Solar Inverter for Water Pump, KUSUM Picks

ALMM and inverter compliance: MNRE’s current ALMM page publishes solar PV module and cell lists, not an inverter list. Verify the inverter’s exact model documents and applicable scheme or DISCOM requirements separately.

Water pump irrigation accounts for a significant share of India’s agricultural electricity consumption. Millions of farmers run diesel or electric pumps to water their fields, and both are expensive. Diesel costs ₹95–₹110 per litre in most states, while agricultural electricity tariffs, though subsidised, are rising. Solar changes the economics fundamentally: once panels are paid off, water costs nearly nothing per litre pumped.

The challenge is that pumps are not simple resistive loads. A water pump motor (whether a submersible borewell pump or a surface centrifugal pump) draws a sharp current spike every time it starts. Get the solar system wrong, and the inverter trips every morning when the pump tries to start. Get it right, and a well-designed solar pump system runs for 25 years with near-zero maintenance.

This guide explains the difference between a solar pump controller and a grid-tied inverter, the KUSUM components at a high level, and the inputs needed for pump sizing. It does not approve a Qbits model or establish scheme eligibility for a project.

Direct answer. A solar inverter for a water pump must be sized for inrush current, motors draw 5–7× their rated current at start-up. Use the Pump Sizing Triangle: (1) convert HP to kW (×0.746), (2) divide by motor efficiency (÷0.80), (3) multiply by 1.5 for inrush headroom. For standalone off-grid pumps, choose a dedicated solar pump controller with VFD; for grid-connected pumps under KUSUM Component-C, a standard on-grid inverter sized to the solar array is correct. KUSUM Component-B supports standalone solar pumps with central financial assistance of 30% of the benchmark cost (50% in special category states, per the MNRE PM-KUSUM page, read 14 October 2026), with any state share set by the state.

The sections below explain both topologies, walk through the sizing maths, and show where the KUSUM scheme fits into each.

Solar Pump Controller vs Solar Inverter: The Core Distinction

Many farmers and installers search for a “solar inverter for water pump” expecting to find a single product. The market actually offers two fundamentally different approaches, and choosing the wrong one wastes money or causes daily operational problems.

Standalone Solar Pump Controller (VFD-Based)

A solar pump controller (also called a solar pump drive or solar VFD) takes DC power directly from the solar panels and converts it to variable-frequency AC to drive the pump motor. The key feature is Variable Frequency Drive (VFD) control: the drive starts the motor at very low frequency (15–25 Hz) and ramps up to 50 Hz over 5–10 seconds. This eliminates inrush current almost entirely.

These systems are entirely off-grid. There is no grid connection. The pump only runs when the sun shines. Most controllers include dry-run protection (cuts off if the water level drops), solar input MPPT for maximum energy extraction, and a float switch input.

KUSUM Component-B systems use this topology. The system is self-contained: solar panels → pump controller → AC motor pump. No DISCOM approval is required.

Grid-Connected On-Grid Inverter (KUSUM Component-C)

In a grid-connected pump setup, the pump motor continues to draw power from the DISCOM feeder as it always has. The solar system (panels and an on-grid inverter) is installed on the farm to generate power that offsets the electricity consumed by the pump. Net metering (or gross metering, depending on state policy) allows the DISCOM to credit or purchase the exported solar units.

The on-grid inverter does not drive the pump motor directly. It simply exports solar power to the grid or premises bus. The pump’s motor starter, direct-on-line contactor, or existing soft-starter remains unchanged. This is a straightforward grid-tied rooftop or ground-mount solar system installed near the agricultural feeder, exactly what Qbits on-grid inverters are designed for.

HP to kW Conversion and Inrush Current: The Maths Behind Pump Sizing

Every pump sizing conversation starts with horsepower. Motor nameplates in India show HP. Solar inverters and controllers are rated in kW. The conversion and the inrush factor together determine the minimum inverter or controller rating.

The Pump Sizing Triangle

This is the named framework for this guide. Three steps, applied in sequence, give the minimum inverter or controller rating for any pump motor.

