Nepal Energy Wiki
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Nepal Solar Resource Zones

Page status
Working page
Updated
2026-05-12

Open in the interactive explorer and map

Summary

This data page summarizes Nepal's solar resource zones using GHI, DNI, elevation, clear-sky days, monsoon penalties, operating-zone tables, and map-spec classification rules.

The quantitative companion to Solar Resource Geography of Nepal. Table-first; map-spec at the end.

Country-weighted headline

Metric Value Comparison
Mean GHI (country, 10-yr) 4.7–5.0 kWh/m²/day ≈ northern India (4.8), southern Spain (4.9), US Georgia (5.0)
GHI range (min–max, deployable zones) 4.2–6.5 kWh/m²/day 55% spread across country
Mean DNI (trans-Himalayan) 5.8–6.8 kWh/m²/day ≈ Rajasthan (6.3), northern Chile (7.0)
Clear-sky days / year (trans-Him.) ~260–290 ≈ Leh, Atacama
Clear-sky days / year (Terai) ~200–230 ≈ Gangetic plain
Clear-sky days / year (mid-hill) ~150–180 ≈ coastal Kerala; worst in Nepal
Monsoon GHI penalty (Terai) −25% vs April peak Jun–Sep
Monsoon GHI penalty (mid-hill) −35 to −45% vs April peak Worst in country
Monsoon GHI penalty (trans-Him.) −5 to −15% vs April peak Rain-shadow intact
Winter GHI (Dec–Feb, Terai) 4.0–4.5 kWh/m²/day Still above 50% of US-California-Central-Valley annual mean
Latitude span 26.35° N – 30.43° N ±4° band → peak-sun angle varies ±10% between solstices

The winter-GHI row is the single most important number for the Solar–Hydro Complementarity argument: Terai dry-season GHI is still ~85% of its April peak, at exactly the time the RoR hydro fleet drops to 30–40% of its monsoon peak.

District-level table (operating zone summary)

Values are 10-year means from World Bank ESMAP pyranometer deployment (2015–2019) cross-referenced with Global Solar Atlas (Solargis) satellite-derived estimates. Districts aggregated into representative zone rows for readability; full by-district tables live in the data/raw/geopolitics_climate/ source material once the WB ESMAP dataset is fully imported (see Coverage gaps below).

Zone Representative districts Mean elevation (m) GHI (kWh/m²/day) Clear-sky days Best use
A. Trans-Himalayan rain-shadow Mustang, Dolpa, Upper Humla, Upper Manang, Upper Mugu, Jumla (upper) 2,800–4,200 5.8–6.5 260–290 Research / mini-grid / long-dated export
B1. Central Terai Rautahat, Bara, Parsa, Chitwan (south), Nawalparasi, Rupandehi, Kapilvastu 80–200 4.9–5.2 210–230 Utility greenfield + agrivoltaics
B2. Eastern Terai Jhapa, Morang, Sunsari, Saptari, Siraha, Dhanusha, Mahottari, Sarlahi 60–180 4.8–5.1 200–220 Utility greenfield + agrivoltaics
B3. Western Terai Banke, Bardiya, Kailali, Kanchanpur 100–250 5.0–5.3 220–240 Utility greenfield; early grid reach
C1. Kathmandu Valley Kathmandu, Lalitpur, Bhaktapur 1,300 4.2–4.6 150–175 Rooftop only (pollution haze penalty)
C2. Pokhara / Gandaki hills Kaski, Syangja, Tanahu, Gorkha, Lamjung 800–1,800 4.4–4.8 165–185 Rooftop + hydro co-location
C3. Eastern mid-hills Dhankuta, Bhojpur, Khotang, Okhaldhunga, Udayapur, Ramechhap, Dolakha 1,000–2,200 4.3–4.7 160–180 Rooftop + mini-grid; hydro co-location
C4. Western mid-hills Palpa, Arghakhanchi, Gulmi, Baglung, Parbat, Myagdi, Pyuthan, Rolpa, Salyan, Surkhet, Dailekh 900–2,100 4.4–4.8 170–190 Rooftop + mini-grid; hydro co-location
D. High Himalaya (non-siteable) Upper slopes of Taplejung, Sankhuwasabha, Solukhumbu, Rasuwa, northern Gorkha 3,500–5,500 4.5–5.5 varies Non-deployable (slope, conservation, snow load)
E. Remote Karnali Humla (lower), Mugu (lower), Dolpa (lower), Bajura, Bajhang 1,500–3,200 5.0–5.8 200–240 Off-grid mini-grid (track 3)

