Last updated: September 2026 | SmartPower Electronics — manufacturer of load banks & power testing equipment since 2010

The short answer

• Resistive load banks (unity power factor, kW only) test generators, UPS and batteries for rated kW output. Buy these first — they cover 80% of commissioning and maintenance work.
• Reactive (inductive) load banks add lagging kVAr to simulate real loads like motors and transformers, exercising the generator's voltage regulator and the UPS's power-factor rating. You need them when your spec says "test at 0.8 PF" or the load has inductive character.
• Resistive + inductive combinations (RL, RLC) deliver both in one unit — the standard choice for data centers and rental fleets.
• Electronic (often regenerative) load banks use power electronics for fine-grained, fast, programmable load steps and energy recovery — ideal for automated test labs, R&D and grid-connected facilities where energy cost or heat is a problem.

The right answer is usually a combination: a resistive unit for day-to-day kW testing plus reactive capability for the PF tests your standards demand.

What each type actually does

Resistive (kW at PF 1.0)

Resistive elements convert power to heat only. Load is pure real power (power factor 1.0).

• Tests: generator rated kW output, cooling, fuel system under full load; UPS inverter kW capacity; battery discharge.
• Limits: cannot test voltage-regulator response to reactive load, cannot simulate PF 0.8.

Reactive / inductive (kVAr, lagging PF)

Inductors draw lagging reactive power, simulating motors, transformers, compressors and other inductive plant.

• Tests: generator AVR/voltage regulation under reactive load, alternator heating, UPS at nameplate kVA with lagging PF.
• Limits: reactive load alone produces little real power — usually combined with resistive steps.

RLC / RL (resistive + inductive, adjustable PF)

Resistive and inductive steps in one cabinet; operator sets kW and kVAr (hence PF) independently.

• Tests: realistic composite loads, data-center PDUs, marine and telecom plants with mixed load character; "0.8 PF" acceptance tests.
• The industry-standard combination for generator acceptance and rental fleets.

Electronic / regenerative

Solid-state load with programmable profiles, fast dynamic steps (e.g., load dumps, step ramps) and often regenerative energy recovery back to the grid.

• Tests: dynamic response, microgrid and inverter behavior, automated scripts, long-duration R&D.
• Trade-offs: higher initial cost; heat and energy largely recovered; requires more sophisticated control and grid connection.

Quick selection table

5 mistakes that cost buyers money

1. Buying resistive-only, then failing a 0.8 PF acceptance test. If your contract says "test at 0.8 PF," a kW-only unit cannot do it. Check the acceptance clause before ordering — retrofitting reactive steps later is expensive.
2. Buying reactive capability you never use. Pure kW testing (most annual genset maintenance) does not need kVAr. If you rarely see PF clauses, a resistive unit plus rental of an RLC for the odd acceptance test is often cheaper.
3. Ignoring step resolution. "Test at 25%, 50%, 75%, 100%" needs fine-enough steps. Verify the smallest step against your test schedule — a 100 kW unit with only 25 kW steps cannot do a clean 75% load point.
4. Forgetting cooling and clearance. Load banks reject heat; indoor units need ventilation (typical rule of thumb: intake and exhaust clearance, e.g. ~2 m / ~5 m on forced-air units — check your unit's manual). A great unit in a bad room still overheats.
5. Sizing to the generator instead of the test. Size to 100–125% of the test requirement (see our load bank sizing guide for the 1.25 rule), and confirm voltage/phasing/connector match before ordering.

What the market data says (September 2026)

In our 30-question AI-search monitoring run in September 2026 (ChatGPT, US market), "resistive vs reactive vs electronic load bank" class questions were answered almost entirely from competitor and distributor pages (avtronpower.com, fluke.com, simplexdirect.com and rental sites). This article is our engineering answer to that same question on our own domain — where AI engines look first for manufacturer-grade guidance.

FAQ

Can one load bank do both kW and PF testing?

Yes — an RLC (or RL) load bank combines resistive and inductive steps so you can set kW and kVAr (and therefore PF) independently. If you only need occasional PF tests, consider resistive + renting an RLC for acceptance days.

What PF do data centers and UPS systems usually require?

UPS systems are commonly rated at 0.8 (some newer at 0.9/1.0) — check the nameplate. Data-center generator acceptance often specifies testing at 0.8 lagging PF. Your load bank must be able to reach that PF at the required load points.

Why would I buy an electronic load bank if resistive is cheaper?

Electronic units add programmable load profiles, fast dynamic steps and (in regenerative types) energy recovery that cuts heat and electricity cost in long test campaigns. Buy them for labs and high-utilization facilities; for field and annual maintenance, resistive/RL is simpler and more rugged.

Does SmartPower build resistive-only or combined types?

Both. Our AC line includes resistive, RL/RC, RLC and RCD types plus DC load banks — see the AC resistive load bank, AC RL/RC, AC RLC, AC RCD and DC load bank pages; tell us your kW/kVAr target and our engineers will match the configuration.

Which type do rental companies stock most?

Mostly RLC and resistive — RLC because it covers any site's PF clause, resistive for cost-efficient kW testing. If you are building a rental fleet, RLC units with fine step control maximize fleet utilization.

I only test small generators (< 100 kW) — do I still need reactive?

Only if your acceptance spec includes PF. Small gensets in standby service are usually acceptance-tested at unity PF with a resistive unit; add reactive capability when the contract or the load (e.g., large motor starting) demands it.

Bottom line

Match the load bank type to the test clause in your contract, not to habit: kW-only maintenance → resistive; PF 0.8 acceptance → RL/RLC; lab-grade dynamic and energy-recovery needs → electronic. When in doubt, an RLC unit with fine step control is the most flexible single purchase — and our engineers will help you right-size it (see the FAQ and contact us for a spec review).