge check — worst realistic evening: freezer surge (800) + pump surge (2,250) + running lights/fans/TV (400) = 3,450 W surge, while carrying ~2,000 W continuous.
Recommendation: a 5 kVA / 5 kW hybrid inverter with at least 10 kVA surge capacity. This is the standard size for a Lagos family home, and it leaves headroom if you add an appliance later.
3. Battery bank
Daily 8.2 kWh × 1 day autonomy ÷ (0.85 DoD × 0.93 efficiency) = 8.2 ÷ 0.79 = 10.4 kWh nominal
Round up to 12 kWh at 48V (= 250 Ah). A 12 kWh lithium battery is the right fit, and it is the most common single purchase for a Lagos family home.
If this family wanted to survive a two-week NEPA outage with no sun, they would need 2 batteries (24 kWh) — that is roughly double the battery cost, and worth it only if blackouts are genuinely frequent for them.
4. Solar array
8.2 kWh ÷ (3.5 peak sun hours × 0.75 efficiency) = 3.1 kWp
Recommendation: 4–5 × 700W panels (2.8–3.5 kWp). Five panels gives margin for Lagos’s cloudy season and for dusty panels in the Harmattan.
5. Controller and protection
Array 3,500 W ÷ 41 V Vmp = 85 A, × 1.25 = 107 A MPPT. If the inverter has a built-in MPPT solar input, no separate controller is needed — confirm before buying.
Protection: DC disconnect, DC breaker, AC breaker, SPD, and proper earthing. DC cable 35 mm², AC cable 6 mm².
The finished specification
| Component | Specification |
|---|---|
| Inverter | 5 kVA / 5 kW hybrid, 48 V, ≥10 kVA surge |
| Battery | 12 kWh LiFePO4, 48 V (250 Ah) |
| Panels | 4–5 × 700 W monocrystalline (2.8–3.5 kWp) |
| Charge controller | 100–120 A MPPT (if not built into inverter) |
| DC cable | 35 mm² genuine copper |
| AC cable | 6 mm² |
| Protection | DC isolator, DC breaker, AC breaker, SPD, earthing |
| Design daily yield | ~8–9 kWh, matching the 8.2 kWh requirement |
What This System Costs
Prices in Nigeria move constantly, so treat the following as indicative ranges to help you sanity-check a quote — not as a price list. Confirm current pricing before you buy.
| Item | Indicative range (₦) |
|---|---|
| 5 kVA hybrid inverter | 450,000 – 1,100,000 |
| 12 kWh LiFePO4 battery | 1,700,000 – 2,600,000 |
| 4–5 × 700 W panels + mounting | 600,000 – 900,000 |
| MPPT controller (if required) | 180,000 – 450,000 |
| Cables, breakers, SPD, earthing | 200,000 – 450,000 |
| Installation labour | 150,000 – 400,000 |
| Total (lithium) | 3,300,000 – 5,900,000 |
Now compare that against the running cost. A petrol or diesel generator burns roughly 10.5 kWh per litre and costs several times more per kWh than your solar system once fuel, oil, servicing and downtime are counted. For a household using 8 kWh/day, solar typically pays back its capital cost within 2–4 years, and the running cost after that is close to zero.
Ask any reputable installer for a written quote with model numbers and warranty terms. If a quote cannot be itemised like the table above, it is not a quote.
10 Mistakes That Ruin Solar Systems in Nigeria
- Ignoring surge rating. The most common cause of inverter trips and shutdowns. Inverters that advertise a surge figure they cannot sustain for 5 seconds are not worth the price difference.
- Undersized DC cable. Causes voltage drop, “battery full” readings that are not true, wasted energy, and eventually cable fires. Never reuse existing house wiring as the DC run.
- Running panels without an MPPT controller. Destroys the batteries. Confirm your inverter has a built-in MPPT solar input if you are not buying a separate controller.
- No surge protection in a lightning-prone country. One direct strike without an SPD can write off the entire system.
- Skipping earthing. Improper or absent earthing is among the top causes of inverter failure and shock risk in Nigeria.
- Buying “kWh” on trust. Verify lithium capacity by weight and cell specification. The mislabelled battery market is large.
- No maintenance plan. Panels need cleaning, battery terminals need checking, and fans need clearing from dust. A 15-minute check every 3 months prevents most failures.
