Last reviewed: September 24, 2026
If you want to know whether the battery capacity on a solar quote is correct, do not accept a number such as “200Ah”, “10kWh” or “four batteries” without checking the battery voltage, chemistry, quantity, usable capacity and the backup load the installer used.
Quick answer: A battery quote is only verifiable when it identifies the exact battery model and shows enough information to calculate the storage. For tubular, GEL and AGM batteries, check Ah together with voltage. For lithium batteries, use the manufacturer’s verified kWh rating and usable capacity. Then compare that storage with the appliances and backup hours promised.
This matters in Nigeria because two installers can quote a “5kVA system” with very different battery banks. One may provide short backup for lights, fans and a TV. Another may include enough storage for a refrigerator, freezer, pump or longer overnight use. The inverter size alone does not tell you how long the system will run.
Start with the exact battery identity
Before checking the mathematics, make sure you know what the installer is actually quoting. The battery section should show:
- Brand and exact model number
- Battery chemistry: lithium, tubular, GEL, AGM or another type
- Nominal voltage
- Capacity in Ah, kWh or both
- Number of batteries
- Usable capacity or recommended depth of discharge
- Maximum continuous charge and discharge current
- Warranty, installation requirements and any battery-management-system requirements
“200Ah battery”, “200Ah lithium” or “large battery bank” is not enough information. Ask for the datasheet or a clear photograph of the battery label before paying a deposit.
Check the battery unit correctly
The correct comparison depends on the battery type.
Tubular, GEL and AGM batteries: check Ah and voltage
For lead-acid batteries, the quote will often use ampere-hours (Ah). Ah is not a complete energy figure unless the voltage is also known.
Use this simple nominal-energy calculation:
Nominal watt-hours = battery voltage × Ah
For example, one 12V 200Ah battery has approximately:
12V × 200Ah = 2,400Wh = 2.4kWh nominal energy
If four identical 12V 200Ah batteries are connected in series for an inverter that requires a 48V bank, the bank is approximately 48V 200Ah, not 48V 800Ah. Its nominal energy is:
48V × 200Ah = 9.6kWh nominal energy
Series connection raises voltage. Parallel connection generally raises Ah while keeping the voltage approximately the same. The installer must follow the battery and inverter manufacturer’s limits for both arrangements.
Lithium batteries: use verified kWh and usable capacity
Lithium batteries are commonly quoted in kWh, although the label may also show voltage and Ah. If the datasheet gives a verified energy rating, use that kWh figure as the main comparison.
For example, a battery labelled 51.2V 100Ah has approximately:
51.2V × 100Ah = 5,120Wh = 5.12kWh nominal energy
That does not automatically mean 5.12kWh will reach your appliances. The datasheet may specify a recommended usable percentage, reserve, discharge limit or usable-energy value. Use the manufacturer’s figure rather than assuming every lithium battery has the same usable capacity.
Nominal capacity is not the same as usable backup
A quote can be mathematically correct and still promise unrealistic backup if it treats nominal battery energy as fully available AC energy.
A practical planning check is:
Estimated AC energy available = nominal battery energy × usable fraction × inverter efficiency
Both the usable fraction and inverter efficiency are assumptions unless the exact equipment documentation gives more precise values. Battery chemistry, discharge rate, age, temperature, low-voltage cut-off and the inverter’s own consumption can change the result.
Worked example: checking a tubular-battery quote
Suppose a Nigerian home receives this line in a quote:
Four 12V 200Ah tubular batteries for a 48V inverter
First calculate the nominal energy:
48V × 200Ah = 9.6kWh nominal
For illustration only, suppose the design uses a 50% usable-energy assumption for the lead-acid bank and 90% inverter efficiency:
9.6kWh × 0.50 × 0.90 = 4.32kWh of estimated AC energy
If the backed-up load averages 600W, the simple runtime estimate would be:
4.32kWh ÷ 0.6kW = about 7.2 hours
This is not a guarantee. A refrigerator cycles rather than drawing its rated power continuously, a pump can have high starting demand, and battery capacity can change with the discharge rate and condition. The installer should show the actual load list and assumptions behind the promised runtime.
Worked example: checking a lithium-battery quote
Now suppose a quote includes two lithium batteries, each specified as 5.12kWh nominal, for a 48V-class inverter.
The total nominal energy is:
2 × 5.12kWh = 10.24kWh nominal
If the exact datasheet states 90% usable energy and the inverter is assumed to be 92% efficient, the illustrative AC energy estimate is:
10.24kWh × 0.90 × 0.92 = about 8.48kWh AC
At a steady 1,000W load, that would suggest roughly 8.5 hours before other practical limits are considered. If the quote promises a different result, ask the installer to explain whether the difference comes from the load profile, reserve setting, inverter consumption, battery temperature, BMS limits or a different usable-capacity assumption.
Do not copy the 90% assumption to every lithium battery. Use the exact model’s datasheet.
Check whether the battery can supply the inverter’s power
Capacity answers “how much energy can be stored?” It does not by itself answer “can the battery safely supply the load?”