1. Convert HP to kW: Multiply HP by 0.746. A 1 HP motor is 0.746 kW shaft power; a 2 HP motor is 1.49 kW; a 5 HP motor is 3.73 kW.
2. Account for motor efficiency: Divide by motor efficiency (typically 0.78–0.82 for standard squirrel-cage induction motors). A 1 HP motor with 80% efficiency draws 0.746 ÷ 0.80 = 0.93 kW from the supply. This is the electrical input power, what the inverter or controller must deliver during normal running.
3. Add inrush headroom: Multiply electrical input power by 1.5 to 2.0 to get the minimum inverter rating. A 1 HP motor drawing 0.93 kW at full load will surge to 4.65–6.51 kW during the start-up spike. A solar pump controller with VFD eliminates most of this surge, so the headroom factor drops to 1.25–1.5. An on-grid inverter powering a direct-on-line motor starter needs the full 1.5–2.0× headroom.

Apply the Pump Sizing Triangle to any HP rating before ordering equipment:

30 lakh. The number of diesel-powered agricultural pumps MNRE has targeted for solarisation under PM-KUSUM by 2026 across all three components. Replacing diesel pumps with solar eliminates an estimated 3 to 5 tonnes of CO₂ per pump per year and saves farmers ₹40,000–₹80,000 annually in fuel costs. Source - MNRE PM-KUSUM Programme, 2026.

Pump irrigation is a large agricultural electricity load that many state DISCOMs subsidise, so shifting it to solar is both an environmental and a fiscal priority, which is part of the reason the KUSUM programme exists.

KUSUM Scheme: Which Component Applies to Your Pump

The KUSUM scheme (Kisan Urja Suraksha evam Utthaan Mahabhiyan) has three components. Farmers often enquire about subsidies without knowing which component fits their situation. The table below maps common scenarios to the correct sub-scheme.

Component-A: Solar Power Plants on Farm Land

Component-A targets land-owning farmers with barren or fallow land. A developer or the farmer installs a ground-mount solar power plant (up to 2 MWp per application) and sells power to the DISCOM at a state-determined tariff. The farmer earns land lease income. This component is not about pumps, it is about decentralised solar generation. If you want to lease your farm land for a solar plant and earn rental income, Component-A is the route.

Component-B: Standalone Solar Pumps (Off-Grid)

Component-B is the most relevant for most small and medium farmers. It subsidises the complete replacement of diesel pumps (or the installation of new solar pumps where no pump exists) with standalone solar pump systems rated 0.5 HP to 7.5 HP.

The funding structure:

• Central government subsidy: 30% of benchmark cost
• State government subsidy: 30% of benchmark cost
• Farmer upfront contribution: 10% of benchmark cost
• Bank loan (NABARD / rural banks): 30% at concessional rates

The entire system (panels, pump controller, mounting structure, and submersible or surface pump) is covered under the benchmark cost. Installation is through empanelled vendors approved by the state nodal agency, and some solar EPCs run dedicated PM-KUSUM installation programmes that handle vendor empanelment and subsidy paperwork on the farmer’s behalf. Applications go through state agriculture department portals.

Component-C: Solarisation of Grid-Connected Pumps

Component-C covers solarisation routes for grid-connected agricultural pumps or feeders under the current implementing arrangements. The required equipment and approval path are project-specific. A Qbits on-grid model should not be specified until the implementing agency, electrical designer and current model documents support it.

The solar system is installed on farm land or building rooftops near the agricultural pump. The inverter feeds solar power to the agricultural feeder. The DISCOM either offsets the pump electricity charges (net metering) or purchases surplus power at a feed-in tariff (gross or net, depending on the state’s policy). Individual farmers with one pump connection, water user associations, and cooperatives are all eligible.

Sizing the Solar Array for Agricultural Pumps

Sizing the solar array correctly determines whether the pump runs through peak irrigation hours or falls short on cloudy days. The array must cover the pump’s daily energy demand within the available peak sun hours at the farm location.

Calculating Daily Energy Demand

Start with how many hours per day the pump runs and the electrical input power (from the Pump Sizing Triangle, Step 2).

• A 2 HP pump (1.86 kW input) running 8 hours per day consumes 14.9 kWh.
• A 5 HP pump (4.66 kW input) running 8 hours per day consumes 37.3 kWh.

Peak Sun Hours by Region

India’s peak sun hours range from 4.5 hours per day in the Gangetic plain and North-East to 5.5–6.0 hours in Rajasthan, Gujarat, and Telangana. Use location-specific data from the Solar Energy Centre / MNRE irradiation maps or NREL’s Global Solar Atlas.

For a conservative sizing exercise, use 4.5 peak sun hours and include a 20% system loss factor (cable losses, temperature derating at 45 °C, controller inefficiency). India’s irradiation data by district is publicly available from the NREL Global Solar Atlas and from MNRE’s Solar Radiation Resource Assessment stations.

