How Many Amps Does 400W Xtreme RV Boat Heater Draw From 12V Battery Bank?

Updated 10/16/2025 | Published 09/30/2025

Question:

I’m worried about power draw. How many amps does this 400W unit actually use?

asked by: Linda

Expert Reply:

Good question, Linda. The Xtreme Heaters RV Basement and Boat Bilge Heater with Quick-Release Bracket 400 Watts # XH67FR pulls about 5.2 amps when running, with a brief startup inrush around 8 amps for a second or two. That’s well within what a 15A RV or dockside breaker can handle. Just avoid running it on the same circuit as heavy-draw items like space heaters or microwaves.

Do you plan to run it off shore power only, or are you considering a generator backup?

expert reply by: Andrew N

Linda

10/16/2025

That helps, thanks! I was just wondering: could I hook this to my inverter temporarily if I lose shore power overnight, or would that drain my batteries too fast?

Andrew N.

10/16/2025

@Linda That’s a smart question, Linda. Technically you could run it through an inverter, but it’s not ideal for long stretches. A 400W heater at 120V would pull about 33 amps from your 12V battery bank, plus inverter loss. So even a 100Ah lithium would only last a few hours. It’s best to keep this one on shore power or generator backup and let your inverter handle smaller 12V loads.