Full-load simulation is the moment of truth for any photovoltaic installation. Module datasheets, inverter efficiency curves and simulation software can only take a project so far — at some point the hardware has to be pushed to 100 % of its rated output, continuously, under controlled conditions, and watched. That is exactly what a load bank does. It converts electrical energy into heat (or regenerates it back to the grid) so that a PV inverter, a string combiner, a DC optimiser or an entire grid-tied array can be run at nameplate load without any real irradiance, any real load, and any weather dependency.
Over the past eighteen months our test laboratory has evaluated load banks from five manufacturers against a common solar-specific test matrix: DC-side string characterisation, MPPT tracking verification, inverter AC full-load burn-in, power factor and reactive capability checks, and step-response behaviour under cloud-transient emulation. This article summarises what we measured, what mattered, and which five units we would shortlist for different solar applications.
Note on data: all figures below come from our own bench configuration at 25 °C ambient unless otherwise stated. Manufacturer specifications should always be confirmed directly before purchase — configurations, options and firmware change frequently, and a load bank is only as accurate as the calibration certificate that ships with it.
Why Full-Load Simulation Matters for Solar PV Systems
A solar inverter spends most of its life at part load. That is precisely why full-load testing is not optional. Several failure modes only appear when the equipment is thermally soaked at rated current:
- Thermal design margins. IGBT junction temperatures, DC-link capacitor ripple and magnetics losses all scale non-linearly. A unit that runs clean at 60 % load can derate, trip on over-temperature, or lose efficiency badly at 100 %.
- MPPT behaviour at the array's true operating point. Maximum power point tracking is easy to verify on a bench with a stable electronic source; it is much harder to verify when the input is being swept and the load is pulling hard.
- Protection coordination. Over-current, over-voltage, anti-islanding and DC insulation monitoring thresholds must be proven at the same time as the thermal stress, not separately.
- Grid-code compliance. Reactive power capability, power factor range (typically 0.8 leading to 0.8 lagging), voltage/frequency ride-through and harmonic injection all require a load that can absorb real power and, for some tests, reactive power simultaneously.
- Warranty and due-diligence evidence. EPCs, insurers and lenders increasingly want full-load test reports, not just factory acceptance sheets.
The load bank is therefore a metrology instrument as much as a heat sink. Its kW accuracy, resolution, stability and repeatability directly determine whether the numbers in your test report mean anything.
How We Tested: Bench Setup and Pass/Fail Criteria
Every candidate was evaluated on the same rig: a 100 kW three-phase grid-tied PV inverter on the AC side, a programmable PV simulator on the DC side, a Class 0.2 power analyser on both ports, and calibrated thermal logging at the intake and exhaust. DC candidates were tested against a 30 kWp string emulation with programmable I-V curves including temperature coefficients and partial shading profiles.
The scoring criteria were deliberately weighted toward what solar testing actually demands:
| Criterion | Why it matters for PV | Weight |
|---|---|---|
| Load step resolution | Needed to sweep the inverter across its MPPT window in fine increments | 20 % |
| Power accuracy & stability | Determines the validity of efficiency and derating measurements | 20 % |
| Duty cycle / continuous rating | Burn-in runs are measured in hours, not minutes | 15 % |
| Control interface & automation | Scripted cloud-transient and ramp profiles | 15 % |
| Reactive / regenerative capability | Grid-code and power factor testing; energy cost | 15 % |
| Footprint, cooling, noise, serviceability | Site and factory constraints | 15 % |
1. Avtron ADDERS Series — Best for Inverter AC Full-Load and Grid-Code Testing
The Avtron ADDERS family is the closest thing to an industry default for medium-voltage and low-voltage AC load testing, and it held up well on the solar side. The units are modular: resistive elements handle real power, optional reactive element banks add inductive or capacitive loading, giving the 0.8 leading to 0.8 lagging range that most grid codes now ask for.
What we measured. On a 500 kW frame in resistive-only mode, we recorded load stability within roughly ±1 % of setpoint once thermally settled, with step resolution down to about 1 kW on the smallest element group — fine enough to walk an inverter through its entire operating window. Reactive capability tracked the commanded power factor closely enough that our power-factor sweep (0.8 lag → 1.0 → 0.8 lead) produced a clean, monotonic response with no hunting.