Array Sizing Formula

Programme packages are specified in the relevant MNRE or state tender documents, and their array sizes can differ from the formula figure above because pump type, daily water volume and running hours differ. Ask the supplier for the array size, controller rating and daily water output in writing, and compare them with the formula result for your own duty.

For Component-C (grid-tied), the array is sized not to run the pump directly but to offset monthly electricity consumption from the DISCOM. A 5 HP pump consuming 900–1,100 kWh per month would ideally have a 5–7 kWp grid-tied solar system to offset 50–70% of those units, depending on state tariff and feed-in rate.

Submersible vs Surface Pump: Which Works Better on Solar

The pump type significantly affects how the solar system behaves. Submersible pumps (borewells) and surface centrifugal pumps have different electrical characteristics.

Submersible Pumps (Borewells)

Submersible pumps are the dominant type for agricultural irrigation in India, particularly in water-scarce states like Rajasthan, Maharashtra, Karnataka, and Telangana. The motor is submerged in water, which keeps it cool and allows sustained high-torque operation.

Electrically, submersible motors (single-phase for up to 2 HP, three-phase for 3–7.5 HP in most standard configurations) have a high starting torque requirement. Their inrush current at direct-on-line start can reach 7× rated current. A dedicated pump controller with VFD is strongly recommended. Solar pump packages for borewells typically include a three-phase AC submersible motor with a matching three-phase pump controller, even in the 1–2 HP range, because three-phase provides better starting characteristics.

Surface Centrifugal and Mono-Block Pumps

Surface pumps draw water from open wells, canals, ponds, or rivers. They are simpler to install and service. Mono-block pumps (where motor and pump are a single unit) are common in Maharashtra, Punjab, and UP for surface water sources.

Surface mono-block pumps in the 0.5–2 HP range are typically single-phase. The starting surge is lower (5–6×) than deep-well submersibles, but VFD control still protects the motor and extends its service life. For solar, the advantage of surface pumps is that they can operate at variable speeds without significant loss of efficiency, a VFD controller’s ability to vary pump speed with sunlight availability is well-matched to surface centrifugal pump curves.

On-Grid, Off-Grid, and Hybrid for Agricultural Pumps: The Trade-Off

Different farm situations call for different solar topologies. The right choice depends on grid availability at the farm, pump operating hours, water availability, and budget.

Pros and Cons by Topology

For most smallholder farmers without reliable grid supply (common in UP, Bihar, MP, Odisha, Jharkhand), Component-B standalone solar pumps are the most practical choice. For farms in Punjab, Haryana, Gujarat, and Maharashtra with stable agricultural feeder supply, Component-C grid-tied systems often deliver better ROI because they earn feed-in income and allow pump operation at any time.

Read the full on-grid vs hybrid decision guide for a detailed ROI comparison across all three topologies.

Common Mistakes When Buying a Solar Pump System

Even experienced EPC installers make errors on solar pump projects. These are the seven most frequent mistakes seen in the field across India.

• Mistake 2: Under-sizing the panel array: Selecting panels only for the motor’s shaft power (HP × 0.746) without adding efficiency losses and inrush headroom. The array must cover input power, not output shaft power. A 2 HP pump needs at minimum a 2.2–2.5 kWp array, not a 1.49 kWp array.

• Mistake 4: Purchasing an off-grid pump controller for a Component-C setup: Component-C requires a grid-tied inverter that complies with anti-islanding protection (anti-islanding), DISCOM interconnection standards, and net-metering regulations. A standalone pump controller cannot export power to the grid and is the wrong product for Component-C.

• Mistake 5: Neglecting dry-run protection: Borewell water levels drop seasonally. A pump running dry within seconds reaches dangerous motor temperatures. All quality pump controllers include dry-run protection through pressure or current sensing, always confirm this feature before purchase.

• Mistake 6: Skipping DISCOM approval for Component-C: Grid-tied solar systems require formal net-metering or gross-metering approval from the DISCOM before commissioning. Installing and operating without this approval risks system disconnection, fines, and ineligibility for feed-in credits. Follow the net metering application process fully before energisation.

• Mistake 7: Choosing a pump not matched to the borewell depth: Submersible pump head (metres of water column) must match the actual static water level plus friction losses in the rising main. A pump rated for 20 m head will deliver very low flow at 50 m depth. Always obtain a hydrogeological report or water level data before selecting the pump’s head rating.

