Off-Grid by Design: Techno-Economics of a Solar-Wind-Hydro Microgrid in Rural Nepal

Nepal generates most of its electricity from hydropower, yet still imports a large share and endures frequent outages. Extending the national grid across steep, sparsely populated terrain is slow and expensive, so for the settlements it has not reached, the practical path to reliable power is local generation from whatever the site offers - sun, wind, a nearby river - with storage to bridge the gaps. A 2023 techno-economic study[1] worked this out in detail for one Himalayan village, and this review unpacks its model, its data, and how the result compares with rural-electrification work worldwide.

The site, Thakle Namuna Basti, sits about 5 to 6 km from Bahunepati in Melamchi Municipality, Sindhupalchowk. It is a planned settlement of 32 near-identical houses and roughly 130 residents, rebuilt by Nepal's Department of Urban Development and Building Construction under the National Reconstruction Authority, with support from Oxfam Nepal, after the region's earthquakes. Most families belong to the Tamang community and depend on agriculture. Cooking runs on fuelwood, gathered largely by women at a real cost in time, while electricity mostly powers lighting.

Turning a village into a model

The analysis was built in HOMER Pro, an industry-standard optimiser for distributed energy systems. Because there are no utility bills to read, household demand was reconstructed from a field survey and cross-checked against appliance use and national load patterns, yielding a profile that averages 236.99 kWh per day and peaks near 41.5 kW.

Every candidate system was scored on four numbers that decide whether a rural energy project survives in practice:

• Net Present Cost (NPC) - the total lifetime cost of building and running the system.
• Levelized Cost of Electricity (LCOE) - the price per kWh that cost implies.
• Operating cost - the recurring annual burden after installation.
• Internal Rate of Return (IRR) - whether the investment pays back at all.

The resources on hand

Before any hardware is chosen, the model characterises the renewable resource - solar from the U.S. National Renewable Energy Laboratory, wind and temperature from NASA reanalysis, and river flow from ICIMOD. Two resources carry the system, and usefully they are anti-correlated: solar peaks in spring while wind is strongest in the dry pre-monsoon months.

A third resource, the nearby Sindhu River, adds micro-hydro following P = rho Q g H, with output rising sharply through the monsoon exactly when solar dips. No single source is dependable year-round, which is the whole case for a hybrid.

Building the system

The optimiser combines generation, storage and power conversion, sizing each element to meet demand without paying for idle capacity. Both a fully off-grid configuration and a grid-connected one, able to sell surplus back, were modelled.

Each element was specified to real, priced hardware rather than idealised placeholders:

What it costs, and what moves the number

Instead of a single answer, the study sweeps the grid power price and the sell-back rate to map how lifetime cost responds. In the grid-connected base case at a $0.14/kWh power price, the system lands at an NPC near $76,600 and an LCOE of $0.062/kWh; the cost-optimised architecture pulls NPC down to about $70,500 and LCOE to $0.059/kWh, and at higher sell-back rates the annual operating cost approaches, or even crosses, zero.

Two points stand out. The optimised architecture consistently undercuts the base case by roughly $6,000 to $11,000 in NPC - the value of letting the optimiser, not intuition, pick the mix. And the system is resilient to a rising grid price: as power climbs from $0.14 to $0.16/kWh, the optimised NPC barely moves, because the renewable core already carries most of the load.

An LCOE near $0.06/kWh puts locally-generated renewable power in the same range as many grid tariffs - for a village the grid may not reach for a decade.

How Thakle compares to the literature

A single case study is a data point; its value grows when read against comparable work. HOMER-based analyses of rural and island microgrids across South Asia, Southeast Asia and Africa provide a natural benchmark for whether Thakle's cost of energy is cheap, typical, or optimistic.

The verdict is favourable. Thakle's roughly $0.06/kWh sits at the low end of a benchmarked range spanning about $0.03 to $0.36/kWh. It is matched only by other hydro-rich, largely diesel-free designs - a Cameroon PV/micro-hydro/battery system[2] and a Bangladesh PV/wind/flow-battery system[3] - while diesel-inclusive or PV-only systems land far higher, from India[4] to island hybrids in the Philippines[5]. The common thread among the cheapest systems is exactly Thakle's: abundant micro-hydro displacing costly diesel and sparing the budget from battery over-sizing.

These figures are directional rather than strictly like-for-like - studies differ in discount rate, project lifetime, load size and base year - but the pattern is consistent and places the Thakle design among the more cost-effective rural microgrids in the literature.

Limitations worth naming

• Demand is estimated, not metered - survey-based load carries uncertainty, and demand tends to grow once reliable power arrives.
• The battery modelled is lead-acid: cheaper up front but shorter-lived than lithium, which could shift lifetime economics.
• The lowest-cost architecture on paper is not automatically the one a community will operate and maintain - ownership, servicing and trust decide that.

Why it matters

The lasting result is the method. A modest hybrid of the resources a site already has - sun, wind, a river, and storage to bridge them - can deliver dependable electricity at a cost that withstands scrutiny. Multiplied across the thousands of settlements where grid extension lags population growth, the same modelling recipe becomes a planning tool for rural electrification at scale.

@article{shah2023technoeconomic,
  author  = {Shah, Malesh and Koirala, Kshitiz and Upreti, Saugat and Sanjel, Nawaraj},
  title   = {Techno-Economic Analysis of Energy Systems in Thakle Namuna Basti: A Case Study},
  journal = {IOP Conference Series: Materials Science and Engineering},
  volume  = {1279}, number = {1}, pages = {012007}, year = {2023},
  doi     = {10.1088/1757-899X/1279/1/012007}
}