Simple categories matching efficient:

• creature,
• appliance,
• truck,
• meat,
• equipment,
• ionization,
• transport,
• container,
• facility,
• activity,
• institution,
• product,
• technology,
• service,
• vehicle,
• fuel,
• ballast,
• ministry,
• action,
• fixture,
• system,
• component,
• means,
• manner,
• item,
• gear,
• device,
• port,
• stove,
• measure,
• radiator,
• thing,
• business,
• energy,
• organization,
• unit,
• way,
• utility,
• process,
• laser,
• automobile,
• engine,
• performance,
• commodity,
• network,
• practice,
• machine,

Members with property efficient:

• pollution_control,
• refrigerator,
• dishwasher,
• laser,
• aaa_showerhead,
• recycling_program,
• fax_machine,
• coal,
• propane_gas,
• housing,
• clothes_washer,
• fridge,
• reflector,
• fuel-cell_technology,
• charcoal,
• transport,
• select_case,
• computer,
• advance_framing,
• old_refrigerator,
• washer,
• spray_foam,
• wall,
• sewerage_service,
• copier,
• natural_lighting,
• audit,
• light_fitting,
• data_evaluation,
• use,
• packed_tower,
• sun_oven,
• freezer,
• microwave,
• air-conditioning_system,
• biomass,
• oxygen_firing,
• hybrid_car,
• suv,
• alcohol,
• european_hatchback,
• image,
• battery,
• education,
• legal_sanction,
• home_insulation,
• mitosis,
• stove,
• lighting_system,
• reaper,
• combined_heat,
• fluorescent_lighting,
• nuclear_fusion,
• maintenance_equipment,
• boiler_control,
• truck,
• coke,
• river_transport,
• photoelectric_cell,
• fish,
• cavity-wall_insulation,
• concern,
• organic_poultry,
• drive,
• taxi_service,
• semiconductor_laser,
• pickup,
• change_control,
• electric_car,
• electronic_ballast,
• light,
• country,
• oxidation,
• tube_light,
• cycle,
• cell_growth,
• blast-furnace_operation,
• demand,
• petroleum,
• fluorescent_light,
• transformer,
• savannah_lion,
• maritime_transport,
• water-heater_blanket,
• plumbing,
• hybrid_vehicle,
• mixer,
• boiler,
• tray_aerator,
• co2_laser,
• hybrid_truck,
• geothermal_heating,
• infusion_pump,
• bulldozer,
• shower,
• liquid_petroleum,
• incremental_technology,
• boost,
• singing_competition,
• light_truck,
• bus,
• ice,
• health-care_system,
• office_automation,
• tractor_means,
• fax,
• railcar,
• sport,
• rain_sensor,
• theoretical_preparation,
• solar_panel,
• light_fixture,
• lighting_control,
• solid_fuel,
• fda,
• myosin_motor,
• corporation,
• social_tie,
• worm,
• wall_insulation,
• waterless_urinal,
• specialized_equipment,
• design,
• control,
• internet,
• printer,
• web_interface,
• shower_head,
• administration,
• exercising,
• toaster,
• interpretation,
• van,
• christian_education,
• nanotechnology,
• loft,
• fluorescent,
• bowl,
• switch,
• educational_office,
• military,
• air-conditioner_window,
• joint_service,
• thermal_cracking,
• low_emission,
• modern_lighting,
• rocket_stove,
• range,
• pc,
• cabinet_cooler,
• pallet,
• thin_computer,
• lineage_pedigree,
• ventilation_fan,
• high_efficiency,
• rapid_custom,
• window,
• heat_transfer,
• evolution,
• efficient_lighting,
• increased_insulation,
• natural_landscaping,
• protocol,
• tongue,
• crossover_vehicle,
• room_service,
• car,
• storm_line,
• dryer,
• toilet,
• digital_circuit,
• motor,
• new_york,
• good_housekeeping,
• smart_car,
• office_equipment,
• fan,
• smart_meter,
• jackal_pup,
• turbine,
• holmium_laser,
• connector,
• electricity,
• oil,
• lighting_equipment,
• time_control,
• gas,
• small_suv,
• raising_hands,
• videotape,
• appliance,
• port,
• shovel,
• insulation,
• transport_service,
• cog,
• new_pc,
• english_corner,
• pump,
• natural_ventilation,
• power,
• natural_gas,
• fish_trap,
• phone,
• web_browsing,
• windows,
• analysis,
• bile_urchin,
• sun,
• showerhead,
• ash_particle,
• faucet,
• video,
• application_support,
• shielding,
• tunnel_washer,
• dimmer,
• certain_appliance,
• price_incentive,
• mail,
• agency_service,
• recycling,
• public_auction,
• telecommunication,
• cooling,
• training_service,
• contention,
• throughput_guideline,
• wind,
• office,
• compact_fluorescent,
• carbon-dioxide_laser,
• efficient_light,
• chainsaw,
• lcd_screen,
• enhancement_equipment,
• cooler,
• active_sport,
• ceiling_insulation,
• reading,
• dish,
• email,
• letter_writing,
• tv,
• double_facade,
• stock,
• timing_switch,
• sport-utility_vehicle,
• oven,
• sprinkler,
• laundry_service,
• drier,
• compact_vehicle,
• plane,
• net,
• coyote,
• golf_car,
• inverter,
• street,
• solar_system,
• carrier,
• instant_messaging,
• flow,
• discussion,
• kettle,
• service-station_lighting,
• glucose_metabolism,
• peer_control,
• kerosene,
• public,
• chalk,
• rail,
• modem,
• smaller_suv,
• sprinkler_irrigation,
• laser_ionization,
• loft_insulation,
• book_building,
• lighting,
• hydraulic_motor,
• courier_service,
• diesel,
• company,
• fuel-cell_vehicle,
• generator,
• chilean_port,