For a rough DC-current check:
Battery current ≈ AC load ÷ (battery voltage × inverter efficiency)
For example, supplying a 4,000W AC load from a 48V battery at an illustrative 90% inverter efficiency would require approximately:
4,000W ÷ (48V × 0.90) ≈ 93A
The battery bank, cables, fuse or breaker and inverter must all be designed for the actual continuous and surge current. A battery can have enough kWh for a long runtime but still be unable to support a large simultaneous load if its discharge-current rating is too low.
This is especially important when the quote includes a refrigerator, freezer, borehole pump, pressing iron, microwave, air conditioner or other appliance with starting or heating demand.
Compare the quoted battery with the promised backup
Ask the installer to write down the assumptions instead of saying that the system will “last all night”. You need:
| Question | What the quote should show | Why it matters |
|---|---|---|
| What will run? | Appliance list and quantities | Runtime depends on the actual load, not inverter size alone. |
| How much power at once? | Running watts and starting/surge loads | The battery and inverter must supply the highest simultaneous demand. |
| How long? | Required backup hours and load profile | “Overnight” is not a precise duration. |
| Which battery? | Brand, model, chemistry, voltage and quantity | Ah, kWh, usable capacity and discharge limits vary by model. |
| What energy is usable? | DoD or manufacturer usable-energy figure | Nominal capacity is not the same as energy delivered to appliances. |
| What losses are included? | Inverter efficiency and standby consumption assumptions | DC battery energy is not delivered to the AC loads without losses. |
| What happens on cloudy days? | Charging and recovery plan | A battery may not return to full charge if solar input is insufficient. |
If the installer cannot show these assumptions, the battery number may be a sales estimate rather than a properly sized design.
Red flags on a battery quotation
- The quote says only “four batteries” without voltage, Ah, kWh or model.
- A lithium battery is compared with a tubular battery using Ah alone.
- The quote gives nominal kWh but says nothing about usable energy or reserve.
- The installer promises a fixed number of hours without listing the load.
- The battery voltage does not match the inverter’s required DC voltage.
- The bank’s maximum discharge current is lower than the expected inverter demand.
- Different battery brands, ages or models are mixed without documented compatibility.
- The installer refuses to provide a datasheet, serial-number record or warranty terms.
- The quote assumes panels will always recharge the battery fully, even during rain, heavy cloud or Harmattan conditions.
Use this five-step battery quote check
- Identify the battery. Record the exact model, chemistry, voltage, Ah/kWh rating and quantity.
- Calculate nominal energy. For an Ah battery bank, multiply the bank voltage by the bank Ah and convert Wh to kWh. For lithium, start with the manufacturer’s verified kWh rating.
- Apply usable-capacity and efficiency assumptions. Use the exact datasheet where available. Do not treat a general rule as a guarantee.
- Compare with the load. Multiply the expected load in watts by the required hours, then allow for inverter losses and appliance cycling.
- Check power and compatibility. Confirm battery discharge current, inverter voltage, BMS communication, series/parallel limits, cables and protection.
You can use the SolarPriceNG Battery Calculator to estimate the storage needed from your appliances and backup time. Treat the result as a planning check, then compare it with the exact battery and inverter documentation in the quote.
Example of a quote that needs correction
Imagine a quote says:
“5kVA inverter, 400Ah battery, 10 hours backup.”
This statement is incomplete. A careful buyer should ask:
- Is the battery bank 12V, 24V or 48V?
- Is it tubular, GEL, AGM or lithium?
- Is 400Ah the capacity of one battery or the complete bank?
- What is the nominal and usable kWh?
- Which appliances are included in the 10-hour promise?
- What happens when the refrigerator or pump starts?
- How much solar is installed, and can it recharge the battery after use?
Until those questions are answered, there is no reliable way to decide whether the battery capacity is correct.
What to request before approving the quote
- A complete appliance and critical-load schedule
- The exact inverter model and required battery voltage
- The exact battery model, chemistry, voltage, capacity and quantity
- The battery manufacturer’s usable-energy, DoD and discharge-current information
- The calculation showing expected backup time
- The panel size and expected charging or recovery plan
- Battery protection, cables, isolators, fuses or breakers and earthing scope
- Warranty, commissioning tests and handover documents
For a wider quotation review, read How to check whether a solar quote is overpriced or missing important parts in Nigeria. It covers the inverter, panels, protection and installation scope as well as the battery.
The bottom line
The battery capacity on a solar quote is probably not ready to trust if it is shown only as “200Ah”, “400Ah”, “10kWh” or “four batteries” without the exact model, voltage, chemistry, usable capacity and load calculation.
Check the battery in this order:
- Identity: exact model and chemistry
- Configuration: voltage, Ah/kWh and number of batteries
- Usable energy: manufacturer limits, reserve and inverter losses
- Power capability: continuous and surge discharge current
- Purpose: actual appliances, simultaneous load and required backup time
If the numbers do not line up, pause the purchase and ask for a revised itemised quote. Do not solve a sizing disagreement by bypassing protection, mixing incompatible batteries or changing wiring yourself. Battery-bank and inverter installation work should be designed, installed and tested by a competent professional.