I plan on installing a Echo 27 Tankless Water system but it requires 3 40 amp breakers. Can I install a sub panel to accommodate this and if so what size?

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    I'll let the electrical experts weight in on the details of subpanels, but that is a LOT of power. According to the spec sheet, it really draws 112.5 Amps at 240V. Are you sure you have enough power to spare in your utility service? – manassehkatz-Reinstate Monica May 6 '18 at 19:52
  • I’m not an electrical expert but I would guess around a 150 amp sub panel, since most residential panels are at most 200 amps, at least here in the States you won’t have much power left over. The reason it draws so much is it is trying to heat it from 50 degrees or so to 140 instantly. The gas equivalents usually take 200,000 btu instead of the traditional 40,000 btu for a 40 gallon water heater. – user76730 May 6 '18 at 20:15
  • If you need to add a sub-panel move lighter load circuits circuits like general plugs and lighting there. Put your large loads in the first main panel. It’s likely more economical to just upgrade the main panel to bigger. – Tyson May 6 '18 at 21:32
  • Sure, but the breaker serving the subpanel will be large and fairly expensive. But that's a fine way to run a single 2/0Al cable instead of three #8s. Price the cable both ways. Is your panel full? – Harper - Reinstate Monica May 6 '18 at 21:37
  • @user76730 because tanked heaters heat all day, but tankless only heat while a faucet is open. So they need lots of amps in that short moment. – Harper - Reinstate Monica May 6 '18 at 21:40

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