Solar sizing guide
How to Size a Solar System for Your Home in Nigeria
A practical guide to estimating appliance loads, daily energy use, inverter demand, battery storage and solar-panel capacity before requesting a final system design.
A useful solar-system estimate starts with the appliances you want to run, not with a package name alone. Two homes can own similar appliances but need different systems because their operating hours, simultaneous use and desired backup time are different.
The steps below help you prepare a realistic load list and understand the decisions behind a solar quotation. They are a planning guide rather than a final engineering design: site conditions, actual equipment ratings and product-specific limits still need to be checked.
1. List the appliances the system must power
Write down every appliance that you expect to use during an outage or from solar energy. Separate essential loads—such as lighting, fans, internet equipment and a refrigerator—from optional high-demand loads such as air conditioners, electric kettles, irons, pumps and cooking appliances.
Use the rating plate, manual or manufacturer information for each appliance where possible. A generic estimate can help with early planning, but the rating on the actual appliance is a better basis for a quotation.
- Record the appliance name and rated watts.
- Record how many of each appliance will run.
- Estimate the hours of use in a typical day.
- Mark appliances likely to run at the same time.
- Identify motors, compressors and pumps that may need extra starting power.
2. Calculate daily energy in watt-hours
Power and energy are related but different. Watts describe the power an appliance needs at a moment in time. Watt-hours estimate how much energy it uses over a period. Multiply watts by quantity and daily operating hours for each load, then add the results.
For example, a 10-watt lamp used for five hours represents 50 watt-hours of daily energy. Real consumption can vary because some appliances cycle on and off, change operating modes or draw different power under different conditions.
3. Check simultaneous demand and starting surge
The inverter must support the combination of loads that may operate together. This simultaneous demand can be very different from the daily energy total. A home may use a moderate amount of energy across the day but still create a high short-term demand when several appliances are switched on together.
Refrigerators, air conditioners, pumps and other motor-driven equipment can draw more power when starting than when running normally. The relevant starting requirement depends on the appliance and inverter, so it should be confirmed from product information rather than assumed from a universal multiplier.
4. Decide how much backup time you need
Battery storage depends on both the energy demand and the period you want the battery to support it. Decide whether you need short backup for essential loads, overnight support, or a broader daytime-and-night plan. Reducing optional loads during outages can substantially change the storage requirement.
Battery nameplate capacity is not the same as energy that should always be treated as usable. Battery chemistry, manufacturer operating limits, inverter settings, age, temperature and system losses matter. Use the applicable product documentation when converting a battery rating into an operating estimate.
5. Consider the solar array and the site
Solar panels must replenish the energy used while also working within the inverter and charge-controller limits. Panel output changes with sunlight, temperature, orientation, shading, dirt and system losses. A roof with morning or afternoon shade may perform differently from an unobstructed roof even when both use the same panel model.
A site review can check usable mounting space, roof or ground conditions, cable routes, equipment location, ventilation, distribution-board work and earthing requirements. These details can affect both the design and the written scope.
6. Leave room for real-world conditions and future loads
A design that only works when every assumption is perfect can be difficult to live with. Discuss realistic operating margins, seasonal conditions and any appliances you plan to add. Future air conditioners, pumps, freezers or office equipment should not be hidden from the sizing conversation.
At the same time, buying capacity without a clear load plan is not automatically better. A measured load list helps the system designer explain where capacity is needed and which usage changes could reduce the final requirement.
What to send when requesting a quotation
- Your appliance list, quantities and rating-plate watts where available.
- Expected hours of use and which loads must work overnight.
- The loads likely to start or run together.
- Your preferred essential and optional loads.
- Site location and any known roof, shading or access information.
- Photographs or a site-assessment appointment if requested.
Key takeaway
Start with an honest load audit, then confirm simultaneous demand, backup time, battery operating limits, solar conditions and the installation site. Leaf Solar’s calculator can help organise an early estimate, but the final system should be confirmed against actual appliance and site information.
This educational guide supports early planning. A final solar-system design and quotation should use confirmed appliance information, product specifications and relevant site details.