- Oversizing for AC, then undersizing everything else. Adding a 1.5 HP AC to a system sized for lights and a fridge is the most common reason systems “suddenly stop working.”
- No surge capacity margin for future loads. If your inverter is running at 90% of its rating, you have no room for anything new.
- Buying during a “free battery” promo and losing warranty. Promotions that bundle cheap batteries with inverter purchases often void the inverter warranty, and you end up replacing the battery within 18 months anyway.
Maintenance Schedule
| Interval | Task |
|---|---|
| Weekly (2 min) | Check the inverter display for fault codes and the state-of-charge reading |
| Monthly | Clean panels with water and a soft cloth, early morning or evening |
| Every 3 months | Check battery terminals for corrosion, tighten connections, clear dust from inverter and controller fans |
| Every 6 months | Verify earthing continuity and test all breakers and the SPD |
| Yearly | Test battery capacity and confirm the inverter firmware is current |
For lead-acid systems, add a monthly water top-up and a terminal-cleaning routine. For lithium, maintenance is essentially nil — a major practical reason to prefer it in Nigeria’s heat.
Frequently Asked Questions
How do I know what size inverter I need?
Add the wattage of every appliance that can run at the same time, then multiply by 1.25. For example, a Lagos family home totalling about 3,100 W of simultaneous load needs roughly 3,900 W, so a 5 kVA inverter is the right choice.
How many solar panels do I need for a 3-bedroom apartment?
For a 3-bedroom home using about 8 kWh per day in Lagos, you need roughly 3–4 kWp, which is 4–5 × 700 W panels. In Kano or Abuja you would need fewer because those cities get more sun.
How long does a 12 kWh lithium battery last?
On a 12 kWh battery at 85% depth of discharge, a family consuming 8 kWh per day gets about 1.2 days of backup. With a 3,000-cycle battery used once per day, expect 8+ years of service life.
Is lithium or lead-acid better in Nigeria?
Lithium, for almost every Nigerian household. It uses 80–90% of its capacity versus 50% for lead-acid, lasts 3–6 times longer, tolerates Nigerian heat far better, needs no maintenance, and despite a higher upfront price works out cheaper per kWh over its life. Lead-acid only makes financial sense for a minimal, occasional backup system.
Do I need a separate solar charge controller?
Only if your inverter does not have a built-in MPPT solar input. Many hybrid inverters do not. If yours does, that function is built in and a separate controller is both unnecessary and a waste of money. Confirm the specification before buying either.
Can I run an air conditioner on solar?
Yes, but it changes the system completely. A 1 HP AC uses about 8 kWh per day — roughly the entire daily consumption of a typical family home. Running one AC daily means a 3–5 kWp array and a 15–20 kWh battery bank, at roughly triple the cost. It is possible and increasingly common; it is simply a different and much larger project.
How many batteries can I connect together?
Always confirm the manufacturer’s maximum configuration. Common limits are 4 batteries in parallel for 48 V lithium banks, and mixing batteries of different capacities, ages or brands is one of the fastest ways to damage a bank. If you need more capacity, add a parallel bank rather than mixing within one.
What size inverter do I need to run a water pump and fridge?
A 1 HP water pump needs 750 W continuous and up to 2,250 W to start. A fridge needs 150 W continuous and 600 W to start. Run together with lights and fans, a 3.6 kVA inverter handles it; a 5 kVA gives comfortable headroom.
Is a hybrid inverter better than a pure off-grid inverter?
For most Nigerian homes, yes. A hybrid inverter charges from solar, runs from the battery, and passes grid power through when solar is insufficient. It gives you the resilience of off-grid with the safety net of the grid — and you can expand the battery bank later without changing the inverter.
Why is my system showing “low battery” when the battery is new?
Four usual causes: the DC cable is undersized causing voltage drop; the charge current is too low to replace what you consume; the panels are undersized for your actual load; or the battery is not actually new and not being fully charged. Check cable sizing and system design first — a new battery rarely fixes an undersized array.
This guide covers the complete method. If you want to go further on any single part, these are the detailed write-ups:
- Solar Inverter vs Generator in Nigeria — the real cost per kWh over ten years, with a worked payback calculation for a Lagos household.
