Solar glossary
Merit order: what it means and why it matters
A way of valuing solar where each kilowatt-hour displaces the most expensive energy first — generator fuel before grid supply.
Why it matters in Nigeria
It is the only coherent basis on Bands B–E, where grid energy is rationed rather than freely purchasable. It is the conservative, cash-honest number.
How PureWatts measures it
Total Year 1 savings (Merit-order sized, merit order)
sum_sc3_y1_sav_meritorder_ngn
Sum over the buildings in the group. Year-1 savings against the baseline. Baseline: meritorder.
Solar + battery, merit-order sized: Same engine as sc2, but the target is what the building CONSUMES today x 1.5 (MO_SIZING_UPLIFT) rather than full latent demand.
In Osun, sizing sc2 to latent demand while crediting it only with displacing current spend produced a 6x-oversized system and a negative IRR that said nothing about solar. sc3 is the fix, not an alternative opinion.
Counterfactual: solar displaces the most expensive kWh first — generator before grid. savings = min(solar, genset_kWh) x genset_cost + max(0, solar - genset_kWh) x tariff. Approach B; the only baseline that is coherent for Bands B-E, where grid energy is rationed rather than purchasable.
Sum over the buildings in the group.
Total Life savings (Merit-order sized, merit order)
sum_sc3_life_sav_meritorder_ngn
Sum over the buildings in the group. 20-year savings against the baseline. Baseline: meritorder.
Solar + battery, merit-order sized: Same engine as sc2, but the target is what the building CONSUMES today x 1.5 (MO_SIZING_UPLIFT) rather than full latent demand.
In Osun, sizing sc2 to latent demand while crediting it only with displacing current spend produced a 6x-oversized system and a negative IRR that said nothing about solar. sc3 is the fix, not an alternative opinion.
Counterfactual: solar displaces the most expensive kWh first — generator before grid. savings = min(solar, genset_kWh) x genset_cost + max(0, solar - genset_kWh) x tariff. Approach B; the only baseline that is coherent for Bands B-E, where grid energy is rationed rather than purchasable.
Sum over the buildings in the group.
See these numbers for your area
Every state and local government area page reports merit order for its own rooftops. Browse the Nigeria rooftop solar data.