Nowadays,　the　transcritical　CO2　heat　pump　water　heater　is　widely　used　for　hot　water　production.　However,　the　larger　pressure　difference　of　the　basic　system　leads　to　the　huge　throttling　loss,　which　will　significantly　worsen　the　system　performance.　The　ejector-expansion　method　accompanied　by　the　internal　heat　exchanger　is　an　effective　way　to　reduce　the　throttling　irreversibility.　Nevertheless,　the　CO2　ejector-expansion　system　is　seldom　studied　with　the　exergy　analysis,　including　the　exergo-economic　and　exergo-environmental　analysis.　In　this　paper,　this　system　is　theoretically　evaluated　from　comprehensive　perspectives　with　emphasis　on　the　exergy　analysis　and　the　sensitivity　analysis　of　ejector　cost　and　electricity　price　is　also　conducted.　Results　show　that　with　the　ejector　and　internal　heat　exchanger,　the　coefficient　of　performance　is　improved　by　7.38%　and　pressure　ratio　will　reduce　to　2.66　with　the　ejector　efficiencies　of　0.90.　Furthermore,　the　exergy　destruction　of　the　throttling　value　could　be　reduced　by　95.38%-98.76%,　leading　to　the　increased　exergy　efficiency.　The　largest　temperature　matching　factor　is　achieved　by　the　basic　system　with　the　internal　heat　exchanger.　The　cost　rate　of　the　throttling　valve　and　cost　per　unit　of　exergy　production　is　reduced　by　85.65%　and　0.42　CNYMJ−1,　respectively.　Moreover,　the　maximum　pollutant　emission　reduction　is　115.41　tons,　which　results　in　the　lowest　specific　exergo-environmental　cost　of　1.95　CNY⋅(kW⋅h)−1　in　the　proposed　system.　©　2022