What we liked. The step control is genuinely granular rather than a coarse ladder of binary steps, so you can hold a target load through small supply fluctuations. Control is available locally, via PLC/Modbus, and through vendor software, which made scripted ramp profiles straightforward. Build quality is clearly aimed at twenty-year service life, and the resistive element replacement procedure is a field job, not a factory return.
What to watch. These are not cheap, and the reactive option materially increases both price and lead time. Outdoor medium-voltage configurations also need real estate and proper intake/exhaust planning — recirculation will cost you accuracy and, eventually, elements.
Verdict. The reference choice when the test objective is inverter AC-side full-load burn-in with reactive capability and formal grid-code evidence.
2. Crestchic Containerised Load Banks — Best for Utility-Scale and On-Site Plant Testing
When the array is measured in megawatts and the inverter station is already installed on site, you are not looking for a bench instrument — you are looking for a containerised load bank that arrives on a trailer, is wired into the MV/LV panel, and runs for a full day. Crestchic's containerised units are built for exactly that workflow, and their resistive-reactive variants cover the reactive testing that utility interconnection studies increasingly require.
What we measured. On a 1 MW containerised frame we ran a six-hour continuous soak at 100 % resistive load with ambient swinging from 12 °C to 31 °C. Output held steady with no derating and no element failure. Step response to a commanded 25 % load increase settled within a couple of seconds — not as fast as an electronic load, but entirely adequate for inverter load-following tests. Noise was the expected trade-off: forced-air cooling at full duty is loud enough that hearing protection and a clear exclusion zone are mandatory.
What we liked. Transport, lifting points, cable entry and control provisions are all designed by people who have actually commissioned plant sites. The control system supports networked multi-unit operation, which lets you build 2 MW, 5 MW or higher capacity from standard modules instead of ordering a bespoke frame. Service access to elements and contactors is generous.
What to watch. Planning permission, fuel or cable logistics, and site access all become project tasks. Smaller PV testing labs will find the granularity too coarse — the smallest step on a large container is bigger than some inverters' entire rating band.
Verdict. The right tool for commissioning and capacity testing of utility-scale PV plants, particularly where grid-code reactive testing must be documented on site.
3. Simplex Swift-E — Best Portable Resistive Unit for Small PV and Field Work
Most rooftop and C&I installers do not need megawatts. They need something that fits in a van, plugs into a three-phase distribution board, and can prove a 30 kW or 100 kW inverter delivers full output. The Simplex Swift-E range is designed for that niche and it is the unit we reach for when a test must happen at a customer site rather than in the lab.
What we measured. On a 100 kW frame we found the load step granularity coarse relative to the lab units — usable for verifying full-load capability and for stable multi-hour runs, but not for fine efficiency mapping. Accuracy was good once airflow was unobstructed: our readings drifted noticeably when we accidentally placed the unit too close to a wall and the exhaust recirculated. That is a user error, but it is a very common one on site.
What we liked. Forklift pockets, castors, a compact footprint and a straightforward local control panel. Operators who have never used a load bank before can be trained in ten minutes. Cable sets and distribution options are well thought through. For a commissioning crew moving between sites, the logistics savings are the real benefit.
What to watch. Resistive only — no reactive testing. Not intended for DC string characterisation. Continuous rating is honest but requires clean, cool intake air; in a plant room in summer you will lose headroom.
Verdict. Excellent value for rooftop and C&I commissioning, factory acceptance of small inverters, and field verification of nameplate output.
4. EA Elektro-Automatik EA-PSB 10000 — Best Bidirectional DC Load for Inverter and Storage Testing
On the DC side of a PV system the test requirement changes completely. You are no longer dumping heat; you are emulating an array, or absorbing the output of a DC source, with programmable precision. The EA-PSB 10000 series is a bidirectional DC power supply and electronic load in one chassis, which makes it unusually well suited to modern PV-plus-storage architectures.
What we measured. Load regulation was tight across the full range, and the instrument's ability to switch seamlessly between sourcing and sinking made short-duration charge/discharge cycling tests on hybrid inverters essentially a scripting exercise rather than a hardware reconfiguration. Programmable I-V curves let us emulate a PV string at different irradiance and cell temperatures, including the knee behaviour that matters for MPPT verification. Sink-mode energy recovery back to the grid kept the lab cool and the electricity bill sane — over a week of continuous cycling, that is a
