Tiny house emergency backup — is 5kWh enough to ride out a grid outage?

Been stress-testing my setup after a neighbour's place went dark for 18 hours during the January storms. My tiny house runs a Victron MultiPlus-II 3000/48V with a 5.12kWh Fogstar Drift 48V LiFePO4 pack, fed by 800W of Renogy panels on a 30° south-facing roof. Winter harvest here has been averaging a miserable 1.2–1.8kWh/day on overcast days.

The maths worry me. My actual measured daily consumption sits around 3.8kWh — induction hob, small fridge, laptop, LED lighting, a 300W oil-filled radiator running maybe 4 hours overnight. At 80% usable capacity that's roughly 4kWh from the Fogstar before the BMS cuts in, so I'm basically living on a knife edge once the grid drops and solar is flat. I can shed the hob and radiator easily enough, but even stripped back to essentials I'm pulling about 1.9kWh/day.

What I'm genuinely trying to work out is whether adding a second 48V 100Ah battery (another ~5kWh) is the right move, or whether a small propane backup generator wired through the Victron's AC input makes more sense for resilience. The generator route feels like it solves the problem faster — maybe a Honda EU22i or a Kipor — but it adds noise, maintenance, and fuel storage faff.

Has anyone here actually run through a 24–48 hour outage on a similarly sized system in winter? Curious what your real-world shed loads ended up being, and whether you leaned into more storage or a backup source.

@CrispyRoamer that January storm hit hard around here too — proper wake-up call.

5.12kWh should cover 18 hours in a tiny house, but only if you've actually mapped your overnight baseline load. My shepherd's hut surprised me when I did a proper audit — the propane fridge igniter, water pump cycling, and a single LED strip were quietly chewing through far more than I'd assumed.

The MultiPlus-II is brilliant at this — pull the VRM portal data and look at your overnight consumption graphs rather than guessing. Real numbers beat estimates every time.

One thing I'd flag: if you're running any resistive heating at all — even a small panel heater — that 5kWh disappears alarmingly fast. Passive insulation upgrades paid off more for my resilience than doubling battery capacity would have done.

HollyGraham87 | 📍 Welsh Borders | ⚡ 4.8kWh LiFePO4 + 800W solar

@CrispyRoamer I ran almost identical numbers last winter when we had a 22-hour outage here. The honest answer is it depends entirely on your loads — my 5kWh felt very comfortable because I'd already swapped to an induction hob with a gas backup and my fridge is a proper efficient 12V unit.

What's your heating situation? That's usually the killer. If you're running any electric heating at all, 5kWh disappears surprisingly fast.

One thing worth doing is pulling the consumption graphs from your Victron Cerbo/CCGX (assuming you have monitoring set up) and checking your actual overnight draw rather than estimating — the real figures are often quite different from what you'd expect. Made a big difference to my planning once I could see genuine patterns.

@CrispyRoamer in a shepherd's hut I've found the real killer is heating — even a small diesel or propane heater draws more than you'd think once you factor in the controls and ignition cycling.

5.12kWh at 80% usable DoD is roughly 4kWh in practice. If you're not running heating off the battery you're probably fine. If you are, that 18 hours could get tight by hour 14.

Worth logging your actual overnight draw for a few nights with Victron's VRM portal — the consumption graphs are dead useful for spotting surprise loads. Mine flagged that my water pump was cycling way more than I'd realised.

@CrispyRoamer the weak point nobody's mentioned yet — what's your recharge source during the outage? Solar's obviously useless at night and pretty grim in January even during the day.

I run a similar Victron setup as emergency backup and the battery alone buys me time, but I paired it with a small Honda generator as a fallback for extended outages. Even just 2-3 hours of genny time tops the pack back up nicely.

5kWh is fine if you're disciplined about loads. Kill anything with a heating element, drop the fridge to minimum, no kettle. Basically treat it like camping in your own home.

Worth checking your MultiPlus transfer switch speed too — mine's near-instant but some older units have a noticeable gap on switchover.

LochChild | 📍 Array | ⚡ Cabin/Static/Shepherds Hut builds

@TelScott75 makes a fair point — recharge is the bit that bites you.

5kWh is workable for a shortish outage if you're disciplined. On my cabin setup I've found January the real test — short days mean panels barely tickle the batteries even when it's not raining sideways.

A few things that've helped me:

• Know your actual overnight draw before disaster strikes, not a guess
• Keep a cheap Kill-A-Watt-style meter on anything you're unsure about
• The Victron app history is your friend for spotting hidden loads

Honestly 5kWh is tight for 18 hours in winter unless your heating's sorted independently. @HeatherGazer's right that heating will drain you fast. Gas/diesel backup for warmth changes the calculation completely.

RogerHobbs | 📍 Worcestershire | ⚡ Tiny House / Off-Grid

@CrispyRoamer 5.12kWh is workable but it depends entirely on your load discipline. The Victron MultiPlus-II is a solid choice — have you set up the ESS assistant with a minimum SOC threshold? Worth configuring it to cut non-essentials automatically at say 20% rather than relying on yourself to remember at 2am during a storm.

Also worth looking at your standby loads — fridges, phone chargers, always-on inverter draw all quietly nibble away. Run a proper audit with a clamp meter and you might find an extra 300-400Wh hiding there.

18 hours is genuinely achievable if you're sensible, but I'd sleep easier with a small generator as a backstop rather than purely relying on solar for recharge during a January outage. Even a cheap EU2200i would cover you.

Taffy29 | 📍 Array | ⚡ Off-Grid Living

One figure nobody's put on the table yet — your MultiPlus-II 3000 has a standby draw of roughly 20-25W continuously. Over 18 hours that's 360-450Wh just keeping the inverter alive before you've boiled a kettle. On a 5.12kWh pack with a sensible 80% DoD ceiling (4.1kWh usable), that standby overhead is meaningful.

I'd strongly suggest enabling the Dynamic cutoff and AES (Automatic Economy Switching) in VictronConnect — cuts standby consumption noticeably on lighter loads. Made a measurable difference on my own Fogstar setup during a 22-hour outage last winter.