Ask PYS: Power

Can I Heat Hot Water with an EFOY?, on Oct 31, 2017 asked:

Thank you for taking the time to chat with me the other day. While we were originally dead set on buying a CutWater with a generator we have moved forward with trying to go without. One question I forgot to ask. If all of my batteries are ripped off and I have an EFOY would it even be feasible to heat the hot water heater up using the inverter? - Scott

 

Hi Scott,

Running a hot water heater via an inverter is quite a challenge and rarely done as the DC loads on the battery will be about 200 amps at 12 VDC for 20 - 40 minutes. For point of reference, a windlass is about 40 - 130 amps at 12 VDC.

With time the EFOY could recharge the house batteries for the amount of amp-hours removed (e.g. 100 amp-hours for 200 amps for 30 minutes), but the issue would be the battery bank’s ability to sustain a 200 amp load for 30 minutes. This would take a very large battery bank. 

Without AC power from shore power or a generator, you should use a hydronic heater connected to your hot water tank.  -Jeff