Solar Power for Multi-Tenant Apartment Buildings in Nigeria: Shared Systems, Flat-Level Metering and Fair Cost Allocation
A solar installation for a block of flats is not simply a larger version of a single-family home system. A building with several tenants has different usage patterns, shared services, billing questions and expectations about who gets power when the battery is low.
For landlords, property developers and facility managers, the central question is not only how many panels or batteries to install. It is how to design a system that serves the intended loads, measures each unit’s consumption fairly, protects the existing electricity supply and makes operating costs understandable.
This guide explains the decisions to make before installing solar in a multi-tenant building in Nigeria. The numerical example is illustrative only—not a quotation, a promise of performance or a record of a Zookie Solar installation.
1. Decide what the solar system is meant to power
Begin by agreeing on the service level. A shared system can be designed in several ways, and each option creates different expectations.
- Common areas only: corridor and security lighting, gate controls, shared internet equipment, CCTV and selected water-pumping loads.
- Essential circuits in each flat: agreed lighting points, fans, television, router, phone charging and perhaps a carefully assessed refrigerator circuit.
- Broader apartment supply: more appliances and potentially air conditioners, irons, kettles or cooking equipment. This requires a much more demanding load and peak-power assessment.
Do not promise that every flat can run every appliance simultaneously unless the design has been calculated for that operating condition. A system that keeps lights and fans on may not be designed to support multiple air conditioners, pressing irons and water pumps at the same time.
Write down what is included, what is excluded and what happens during low battery conditions. This avoids a mismatch between the system that was purchased and the system tenants expect to use.
2. Audit each flat and the building’s shared loads
A site survey should map every flat separately, then add the building’s common services. Record appliance ratings, realistic operating hours, motor starting requirements, daytime versus night-time use, and the loads that must remain available during an outage.
Separate loads into practical tiers
- Tier 1 — essential: selected lights, fans, communications equipment and other agreed priority loads.
- Tier 2 — managed: refrigerators, televisions, computers and other loads that can be supported subject to the system’s capacity and usage rules.
- Tier 3 — high-demand or discretionary: air conditioners, electric heaters, kettles, pressing irons, large pumps and similar appliances. These may need dedicated circuits, time scheduling or exclusion from the shared backup system.
The labels are planning tools, not universal rules. A refrigerator may be essential for one tenant and a discretionary load for another. The owner and occupants should agree on priorities before equipment is selected.
3. Worked example: an eight-flat building
The following hypothetical example shows how an energy audit can translate into an initial design discussion. Actual consumption can differ substantially with appliance efficiency, weather, occupancy, user behaviour and the number of hours each appliance operates.
Illustrative daily energy per flat
- LED lighting: 100 W combined × 5 hours = 0.50 kWh/day.
- Two fans: 120 W combined × 8 hours = 0.96 kWh/day.
- Television, router and device charging: 150 W combined × 4 hours = 0.60 kWh/day.
- Refrigerator: assumed 0.80 kWh/day, based on an illustrative equivalent running-energy estimate; the real figure should be measured or estimated from the actual appliance.
Estimated total: 0.50 + 0.96 + 0.60 + 0.80 = 2.86 kWh per flat per day. Rounded for planning, that is about 2.9 kWh/day. For eight flats, the illustrative total is about 22.9 kWh/day.
Add common-area energy
- Security lighting: 150 W × 10 hours = 1.50 kWh/day.
- Gate and access-control equipment: assumed 0.40 kWh/day.
- Water pumping: assumed 1.10 kWh/day; confirm the pump’s actual input power, run time and starting current.
- Shared communications/security equipment: assumed 0.60 kWh/day.
The common-area estimate is 3.60 kWh/day. Adding it to the eight flats gives approximately 26.5 kWh/day. This is a model for planning—not a prediction that the building will use exactly this amount.
4. Turn energy demand into a preliminary solar and battery estimate
For an early illustration, assume 4.5 equivalent peak-sun-hours per day and an overall planning factor of 0.75 to account broadly for system losses. These are assumptions for this worked example, not a guaranteed local yield.
A simplified PV estimate is: 26.5 kWh/day ÷ (4.5 hours × 0.75) ≈ 7.85 kWp. Adding a provisional 20% planning allowance gives about 9.4 kWp of PV capacity. A qualified designer must check the site’s solar resource, roof area, orientation, shading, module/inverter compatibility, seasonal conditions and actual demand before specifying the array.
Battery capacity must be based on the energy required during the hours when solar production is insufficient—not just on the building’s daily total. If, for illustration, 65% of the 26.5 kWh daily demand must be supplied after useful solar production, the AC energy requirement is about 17.2 kWh. Assuming 85% usable battery depth of discharge and 90% conversion efficiency, the simplified nominal battery estimate is 17.2 ÷ (0.85 × 0.90) ≈ 22.5 kWh, before any additional resilience allowance.
