System Sizer
Go from load to a full engineered recommendation.
Free to use without an account. A free installer account adds saved work, A4 previews and branded PDF exports.
The system sizer converts a load profile into an engineered recommendation: inverter size in kVA, usable and nominal battery capacity, solar array size, panel count, expected daily generation and backup hours at your night load.
How the System Sizer works
Start from a real load
Import the result from the Load Calculator or type daily and night kWh directly. Battery sizing follows night kWh; array sizing follows total daily kWh.
Set the design parameters
Choose lithium or lead-acid, confirm depth of discharge, peak sun hours, system losses and any planned expansion. Defaults are deliberately conservative.
Review the warnings
The sizer flags high surge, a panel count well above the calculated array, unsafe 12 V designs and large daily loads that need load staggering or three-phase equipment.
Worked example
A home with two inverter air conditioners
3,700 W running load, 8,900 W surge, 21.8 kWh per day and 20.3 kWh at night, with 4.5 peak sun hours, lithium at 90% depth of discharge and 580 W panels.
- 5 kVA inverter
- About 26 kWh nominal lithium bank (roughly 530 Ah at 48 V)
- 12 × 580 W panels, about 7 kWp
- Around 23 kWh expected generation per day
Assumptions and limits
- Peak sun hours default to 4.5. Most of Nigeria sits around 4–6, and the rainy season is lower.
- System losses of 0.75 cover wiring, temperature, dust, inverter and battery losses. Do not raise this to make a design look better.
- The result is a design starting point, not a quotation. Confirm inverter surge ratings, MPPT limits and roof space before ordering.
Frequently asked questions
What does the system sizer calculate?
It recommends inverter kVA, battery nominal and usable capacity, array kWp, panel count, expected daily generation and backup hours at your night load.
Which battery chemistry should I choose?
Choose lithium for a lower depth of discharge and longer cycle life, or lead-acid when that is the available or preferred option. The calculator adjusts usable capacity and efficiency.
Does the sizer include cable and protection sizing?
No. Use the Cable and Protection Sizing tool for breakers, surge protection and voltage drop after the main system is sized.
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Last updated 17 October 2026Maintained by Mishka Energy.
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