Reference
Solar energy glossary: every term on a Nigerian solar quote, explained
Every number PureWatts publishes carries a definition, a unit and the assumption behind it. This glossary is that definition layer, written for building owners and installers rather than analysts.
LCOE (levelised cost of energy)The average cost of every kilowatt-hour a solar system produces across its life, once the capital cost, replacements and maintenance are spread over the energy it delivers.Payback periodThe number of years of savings needed to recover the capital cost of the system.IRR (internal rate of return)The annual return the solar investment earns, expressed like a bank rate, over the system's life.NPV (net present value)The value of all future savings in today's money, minus what the system costs to build.Latent demandThe energy a building would use if power were always available — not the energy it actually consumes today.Merit orderA way of valuing solar where each kilowatt-hour displaces the most expensive energy first — generator fuel before grid supply.Energy independenceThe share of a building's energy that the solar and battery system supplies on its own.Usable roof areaThe part of a roof that can carry panels once orientation, shading, setbacks and obstacles are removed.Grid availabilityThe share of hours the grid is actually delivering power to a location, derived from night-time lights.Generator cost per kWhThe all-in cost of a self-generated kilowatt-hour, at the fuel the building actually burns — petrol for most homes, diesel for commercial sites.Capex (capital cost)The upfront cost of installing the system: panels, inverter, battery, mounting and labour.Solar sizing scenarios (sc1, sc2, sc3)Three ways of sizing the same roof: solar only, solar plus battery sized to full demand, and solar plus battery sized to what the building spends today.
How these numbers are produced
Approach A — energy value (upper bracket)
Sizes the system to the building's full latent demand and values that energy at the mixed grid/generator tariff. It answers what the energy is worth — not what anyone currently pays.
Approach B — cash saved (lower bracket)
Sizes the system to demand that is actually served today, values it by merit order (solar displaces generator kWh first) and caps it at current spend. It answers what a building stops paying.
Cohort: Viable rooftops (≥0.6 kWp potential).
- Demand is modelled latent demand, not metered consumption.
- Fuel is priced at ₦1,800/litre (operator-set). NBS reported ₦3,277/litre for May 2026 — on that basis every naira figure here is roughly 1.8× understated.
- Generator ownership is a model output, not a survey result: it follows from the grid-availability scale and the 25% demand-suppression assumption.
- Approach A prices energy nobody currently buys. Its savings must never be read as cash saved.
- Demand is MODELLED LATENT demand, not metered consumption.
- Generator ownership is model output, not survey.
- Medians do not combine across groups — re-derive from the histograms.
- Per-building files are float32 with 4 significant figures; cast to float64 before summing, because polars keeps Float32 sums in Float32.
- Null scenario fields mean the roof cannot host 0.6 kWp, not zero savings.
- `genset` was previously named `diesel` and now uses the segment's real fuel.
- Ordering holds by construction: grid savings < mixed < genset.