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Comment by FLHerne | Hacker News Reader

Not the poster, but I live off-grid on a boat in the UK and pretty much everything (including the laptop I'm commenting from) runs off 12V DC.

I have 800W of solar panels and a 3.5kWh LFP battery bank.

I use approximately 2kWh per day in summer, 1kWh in winter, 500Wh when it's cold enough that I can turn the fridge off.

In the summer I dump any excess to an immersion water heater.

At that level the self-consumption power of an inverter, about 5-10W, is significant so I avoid relying on it for anything powered all day (but it's useful for appliances, power tools and other intermittent items).

Using incredibly wasteful amounts of energy isn't necessary, people just do it.

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Unless there is some space/weight constraint, adding additional battery capacity for idle draw and running an inverter is likely less expensive than trying to find 12v only equipment.

OP is running sealed lead acid batteries, they could have 5-6x the capacity using LFP batteries with the same weight.

Space for panels is very constrained, they already get in the way more than I'd like.

I'll probably expand the battery bank at some point, but that only averages energy over a wider time period rather than increasing the total available.

I've spent very little on 12V equipment - my router and laptop are easily run off DC-DC supplies and USB supplies/lighting/water pumps/radios etc. are widely available. The only thing that's powered full-time and would have been significantly more expensive at 12V is the fridge, and I got that for free with an easily-replaced failed thermostat.

Doubling my present battery capacity would definitely cost more than I've spent on everything else.

In America, a 1,000 square foot home uses an average of 8x the energy you do during the summer. I find that amount to be somewhat lower than I expected to be if I’ll be honest. After all, America is the land of central air conditioning and clothes dryers.

I’m sure you’re aware of this already, but maybe it’s worth pointing out to people that changing your lifestyle to consume less doesn’t require boat life, van life, or tiny home life. A smaller conventional house and a more thoughtful use of your thermometer will go a long way. Hang up your clothes instead of putting in the dryer, as a bonus they’ll last way longer.

Why not use higher voltage, like 24 or 48V?

That's how it came, and while I've incrementally added or replaced a lot of things there's no point switching.

I would probably go with 24V if starting from scratch - there's a huge market of automotive and caravan parts that are 12/24V and generally don't support 48V.

If relying on an inverter more I might have a 48V main bank and run the low-voltage stuff off a DC-DC.

Why dumping the excess is needed?

It's not needed, but if the batteries are full the energy might as well go somewhere useful.

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