<p>Algal Membrane Photobioreactors (AMPBRs) have demonstrated potential in treating domestic wastewater (WW) and greywater (GW). However, direct performance comparisons between these two types of water have not been thoroughly investigated. This study aims to evaluate and compare the energy efficiency and treatment performances of AMPBR systems in treating domestic WW and GW. Two laboratory-scale AMPBR reactors were operated continuously for 50 days, treating synthetic WW and GW. The reactors maintained a consistent hydraulic residence time (HRT) of 7 days and a flux rate of 100 L/m²/d, operating under a 12-h light/dark cycle without external aeration. The AMPBR treating wastewater (AMPBR-WW) achieved 95.8% COD removal and 96% BOD removal, while the AMPBR treating greywater (AMPBR-GW) achieved 90.9% COD removal and 90.2% BOD removal, respectively. The effluent BOD of AMPBR-WW exceeded reuse standards towards the end, whereas AMPBR-GW consistently remained below the desired wastewater reuse standards. The AMPBR-WW system achieved a total nitrogen (TN) removal rate of 60% and a total phosphorus (TP) removal rate of 41.7%. The GW-AMPBR system exhibited higher removal efficiencies with 82% TN and around 62% TP removals. Algal biomass production was significantly greater in AMPBR-GW, with an average concentration of 36.6 mg/L/d, compared to 16.6 mg/L/d in AMPBR-WW, suggesting a more significant potential for biomass production in GW treatment than in WW treatment. AMPBR-WW experienced consistent (nine times over 50 days) and frequent (1.28 times per week) fouling, whereas AMPBR-GW showed a gradual transmembrane pressure (TMP) increase, fouling only once at the end, with a fouling frequency of 0.14 times per week. The estimated net energy ratio (NER) was higher for AMPBR-GW (NER = 0.78) compared to AMPBR-WW (NER = 0.32). Overall, AMPBR-GW outperformed AMPBR-WW regarding energy efficiency, fouling frequency, and biomass production.</p>