Introduction
This is a twenty-post engineering series on off-grid solar system design, installation, commissioning, and economics. Every post is built around a single worked system a 4,916Wh residential installation in coastal West Africa and every calculation in every post uses real numbers from that system. The methodology applies to any tropical off-grid installation. The numbers are Port Harcourt-specific and can be replaced with any site’s values.
The series is not designed to be read from beginning to end in a single session. It is designed to answer the specific question you have right now and route you to the adjacent posts that provide the context you need. This index tells you where to start based on your situation, lists every post in the series in order with a one-line description of what it covers, and describes the worked system that connects every post to every other one.
Find your situation in Section 1. Start with the link that matches your question. Follow the internal links from there.
Start Here Based on Your Situation
“I am considering solar does it actually make financial sense in Port Harcourt?”
The answer requires understanding what you are currently spending on your generator, not what your electricity bill says. Start with off-grid solar vs generator in Nigeria: why generator power costs over ₦5 million per year. It calculates the true annual cost of generator operation including fuel, maintenance, and replacement amortisation, computes the payback period against that baseline, and provides a 15-year total cost of ownership comparison. Most readers find the result significantly more favourable than they expected before reading it.
“I don’t know which type of solar system I need off-grid, hybrid, or grid-tied”
The answer depends on how many hours of grid supply your site actually receives, measured over 30 days not estimated. Start with off-grid vs hybrid vs grid-tied solar: which solar architecture is right for your site?. It provides a four-input site assessment framework that produces a deterministic architecture recommendation, a financial comparison between all three architectures for the same daily demand, and three worked scenarios covering the range of Port Harcourt grid conditions.
“I want to design a complete off-grid system from scratch”
Start at the beginning of the methodology and follow the series in order. The correct starting point is how to do a proper load audit before sizing an off-grid system, which establishes the daily energy demand figure that every downstream calculation depends on. The overview of the complete design process is at designing an off-grid power system using lithium batteries.
“My system keeps tripping, shutting down, or not charging correctly”
Start with top 10 costly off-grid solar mistakes and how to avoid them, which maps ten recurring failure patterns to their root causes, diagnostic tests, and corrective actions. If the fault requires deeper diagnosis, go to off-grid solar system commissioning and troubleshooting: the complete field guide, which provides a structured four-step diagnostic framework and detailed pathways for the four most common fault conditions.
“I want to add more panels, batteries, or a new load to my existing system”
Start with off-grid solar system expansion without triggering failures: the complete constraint analysis. It identifies the five constraints every expansion must be checked against before any component is purchased, works through the constraint analysis for a complete expansion scenario, and shows which components require upgrade. The commissioning documentation from your original installation is the primary reference if you do not have it, the expansion guide explains how to proceed without it.
“I am an installer and I want to learn the correct methodology”
Start with designing an off-grid power system using lithium batteries for an overview of the complete design process, then work through the series in full from the load audit through to the economics posts. The commissioning checklist at the complete off-grid system design checklist is the field document that consolidates every verification step into a single printable reference.
“I need to commission and document a system correctly”
Go directly to the complete off-grid system design checklist, which provides ten sequential stages with numbered pass criteria, verification methods, and sign-off rows for field recording. The commissioning sequence and documentation requirements are in off-grid solar system commissioning and troubleshooting: the complete field guide.
The Complete Series All Posts in Order
Group 1: Load Analysis and Design Foundation
- How to do a proper load audit before sizing an off-grid system How to identify every load, measure running power rather than use nameplate wattage, and calculate the daily energy demand figure that every downstream sizing calculation uses.
- Peak load vs average load: why the difference can ruin your off-grid design Why the inverter must be sized for the peak simultaneous load including motor starting surge, not the average load or the sum of nameplate ratings.
- How to account for phantom loads and standby power in off-grid energy budgets How to measure and quantify the overnight phantom load that reduces effective battery autonomy by 15 to 25 percent on most residential installations.
Group 2: Solar Array
- Solar array sizing for off-grid lithium battery systems How to calculate minimum array power from daily energy demand, peak sun hours, and a four-factor derating calculation, with a design margin for seasonal variation.
- Series vs parallel vs series-parallel solar array wiring How series and parallel configurations affect string voltage, current, and MPPT compatibility, with the cold Voc and hot Vmp checks that determine whether a string configuration is safe for the selected controller.
Group 3: Charge Controllers
- MPPT charge controller: how they work and how to select one How MPPT tracking works, how to size the controller’s output current for the battery bank, how thermal derating affects derated output, and how BMS communication changes the charge profile.
- How to size and select an MPPT charge controller for a 48V LiFePO4 off-grid system The complete verification sequence for the Victron SmartSolar MPPT 150/60 on the cluster system, showing every check from cold Voc to thermal derating to BMS communication compatibility.
Group 4: Inverters
- How to select an off-grid inverter: continuous rating, surge, voltage architecture, and BMS communication The three-number inverter problem, peak simultaneous load and surge calculation, 48V architecture argument, standby power, LiFePO4 voltage settings, and BMS communication architecture.