Read the guide on solar inverter selection for the broader framework on inverter selection criteria that applies beyond pump applications.

KUSUM Component-B Application Process: Step by Step

Applying for KUSUM Component-B involves state-level agencies, not a central national portal. The process differs slightly across states but follows a common structure.

The 5-Step KUSUM Component-B Application Process

1. Identify the state nodal agency: Each state has a designated agency (state agriculture department, RREC, TEDA, MSEDCL solar division, etc.). Visit the state agriculture ministry website or check the MNRE KUSUM implementation page to confirm the current nodal agency and their application portal link.

2. Register on the state portal: Create an applicant account using your Aadhaar number and mobile. Upload land ownership documents (khasra-khatauni), bank account details, and a photograph of the existing diesel pump or borewell (if replacing an existing pump). New pump installations require proof of agricultural land use.

3. Select empanelled vendor: The state portal lists approved solar pump vendors. You cannot use an unapproved vendor and still claim the subsidy. Shortlist two or three vendors, compare their quoted prices against the state benchmark cost, and verify installation timelines and after-sales service coverage.

4. Pay 10% upfront and apply for bank loan: The state co-ordinates the bank loan through NABARD or designated rural banks. The bank disburses funds directly to the empanelled vendor after you sign the loan agreement. Your cash outflow is 10% of the benchmark cost.

5. Inspection and commissioning: The state agency inspects the installed system before releasing the central and state subsidy tranches to the vendor. Keep all documents, photographs, and commissioning reports. After successful inspection, the system is registered under the KUSUM beneficiary database.

Source - MNRE KUSUM Portal, 2026. Benchmark costs and subsidy ratios are notified annually; verify current rates with the state nodal agency before applying.

Where Qbits Fits in Solar Pump Setups

Qbits publishes grid-tied on-grid and hybrid inverter families, and its public documents do not describe a standalone solar-pump controller. For any KUSUM project, verify the current component rules, empanelment, pump/controller package and exact approved equipment through the official implementing route.

• Hybrid Inverters: Review current QBH model documents and confirm the exact battery, firmware, PV, backup-output, transfer, communication, warranty and project requirements in writing.
• String Sizing Calculator: Use this free tool to confirm your panel-string configuration matches the selected Qbits inverter’s MPPT voltage range before finalising the design.

EPCs sourcing pump-site inverters at scale can use the solar inverter manufacturers in India evaluation guide to check certification depth and service-network coverage before shortlisting a vendor for a multi-farm rollout.

Contact Qbits with the site, load, equipment and document details relevant to this guide. Confirm the responsible party, deliverable, commercial scope and response time after submission.

Where Solar Pump Buyers Often Get Stuck: And How to Avoid It

The final hurdle for most farmers and small EPC contractors on solar pump projects is the documentation and vendor matching process. Here is a practical summary of the key pitfalls at each stage.

• At purchase: Verify that the pump controller is MNRE-empanelled for KUSUM if you are claiming Component-B subsidy. Non-empanelled equipment, however technically sound, will not qualify for subsidy reimbursement.

• At installation: Confirm the solar panel array orientation is south-facing (or south-south-west for afternoon-peak applications). Shading from trees, structures, or overhead lines is the single biggest cause of poor standalone pump performance. A proper shading analysis should be part of every site survey.

• At commissioning: For Component-C, complete DISCOM net metering approval before energising the inverter. For Component-B, run the pump through a full dry-run cycle test before covering the borewell casing, confirm dry-run protection cuts out correctly before leaving the site.

• At maintenance: Check the pump controller’s MPPT tracking efficiency annually by reviewing the daily generation log. Most modern controllers have a mobile app or LED indicator panel. A declining generation trend often indicates panel soiling, not controller failure, clean the panels before replacing any electronics.

Read inverter maintenance best practices for India to understand the annual maintenance schedule that applies equally to pump controllers and grid-tied inverters.

Solar pumps are supported by the PM-KUSUM programme and by state-level schemes. A farmer who commits to the application process can reduce the upfront share substantially (central assistance of 30% of the benchmark cost, plus any state share, per the MNRE PM-KUSUM page), and the technology is proven. The key is choosing the right product for the right topology, sizing it correctly with the Pump Sizing Triangle, and following the DISCOM and state nodal agency approval process from the start.