Depends on where. Almost no HHO users around here overall....most use Nat Gas or Propane (if in the boonies) at this point. I have nat gas. Considering how cold it has been the bills have not been bad at all thanks to a 93% efficiency furnace. I can only wonder what people with old draft 50-55% furances are forking out though. Not only are they 40%+ less efficient but that draft uses indoor air, thus pulling even more cold air in every crack in the house while its running..... $$$$$ Doubling the bill would not be pretty.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)