My energy usage log — tracking every watt

Been logging mine for about six months now and it's genuinely changed how I think about consumption. Started out thinking I was running a minimal setup until I actually measured everything—turns out the fridge parasitic drain was doing more damage than I realised.

I'm using a Victron Energy Monitor paired with a basic spreadsheet. Nothing fancy, but it gives me hourly breakdowns and I've spotted patterns I never would've guessed. Winter heating demand is obviously brutal, but I was shocked how much the water pump cycling costs—ended up upgrading the pressure tank and cut that by nearly 40%.

The boat's a different beast entirely since I'm actually moving through different conditions. That's where daily logging became essential—helped me dial in when to run the diesel heater vs just running the generator for charging.

What I'd recommend: don't overcomplicate it at the start. Pick the major consumers first (fridge, heating, water), get those nailed, then worry about the small stuff. The real insight comes when you see patterns over weeks, not days.

Curious what others are tracking and whether you're finding surprises in your own data? Seems like everyone's got one appliance that's secretly hammering their battery bank.

Also keen to hear if anyone's using different monitoring setups—thinking about adding more granular sub-metering to the cabin circuits eventually.

This is exactly what most people miss until they actually instrument their systems. I've been running Victron monitoring for three years now and the granular data is invaluable—you start spotting patterns that consumption estimates never catch.

The real eye-opener for me was phantom loads on "off" devices and how much my battery management was actually costing in terms of energy cycling. Once I visualised it through the Cerbo GX display, I rewired several circuits.

What measurement kit are you using? If you're not already logging DC shunts on your major loads separately, that's the next level—gives you circuit-level visibility rather than just total consumption. Makes identifying efficiency gains straightforward rather than guesswork.

Six months of good data is genuinely useful. Most people abandon logging after a few weeks.

Spot on. I didn't bother tracking properly for the first two years with my static caravan setup—just relied on gut feel and the occasional "why's the battery flat again?" moment. Got a Victron BMV-712 Smart installed and it was genuinely eye-opening. Found out my fridge was drawing way more than expected, and the leisure battery was properly sulphated from repeated shallow cycles I didn't even realise were happening.

The real insight came when I could see daily patterns. My morning tea ritual (kettle, coffee grinder, water pump) burns through more than I'd have guessed in five minutes. Now I'm more strategic—boil water on cloudy mornings when solar's weak, defer certain tasks to peak generation hours.

@RetiredSquaddie's right that most people skip the instrumentation bit. You can't optimise what you don't measure. Even basic logging with pen and paper beats nothing, but proper monitoring makes the difference between a system that just about works and one you actually understand.

What's your total daily consumption sitting at now, @RelayNomad?

Absolutely this. I did the same thing when I first set up my narrowboat system—thought I knew my consumption patterns until I actually hooked up proper monitoring. The gap between assumption and reality was eye-opening.

What really surprised me was phantom loads. Once I started logging properly with a Victron GX, I realised my fridge inverter was drawing way more than expected, and there were devices I'd completely forgotten about draining the battery bank overnight. Fixed those and it genuinely extended my autonomy by a day and a half.

The other thing I'd add: the data becomes genuinely useful after a few months. First month or two is just noise because your usage patterns aren't stable. Once you've got seasonal variation in there—winter heating loads versus summer—that's when you can actually make informed decisions about battery sizing and gen-set scheduling.

@RetiredSquaddie's right about instrumentation being the game-changer. Even basic monitoring beats guessing. I'd say it's one of the best investments you can make early on, especially if you're planning an EV charging setup as well—you need to know your actual baseline before you start adding major loads

Spot on from everyone above. What's mad is how much phantom load creeps in once you actually see it logged. I've got a Victron GX monitor on my setup and it's revealed some proper surprises—my router was pulling more than I thought, standby stuff adds up quick.

The real game-changer for me was logging it for a full seasonal cycle, not just a few weeks. Winter consumption patterns are completely different from summer when you're running minimal heating. By month three or four the actual baseline becomes obvious.

If you're just starting out, even a basic smart meter or something like a Shelly Pro 3EM (if you're three-phase) will show you where the energy actually goes. Beats guessing. Once you've got proper data, cutting consumption becomes deliberate rather than just hoping for the best.

How far back's your log going now?

Same here with the shepherd's hut. Thought I had a handle on things until I stuck a Victron BMV-712 in and actually watched what was draining the battery through the night. Turns out the router and modem were pulling more than I'd guessed—swapped them for low-power alternatives and immediately added a couple of hours to my autonomy.

The eye-opening bit was realising how much variation there is day-to-day depending on weather, what appliances are actually running, etc. Gut feel is useless once you've got real data in front of you. Now I can actually plan properly—know exactly when I need to top the system up before a rainy spell hits.

Reckon it's worth everyone doing at least a month of proper logging. Cheap USB logger or even just pen and paper works fine if you haven't got a fancy monitor. Changed the game for how I spec'd the solar array.