- Lithium vs Lead-Acid Batteries — usable capacity, cycle life, heat performance, and the four checks that expose a counterfeit “kWh” rating.
- How Many Solar Panels Do I Need? — peak sun hours for Nigerian cities and the exact arithmetic for six household sizes.
- Can You Run an Air Conditioner on Solar? — why one AC roughly doubles your whole system, and how to size for it.
- Installation Wiring, Protection and Safety — DC cable sizing, the six mandatory protection devices, and the commissioning checklist to demand before handover.
Final Checklist Before You Buy
- Your daily kWh is calculated from a real load list, not a guess
- Inverter continuous rating = your peak simultaneous load × 1.25
- Inverter surge rating covers your worst compressor start scenario
- Battery capacity = daily kWh × autonomy ÷ (DoD × efficiency), in kWh not just Ah
- Battery verified by weight and cell specification
- Array sized using your city’s real peak sun hours with 0.75 efficiency, not nameplate ratings
- MPPT controller present, or built into the inverter
- DC cable sized for the inverter output, genuine copper
- Breakers, DC isolator, SPD and earthing all included in the quote
- Written warranty with a physical Lagos address
If you are still unsure, bring us your appliance list and we will size the system with you — no obligation, and we will tell you if what you need is smaller than what you were quoted elsewhere.
Related reading: our guide to lithium batteries, power inverters, and solar panels.
Sources and Further Reading
For verified irradiance and peak sun hours for your specific location rather than a national average, the Global Solar Atlas is the authoritative public dataset.
Frequently Asked Questions on Battery Bank Sizing
How big should my battery bank be?
Size it from two numbers: your daily consumption in kWh, and the number of days you want to carry without sun. Multiply them, then divide by depth of discharge. A battery bank that is too small cannot carry the night, which is why this is the calculation most worth doing carefully.
Should I buy one large battery bank or several smaller ones?
Several smaller units in parallel are usually the better answer. A battery bank built from two or three matching batteries is easier to replace, cheaper to replace individually, and can be expanded later without changing anything else in the system.
Can I add more capacity to my battery bank later?
Yes, provided the additions match the existing bank in voltage, chemistry and age. Adding capacity in parallel is straightforward. Changing the bank voltage later is not, which is the reason to choose 48V from the start if you expect to grow.
How long does a battery bank last?
Chemistry, depth of discharge and heat decide it. A quality lithium bank used once a day should give 8 to 15 years; a lead-acid bank in a hot climate may manage two to four.
Is a bigger battery bank always better?
No. Beyond sensible autonomy, extra capacity sits unused and ties up capital. Find the size that covers your worst realistic night plus a margin, and stop there.
How much does a battery bank cost?
Lithium is roughly two to three times the upfront cost of lead-acid, but gives more usable capacity and lasts several times longer, so cost per usable kWh over its life is usually lower.
Do I need to know anything about battery bank chemistry before quoting?
Yes, and it changes the price more than anything else. Lithium and lead-acid at the same amp-hour rating are entirely different products, and a battery bank quoted by Ah without naming the chemistry has not been specified at all.
What is a reasonable battery bank warranty?
Look for a stated cycle life rather than just a year count. A quality lithium bank should be warrantied for 3,000 or more cycles at a stated depth of discharge. A battery bank warranted only in years, with no cycle figure, tells you very little.
Key Takeaways on Sizing a Battery Bank
- Size a battery bank from two numbers: daily consumption in kWh, and the days of autonomy you want. Everything else is arithmetic.
- A battery bank is sized in kWh, not in amp-hours. A 500 Ah bank at 24V and a 250 Ah bank at 48V hold the same energy.
- Depth of discharge is the number sellers omit: lithium gives you 80-90% usable, lead-acid about 50%.
- Going from 24V to 48V halves the current, which quarters the cable loss and often saves enough on copper to pay for itself.
- Every extra day of autonomy multiplies the cost of the battery bank. One day is the sensible default for most homes.
- A battery bank that cannot carry the night is the single most common reason a system feels like it never works.
Read Next
- 24V vs 48V Solar Systems — the bank voltage decision that drives cable size, losses and expandability.
- Solar Panel Technology Explained — mono, poly, half-cut, TOPCon and bifacial, and which performs best in Nigerian heat.
- Solar Inverter Security — securing smart inverters, monitoring accounts and your solar business data.
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