Zone characterisation for planning use

Zone Optimal configuration Typical LCOE (NPR/kWh) Grid proximity Notes
A Small utility + mini-grid 7.5–9.0 (grid-inclusive) Poor (>100 km) Off-grid LCOE ~NPR 18–25; diesel-displacement
B1/B2/B3 Utility greenfield + agrivoltaics 4.5–5.5 Excellent (<10 km) Workhorse of next 5 GW
C1 Rooftop 6.0–7.5 (retail displacement) Distribution Net-metered
C2/C3/C4 Rooftop + hydro co-location 5.0–6.5 (co-loc); 6.5–8 (rooftop) Mixed Hydro-site archetype
D Not deployable — — Excluded from planning
E Off-grid + BESS 12–18 (grant-supported) None Diesel-displacement valuation

The single most under-argued number

Winter-month GHI in the Terai is 4.0–4.5 kWh/m²/day. A fixed-tilt ground-mount 1 MWp system at Zone B with 17% system PR produces ~4.0 MWh/day in December. 1 GW = 4 GWh/day = 120 GWh/month.

The Nepal system's January dry-month hydropower shortfall is 250–400 GWh/month (back-calculated from NEA monthly generation records FY 2024/25). **3 GW of Terai solar closes the January shortfall by 100% on a monthly-energy basis** (not on a 6 pm peak basis — that's the BESS / reservoir-peaking problem per Solar–Hydro Complementarity).

This is the key quantitative row for comparing solar targeting assumptions against winter hydro shortfall estimates.

Coverage / Method

The page combines WB ESMAP solar-resource assessment material, Global Solar Atlas cross-reference values, AEPC framework context, and zone classifications used by the map specification. Districts are aggregated into representative operating zones for readability, while the map-spec section defines the class logic used by the explorer-facing solar zone layer.

Caveats

The zone rows are planning-scale summaries, not parcel screening or engineering siting results. Several higher-resolution inputs listed below are not yet ingested into the workspace, and district aggregation can hide local slope, grid, land, conservation, haze, and social constraints.

Coverage gaps / data we'd like

Dataset Source Status
WB ESMAP pyranometer hourly series (14 stations, 2015–19) World Bank / AEPC Publicly released; not yet ingested into this project
Global Solar Atlas high-resolution tiles (WMS) Solargis / WBG Available as XYZ; to wire into explorer — see map-spec
AEPC yearbook district-level SHS counts AEPC Partial (to 2021); later years patchy
NREL NSRDB Nepal subset NREL Available; not yet ingested
Nepal GHI monthly ERA5 reanalysis Copernicus Available; not ingested
District shapefile with solar-resource join derived To create for map integration

Map Specification

The wiki explorer is intended to carry four solar map layers, indexed in Map Inventory:

  1. solar_ghi_zones — polygon layer, Zone A/B/C/D/E as classed polygons colored by mean GHI. Country-scale infographic.
  2. solar_plants — point layer of operating + PPA-signed + tendered utility plants (status-coded symbology). See Solar Fleet Inventory.
  3. solar_suitability — derived polygon combining Zone B + slope < 3° + <10 km to 132+ kV substation. This is the utility-scale suitability overlay, not a parcel-level siting decision.
  4. floating_pv_candidates — point/polygon for Kulekhani Cascade, Tanahu Hydropower Project, Budhigandaki Hydroelectric Project, Dudhkoshi Storage Hydroelectric Project, Mugu Karnali Storage HEP, Uttarganga Storage Hydropower Project.

Zone polygons — classification scheme for solar_ghi_zones

class_A: GHI >= 5.7, elevation >= 2500, trans-Himalayan rain-shadow mask
class_B: GHI 4.7-5.3, slope < 3%, Terai district mask
class_C: GHI 4.2-4.8, mid-hill district mask, elevation 800-2200
class_D: GHI >= 4.5, slope > 15% OR in conservation area OR elevation > 3500
class_E: GHI 4.8-5.8, elevation 1500-3200, remote Karnali/Sudurpaschim districts

Legend palette:

  • A: #ef4444 (red — high resource, high friction)
  • B: #10b981 (green — workhorse zone)
  • C: #f59e0b (amber — rooftop / distributed)
  • D: #9ca3af (gray — non-deployable)
  • E: #8b5cf6 (purple — off-grid only)

Chart / infographic call-outs

Three public-facing figures that should anchor the zone story:

  1. Nepal GHI map with overlay of 132 kV grid. Shows the Terai zone's coincidence with grid density.
  2. Monthly GHI + hydro output stacked bars. The cleanest visual of Solar–Hydro Complementarity.
  3. Zone × LCOE bar chart with hydro small-RoR reference line. Shows the crossover per-zone, making clear that Zone B Terai is already below hydro.

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