A demand-response system (1A, 1B, 1C) comprising: a first aggregator apparatus (10, 71, 310, 410) configured to perform a demand-response-related control of a first device group (100, 710, 500) including a first heat pump device (100a, 710a); a second aggregator apparatus (20, 72, 73, 320, 420) configured to perform a demand-response-related control of a second device group (200, 400, 600, 720, 730) being different from the first device group, the second aggregator apparatus being different from the first aggregator apparatus; and a first upper-tier aggregator apparatus (30, 50, 60, 430) configured to send a power adjustment request to the first aggregator apparatus and send another power adjustment request to the second aggregator apparatus, by using commands being common to the first aggregator apparatus and the second aggregator apparatus, wherein: the first aggregator apparatus is configured to perform the demand-response-related control of the first device group installed in a plurality of buildings in accordance with the power adjustment request; the second aggregator apparatus is configured to perform the demand-response-related control of the second device group installed in a plurality of buildings in accordance with the other power adjustment request; the first aggregator apparatus is configured to use first dedicated commands for the first device group to send a control instruction to the first device group in order to perform the demand-response-related control of the first device group; and the second aggregator apparatus is configured to use second dedicated commands for the second device group to send a control instruction to the second device group in order to perform the demand-response-related control of the second device group, characterized in that: the first dedicated commands are suitable for control specifications of the first device group, and the second dedicated commands are different from the first dedicated commands and suitable for control specifications of the second device group which are not identical to the control specifications of the first device group. a first aggregator apparatus (10, 71, 310, 410) configured to perform a demand-response-related control of a first device group (100, 710, 500) including a first heat pump device (100a, 710a); a second aggregator apparatus (20, 72, 73, 320, 420) configured to perform a demand-response-related control of a second device group (200, 400, 600, 720, 730) being different from the first device group, the second aggregator apparatus being different from the first aggregator apparatus; and a first upper-tier aggregator apparatus (30, 50, 60, 430) configured to send a power adjustment request to the first aggregator apparatus and send another power adjustment request to the second aggregator apparatus, by using commands being common to the first aggregator apparatus and the second aggregator apparatus, wherein: the first aggregator apparatus is configured to perform the demand-response-related control of the first device group installed in a plurality of buildings in accordance with the power adjustment request; the second aggregator apparatus is configured to perform the demand-response-related control of the second device group installed in a plurality of buildings in accordance with the other power adjustment request; the first aggregator apparatus is configured to use first dedicated commands for the first device group to send a control instruction to the first device group in order to perform the demand-response-related control of the first device group; and the second aggregator apparatus is configured to use second dedicated commands for the second device group to send a control instruction to the second device group in order to perform the demand-response-related control of the second device group, the first aggregator apparatus is configured to perform the demand-response-related control of the first device group installed in a plurality of buildings in accordance with the power adjustment request; the second aggregator apparatus is configured to perform the demand-response-related control of the second device group installed in a plurality of buildings in accordance with the other power adjustment request; the first aggregator apparatus is configured to use first dedicated commands for the first device group to send a control instruction to the first device group in order to perform the demand-response-related control of the first device group; and the second aggregator apparatus is configured to use second dedicated commands for the second device group to send a control instruction to the second device group in order to perform the demand-response-related control of the second device group, characterized in that: the first dedicated commands are suitable for control specifications of the first device group, and the second dedicated commands are different from the first dedicated commands and suitable for control specifications of the second device group which are not identical to the control specifications of the first device group.