oh my gosh. 
i explicitly not asked for a complete solution! thanks a bucket, there's a lot to learn for me in there.. 
i already had figured i'd need jsonata, but just couldn't wrap my head around it that far yet..
for anyone finding oneself in the same boat i need to add that this multi-sensor-object isn't coming from the efergy-api (which is used in the original flow i linked) but via energyhive - no idea how these two are related, but one can input one's efergy api key there and it just works.
here's the working flow with the energyhive url (anonymised and slightly commented):
kudos again @E1cid
[
{
"id": "eed469f0.42ac78",
"type": "tab",
"label": "efergy",
"disabled": false,
"info": ""
},
{
"id": "4fdaa584.be8fbc",
"type": "inject",
"z": "eed469f0.42ac78",
"name": "",
"topic": "",
"payload": "",
"payloadType": "date",
"repeat": "10",
"crontab": "",
"once": false,
"onceDelay": 0.1,
"x": 150,
"y": 140,
"wires": [
[
"3120ec7f.05a454"
]
]
},
{
"id": "3120ec7f.05a454",
"type": "http request",
"z": "eed469f0.42ac78",
"name": "Energyhive Data",
"method": "GET",
"ret": "obj",
"paytoqs": false,
"url": "http://www.energyhive.com/mobile_proxy/getCurrentValuesSummary?token=API_KEY_HERE",
"tls": "",
"persist": false,
"proxy": "",
"authType": "",
"x": 150,
"y": 320,
"wires": [
[
"5dd89e46.e7f8f",
"54e73801.e10948"
]
]
},
{
"id": "5dd89e46.e7f8f",
"type": "split",
"z": "eed469f0.42ac78",
"name": "",
"splt": "\\n",
"spltType": "str",
"arraySplt": 1,
"arraySpltType": "len",
"stream": false,
"addname": "",
"x": 350,
"y": 320,
"wires": [
[
"a6929417.921908"
]
]
},
{
"id": "f0d60938.6bc4c8",
"type": "inject",
"z": "eed469f0.42ac78",
"name": "test input",
"topic": "",
"payload": "[{\"cid\":\"PWER\",\"data\":[{$string($millis()+1000):$round(($random()*100)+50)}],\"sid\":\"xxx489\",\"units\":\"W\",\"age\":1},\t{\"cid\":\"PWER\",\"data\":[{$string($millis()+2000):$round(($random()*100)+100)}],\"sid\":\"xxx002\",\"units\":\"W\",\"age\":6},\t{\"cid\":\"PWER\",\"data\":[{$string($millis()-1000):$round(($random()*100)+300)}],\"sid\":\"xxx776\",\"units\":\"W\",\"age\":3}]",
"payloadType": "str",
"repeat": "",
"crontab": "",
"once": false,
"onceDelay": 0.1,
"x": 140,
"y": 440,
"wires": [
[
"5dd89e46.e7f8f"
]
]
},
{
"id": "a6929417.921908",
"type": "change",
"z": "eed469f0.42ac78",
"name": "",
"rules": [
{
"t": "set",
"p": "topic",
"pt": "msg",
"to": "payload.sid",
"tot": "msg"
},
{
"t": "set",
"p": "timestamp",
"pt": "msg",
"to": "$number($keys(payload.data[0]))",
"tot": "jsonata"
},
{
"t": "set",
"p": "payload",
"pt": "msg",
"to": "$$.payload.data[0].* / 1000",
"tot": "jsonata"
}
],
"action": "",
"property": "",
"from": "",
"to": "",
"reg": false,
"x": 500,
"y": 320,
"wires": [
[
"ca8db539.c77878",
"9563c7fd.288608",
"9ae410e2.ed5b2"
]
]
},
{
"id": "ca8db539.c77878",
"type": "ui_chart",
"z": "eed469f0.42ac78",
"name": "Efergy - Chart",
"group": "cc3cfa1e.bf5538",
"order": 1,
"width": 0,
"height": 0,
"label": "Efergy - Chart",
"chartType": "line",
"legend": "false",
"xformat": "h:mma",
"interpolate": "linear",
"nodata": "waiting for inject...",
"dot": false,
"ymin": "",
"ymax": "",
"removeOlder": "1",
"removeOlderPoints": "500",
"removeOlderUnit": "86400",
"cutout": "",
"useOneColor": false,
"colors": [
"#1f77b4",
"#aec7e8",
"#ff7f0e",
"#2ca02c",
"#98df8a",
"#d62728",
"#ff9896",
"#9467bd",
"#c5b0d5"
],
"outputs": 1,
"x": 960,
"y": 440,
"wires": [
[]
]
},
{
"id": "9563c7fd.288608",
"type": "switch",
"z": "eed469f0.42ac78",
"name": "",
"property": "topic",
"propertyType": "msg",
"rules": [
{
"t": "eq",
"v": "xxxxxx",
"vt": "str"
},
{
"t": "eq",
"v": "yyyyyy",
"vt": "str"
},
{
"t": "eq",
"v": "zzzzzz",
"vt": "str"
}
],
"checkall": "true",
"repair": false,
"outputs": 3,
"x": 670,
"y": 320,
"wires": [
[