That result is only a starting point. The final battery design should consider the required autonomy, battery chemistry and manufacturer limits, temperature, ageing, reserve settings, expected grid availability and whether all flats or only essential circuits must remain powered. Longer autonomy requires more stored energy.
Do not select the inverter from the daily kWh figure alone. Its continuous power rating, surge capability, phase arrangement and load-management strategy must suit the likely simultaneous demand and the starting characteristics of motors such as pumps. A system designed for lights and fans may be unsuitable for unrestricted air-conditioning use.
5. Choose an architecture that can be measured and maintained
Option A: solar for common services
A dedicated system for corridors, security equipment, gate controls and agreed shared services is often the simplest first phase. It avoids making every flat dependent on a single central inverter and can be expanded after actual common-area demand is understood.
Option B: a central system with separately measured flat circuits
A central inverter and battery plant can serve agreed circuits in multiple flats, but the distribution design needs careful engineering. Each flat’s solar-backed supply should be clearly defined, protected and metered downstream. Shared services should have their own circuit and, where appropriate, their own meter. Existing grid supplies must be integrated safely, with suitable isolation, protection and changeover arrangements.
A sub-meter measures energy passing through the circuit where it is installed; it does not automatically identify whether each unit of energy came from PV, the battery or the grid. If source-specific accounting matters, the monitoring and metering design must support it.
Option C: an independent system for each flat
Individual systems can give each household more control over its own usage and backup priorities. However, they may duplicate inverters, batteries and maintenance work, and the building must still address shared loads such as security lighting, gates and water pumps. Compare lifecycle cost and maintenance responsibility—not only the initial purchase price.
6. Make the metering and cost-allocation rules transparent
A shared solar system can become a source of conflict if tenants do not know what is measured, what they are paying for or how low-battery periods are handled. Before commissioning, document the following:
- Which circuits each flat receives from the solar system and which remain on its existing supply.
- Whether each flat has a dedicated sub-meter for the solar-backed circuit, plus a separate measurement point for common-area loads.
- How readings are recorded, when billing periods begin and end, and how tenants can review their readings.
- How common-area energy, conversion losses, maintenance and battery replacement are allocated.
- Who can access monitoring data, who handles faults and what happens when a meter or communication link fails.
- Which loads may be limited during low battery conditions and how occupants will be notified.
Avoid dividing the total energy bill equally when actual unit consumption differs, unless everyone has knowingly agreed to a clearly explained arrangement. A transparent record of meter readings, common-area consumption and agreed charges is more defensible than estimates made after a dispute starts.
Also distinguish between measuring usage and charging for electricity. If the proposed arrangement involves supplying multiple customers, charging tenants for electricity or operating a distribution network, do not assume that installing sub-meters alone settles the regulatory question. Obtain project-specific advice on the applicable federal or state electricity rules before finalising the commercial model.
7. Safety and regulatory checks are part of the design
A shared system should be designed and installed by competent electrical professionals. The design should address earthing and bonding, overcurrent protection, battery isolation, cable protection, surge protection where required, clear circuit labelling, ventilation and access for maintenance. The system must not energise the public grid through an unsafe connection. Any grid-parallel operation or export needs the applicable technical approvals and compliant equipment.
Nigeria’s electricity market has been decentralised under the Electricity Act 2023, and regulatory responsibility can depend on the activity and state. NERC published the Mini-Grid Regulations 2026 on 10 April 2026 and provides guidance on mini-grid permits and registration. These rules are not a blanket statement that every private apartment solar installation is a mini-grid; they are a reason to check the project’s actual structure and jurisdiction rather than rely on assumptions.
Keep a commissioning pack containing the as-built single-line diagram, equipment schedules, protection settings, meter identifiers, test results, user instructions and warranty documents. Give the facility manager a written operating procedure and a contact for technical support.
8. Commission the system with tenants’ real expectations in mind
Before handover, test each flat’s designated circuits, the common services, the transfer between available sources, the metering readings and the behaviour of the system under realistic load. Verify that the inverter’s monitoring data agrees reasonably with the installed meters. Demonstrate what happens when battery reserves are reached and which loads are prioritised.
A short operating guide should explain how to read the meters, report a fault, avoid overloading the backed-up circuits and understand planned maintenance. If tenants change appliances or the property adds new flats, recheck the demand before connecting them to the system.
Conclusion: design the building, not just the equipment list
The strongest multi-tenant solar proposal begins with a clear service agreement, a measured load profile and an architecture that makes each flat’s supply understandable. Solar panels, inverters and batteries matter—but so do circuit boundaries, individual readings, common-area accounting, safety and long-term maintenance.
Zookie Solar Ltd can help property owners and facility managers assess the building’s loads, compare shared and individual system options, and plan a system around the intended service level. Request a site-specific consultation before committing to equipment or promising tenants a particular level of backup.
Zookie Solar Ltd — Built on Power. Driven by Excellence.
Email: admin@zookiesolar.com