- Off-grid inverter sizing: 3kVA vs 5kVA Victron Multiplus-II complete worked example The complete verification sequence for the Multiplus-II 48/3000 on the cluster system, including the surge failure and soft starter resolution, LVC and HVC settings, and AC input current limit calculation.
Group 5: Wiring and Installation
- DC cable sizing for off-grid solar systems: the two-constraint framework How to apply thermal derating and voltage drop calculations simultaneously to every DC cable run, how to rate fuses to protect the cable rather than the load, and the single earth bond point rule.
- AC wiring for off-grid solar systems: cable sizing, earthing, protection, and distribution RCBO specification for every circuit, the neutral-earth link switching requirement, Type 2 SPD at the distribution board incomer, and earth electrode impedance measurement.
Group 6: Energy Storage and Commissioning
- Battery bank sizing for off-grid systems: capacity, BMS selection, and cycle life The three-variable sizing framework, the DoD-longevity trade-off, BMS communication architecture, and the temperature installation requirements for tropical off-grid deployments.
- Off-grid solar system commissioning and troubleshooting: the complete field guide The seven-stage commissioning sequence, how to read Cerbo GX and VRM data, the four most common fault conditions with diagnostic pathways, DC ground fault measurement, and battery state of health monitoring.
- Off-grid solar system expansion without triggering failures: the complete constraint analysis The five-constraint expansion framework, three array expansion scenarios, inverter upgrade paths, battery bank expansion limits, load expansion calculation, and generator review for expanded systems.
Group 7: Economics, Comparisons, and Reference
- Off-grid solar vs generator in Nigeria: why generator power costs over ₦5 million per year The full generator running cost calculation including fuel, maintenance, and replacement amortisation; payback period at current Port Harcourt fuel prices; 15-year TCO comparison; NPV analysis; and the financing cash-flow argument.
- How to size an off-grid solar system for commercial buildings The three commercial load categories, motor load surge current identification, overnight standby load battery sizing, three-phase inverter architecture, and the complete specification for a ten-staff office building.
- Generator sizing for off-grid solar systems: integration and hybrid operation guide The three-demand generator sizing calculation, AC input current limit configuration, power quality verification under combined load, auto-start configuration, PowerAssist mode, and run time optimisation.
- Top 10 costly off-grid solar mistakes and how to avoid them Ten recurring mistakes organised by design, installation, commissioning, and post-commissioning stage, each with a root cause, symptom, diagnostic test, and corrective action, plus a master troubleshooting reference table.
- The complete off-grid system design checklist Ten sequential stages from load audit to documentation handover, each with numbered pass criteria, a verification method, and a sign-off row for field recording. Designed to be printed and carried to site.
- Off-grid vs hybrid vs grid-tied solar: which solar architecture is right for your site? The four-input site assessment framework, financial comparison between all three architectures for Port Harcourt conditions, three worked scenarios, and the five most common architecture selection mistakes.
The Worked System
Every post in this series uses the same worked system as its numerical context. The worked system is a residential off-grid installation sized for a daily energy demand of 4,916Wh in coastal West Africa at approximately 6 degrees north latitude. Its components are six 400W panels wired in a 3S2P configuration producing a 2,400W array, a Victron SmartSolar MPPT 150/60, a Victron Multiplus-II 48/3000/35-32, four Pylontech US3000C battery modules producing a 14.2kWh bank at 48V nominal, a Victron Cerbo GX as the communication hub, and a 5kVA petrol generator with auto-start at 30 percent state of charge.
The worked system is not a product recommendation. It is a pedagogical tool. Every abstract methodology in the series has a concrete numerical instance in this system the cold Voc calculation produces 125.5V, the MPPT output current produces 35.9A, the battery-to-inverter cable is 35mm², the daily DoD is 38.5 percent. A reader who is uncertain whether a calculation is correct can verify it against the worked system values. A reader designing a different system replaces the inputs different panel wattage, different battery capacity, different daily demand and the methodology produces the correct output for their system.
Conclusion
Every calculation in this series connects to at least two others. The load audit produces the daily energy demand that feeds the array sizing. The array sizing produces the string configuration that feeds the MPPT Voc and current checks. The MPPT output current feeds the battery-to-inverter cable sizing. The cable sizing feeds the fuse ratings. The battery bank sizing feeds the BMS communication check. Follow any internal link in any post and you will be routed to the adjacent methodology without needing to return to this index.
The series is complete. The methodology covers every stage of an off-grid solar project from the first measurement to the final handover document, and every stage is connected to every other stage by a chain of calculations that can be verified, checked, and corrected at any point.
Start wherever your question is. Everything you need to answer it is here.
The full series begins at designing an off-grid power system using lithium batteries.
I am Engr. Ubokobong Ekpenyong, a solar specialist and lithium battery systems engineer with over five years of hands-on experience designing, assembling, and commissioning off-grid solar and energy storage systems. My work focuses on lithium battery pack architecture, BMS configuration, and system reliability in off-grid and high-demand environments.