"d042ac94.a7119",
"34510d6c.3f9972"
],
[
"efc70c61.4ebf2",
"ca23b520.f01ff8"
],
[
"6e2fb4a3.e5e79c",
"46223571.5bc22c"
]
]
},
{
"id": "f1a8c78.84aa238",
"type": "inject",
"z": "eed469f0.42ac78",
"name": "reset chart",
"topic": "",
"payload": "[]",
"payloadType": "json",
"repeat": "",
"crontab": "",
"once": false,
"onceDelay": 0.1,
"x": 500,
"y": 440,
"wires": [
[
"ca8db539.c77878"
]
]
},
{
"id": "d042ac94.a7119",
"type": "ui_text",
"z": "eed469f0.42ac78",
"group": "cc3cfa1e.bf5538",
"order": 3,
"width": 0,
"height": 0,
"name": "Efergy - Time Stamp",
"label": "Efergy - {{msg.topic}}",
"format": "{{msg.timestamp| date : \"h:mma\"}}",
"layout": "col-center",
"x": 980,
"y": 200,
"wires": []
},
{
"id": "efc70c61.4ebf2",
"type": "ui_text",
"z": "eed469f0.42ac78",
"group": "cc3cfa1e.bf5538",
"order": 5,
"width": 0,
"height": 0,
"name": "Efergy - Time Stamp",
"label": "Efergy - {{msg.topic}}",
"format": "{{msg.timestamp| date : \"h:mma\"}}",
"layout": "col-center",
"x": 980,
"y": 280,
"wires": []
},
{
"id": "6e2fb4a3.e5e79c",
"type": "ui_text",
"z": "eed469f0.42ac78",
"group": "cc3cfa1e.bf5538",
"order": 7,
"width": 0,
"height": 0,
"name": "Efergy - Time Stamp",
"label": "Efergy - {{msg.topic}}",
"format": "{{msg.timestamp| date : \"h:mma\"}}",
"layout": "col-center",
"x": 980,
"y": 360,
"wires": []
},
{
"id": "34510d6c.3f9972",
"type": "ui_gauge",
"z": "eed469f0.42ac78",
"name": "Efergy - Reading",
"group": "cc3cfa1e.bf5538",
"order": 2,
"width": 0,
"height": 0,
"gtype": "gage",
"title": "Efergy - {{msg.topic}}",
"label": "",
"format": "{{value}} KW",
"min": "0",
"max": "3.2",
"colors": [
"#00ff00",
"#ffff80",
"#ca3838"
],
"seg1": "",
"seg2": "",
"x": 970,
"y": 240,
"wires": []
},
{
"id": "ca23b520.f01ff8",
"type": "ui_gauge",
"z": "eed469f0.42ac78",
"name": "Efergy - Reading",
"group": "cc3cfa1e.bf5538",
"order": 4,
"width": 0,
"height": 0,
"gtype": "gage",
"title": "Efergy - {{msg.topic}}",
"label": "",
"format": "{{value}} KW",
"min": "0",
"max": "3.2",
"colors": [
"#00ff00",
"#ffff80",
"#ca3838"
],
"seg1": "",
"seg2": "",
"x": 970,
"y": 320,
"wires": []
},
{
"id": "46223571.5bc22c",
"type": "ui_gauge",
"z": "eed469f0.42ac78",
"name": "Efergy - Reading",
"group": "cc3cfa1e.bf5538",
"order": 6,
"width": 0,
"height": 0,
"gtype": "gage",
"title": "Efergy - {{msg.topic}}",
"label": "",
"format": "{{value}} KW",
"min": "0",
"max": "3.2",
"colors": [
"#00ff00",
"#ffff80",
"#ca3838"
],
"seg1": "",
"seg2": "",
"x": 970,
"y": 400,
"wires": []
},
{
"id": "9ae410e2.ed5b2",
"type": "debug",
"z": "eed469f0.42ac78",
"name": "",
"active": false,
"tosidebar": true,
"console": false,
"tostatus": false,
"complete": "false",
"x": 950,
"y": 540,
"wires": []
},
{
"id": "54e73801.e10948",
"type": "debug",
"z": "eed469f0.42ac78",
"name": "",
"active": false,
"tosidebar": true,
"console": false,
"tostatus": false,
"complete": "false",
"x": 390,
"y": 140,
"wires": []
},
{
"id": "6b7d215d.d3dab",
"type": "comment",
"z": "eed469f0.42ac78",
"name": "set SIDs",
"info": "set sensor's IDs here (sid)\n\nfor a different number of sensors add or remove outputs",
"x": 680,
"y": 280,
"wires": []
},
{
"id": "51b017de.788378",
"type": "comment",
"z": "eed469f0.42ac78",
"name": "set API key",
"info": "efergy API keys are working with energyhive\nhttp://www.energyhive.com/content/about/develop\n\nsee:\n\n_IMPORTANT: We continue to support existing energyhive customers but no longer sell this product.\n_\nsource: http://www.energyhive.com/content/products",
"x": 120,
"y": 280,
"wires": []
},
{
"id": "cc3cfa1e.bf5538",
"type": "ui_group",
"name": "Energy",
"tab": "41e12c54.3109b4",
"order": null,
"disp": true,
"width": "6"
},
{
"id": "41e12c54.3109b4",
"type": "ui_tab",
"name": "Home",
"icon": "dashboard",
"order": "1"
}
]