For many three-bedroom homes, 3 kW is a reasonable essentials-only starting point, 5–6 kW commonly suits one carefully managed inverter AC plus household essentials, and 8 kW or more may be needed for broader comfort loads. The correct size comes from simultaneous watts and startup surge—not the number of rooms.
The points that change the decision
- List the exact appliances that may run at the same time.
- Calculate normal running demand separately from the largest motor-start surge.
- Add design headroom, but do not buy a huge inverter that the battery cannot support.
- Confirm single- or three-phase supply before selecting the final architecture.
Why bedroom count is only a starting clue
Two three-bedroom homes can have radically different power profiles. One may back up lights, fans, a refrigerator, television and router. Another may expect two air conditioners, a borehole pump, microwave and electric water heater to run during an outage. Those are different systems even though the floor plans sound identical.
The useful design question is: which loads can overlap? An inverter must carry that likely simultaneous load continuously and survive the most demanding credible startup event. Daily energy then determines how large the battery and solar array should be.
A five-step sizing method
Use product nameplates when available. Typical wattages are useful for early planning, but the installer should replace them with exact model data before procurement.
- 1
Build the load schedule
Record quantity, watts, hours per day and whether each appliance must remain powered during an outage.
- 2
Estimate simultaneity
Do not add every nameplate as if all equipment runs continuously; do include combinations the household genuinely expects.
- 3
Check motor surge
Refrigerators, pumps and non-inverter compressors can demand several times normal running current for a short period.
- 4
Add headroom
A preliminary design minimum can use roughly 20–25% running-load margin, while still checking the inverter's separate overload curve.
- 5
Verify the battery
Battery BMS continuous and peak discharge must support the inverter; enough kWh without enough kW can still trip the system.
Typical three-bedroom inverter tiers
These are planning bands, not product prescriptions. AC type, pump size, supply phase and load-management rules can move a home into a different tier.
| Use case | Typical simultaneous demand | Practical inverter starting point | What normally stays off |
|---|---|---|---|
| Essentials | 1.2–2.2 kW plus fridge/pump surge | 3 kW class | AC, water heating, cooker, iron |
| Everyday comfort | 2.5–4.5 kW with one managed inverter AC | 5–6 kW class | Multiple ACs and electric heating together |
| Broad home backup | 4.5–6.5 kW with selected heavy loads | 8 kW class | Load schedule still required |
| Whole-home / multiple AC | Above 6.5 kW or three-phase loads | 10–15 kW or engineered multi-unit bank | Depends on phase balancing and battery power |
Use the higher of the running-load-with-margin result and the verified surge requirement.
kW, kVA and surge are not interchangeable
Continuous output in kilowatts is the real-power capacity available to appliances. A kVA headline includes apparent power; where only kVA is quoted, the usable kW depends on the unit's rated power factor. For example, 5 kVA at 0.8 power factor is 4 kW—not 5 kW.
Surge should be read as power for a stated duration, not as a vague ‘two times’ marketing claim. A pump that needs high starting torque may require a soft starter, variable-frequency drive or different inverter architecture rather than simply more nominal capacity.
- Request the exact continuous output at expected temperature.
- Check overload power and duration in the manual.
- Confirm neutral, earthing and changeover arrangement.
- For three-phase homes, design phase allocation before ordering equipment.
A realistic essentials-plus-one-AC home
Assume lights, four fans, refrigerator, television/decoder, router, two laptops and one 1.5 HP inverter AC. A pump is allowed only when the AC is off.
Size my actual home
Choose a quick home profile or edit 80+ appliances, hours, surge, electricity band, phase and sunlight.
Primary sources used
Manufacturer and official Nigerian sources support technical or market claims. Worked examples remain SFP Technologies planning scenarios, not product guarantees.
Frequently asked questions
Can a 3 kVA inverter power a three-bedroom home?＋
It can power a carefully limited essentials circuit, but 3 kVA may provide materially less than 3 kW and may not start pumps or compressors. Check continuous kW, power factor, surge duration and the actual load schedule.
Can I run an air conditioner on a 5 kW inverter?＋
Often yes for one appropriately sized inverter AC alongside managed essentials, but verify its measured running input, startup behaviour, other simultaneous loads and battery discharge power.
Should I buy a larger inverter now for future expansion?＋
Allow sensible expansion headroom, but do not oversize the inverter without sizing battery current, cables, protection and charging sources for it. A modular platform can be safer than buying unused capacity.