Home backup power — where to start?

Spot on what everyone's saying about the van being your testing ground. I spent years thinking I'd need a massive system before I actually lived with the constraints — turned out I was way off on what I'd actually use day-to-day.

What I'd add: document everything while you're in the van. Your actual consumption patterns, seasonal variations, how you actually behave when power's tight (you'll be shocked). I kept a spreadsheet of usage across different seasons and it completely changed what I spec'd for the tiny house.

The other thing — and this matters for your future build — is that van kit doesn't necessarily translate 1:1. The Victron setup that works brilliantly at 100Ah in a compact space might need rethinking at 400Ah in a static setup. But the principles stick with you. You'll understand what oversizing actually means instead of just guessing.

One practical tip: if you're serious about the transition, size your van batteries and solar for what you think the tiny house needs, not what fits the van. Better to have surplus capacity now than realise in two years you've learnt everything

The van's your cheapest education, but don't cheap out on it—get proper Victron monitoring sorted now so you actually know what you're using rather than guessing. Too many people go full Renogy and end up with a garage full of dead lithium because they couldn't be bothered with a BMV-712.

For the tiny house migration, your real learning curve isn't the hardware, it's realising winter consumption is three times summer and you'll absolutely need more battery than you think you can afford. The van teaches you that quickly enough if you're paying attention.

One thing nobody mentions: the van's got space constraints that force good discipline. Your tiny house won't, and that's where systems get bloated. Stick to what actually works in the van, scale it up proportionally, and you'll be golden.

What's your current consumption looking like, and are you planning mains backup for the tiny house or going full island mode?

You lot are absolutely right about the van being your classroom. I've been living on a narrowboat for three years now, and honestly, it's the same principle—confined space, real constraints, nowhere to hide from your mistakes.

What I'd add: document everything from day one. I didn't, and I spent months puzzled about why my battery was dropping faster than expected before realising I had phantom loads I'd completely overlooked. Now I know exactly which appliances are the culprits.

For your tiny house transition, the advantage of starting in the van is you'll know your actual consumption patterns, not some theoretical figure. That'll save you thousands when you spec the permanent system. I went from thinking I'd need a massive battery bank to realising I could get away with far less because I'd genuinely cut the waste.

One practical thing: get a basic energy monitor installed now (even something like a Shelly EM is cheap as chips). When you move to the house, you'll have proper baseline data rather than guessing. Makes spec'ing your Victron setup infinitely easier.

The van's your sandbox. Use it properly and your tiny house build will

Your van's basically a £500 mistake waiting to happen if you skip the monitoring side — @RetiredChef's spot on there. I ran a bodged setup for two years before biting the bullet on a proper Victron GX and it was like switching from reading tea leaves to actual data.

Real talk though: test your consumption first before buying anything. Most people overestimate by about 40% because they forget how much a kettle actually costs. Get a basic load analyser, live in the van for a month doing normal bits, then size your batteries to that reality rather than some fantasy figure.

LiFePO₄ prices have dropped enough now that they're worth the upfront cost over lead acid — better longevity for a tiny house build you'll be living in for decades. If budget's tight, hybrid approach works: smaller battery bank now, upgrade the solar and monitoring instead. You can always add another battery box later when the pennies are less tight.

What's your current consumption looking like in the van?

Spot on about the van being your testbed. I'd add — use it to work out your actual consumption patterns before you spec the tiny house system. Most people guess wildly wrong.

Since you're planning the build anyway, worth documenting everything now. What appliances you genuinely use daily, when you use them, seasonal variations. That data's gold when you're sizing batteries and solar.

One thing @RetiredChef didn't mention — get a proper energy monitor on the van (Victron BMV or even a Shelly EM for budget monitoring). Shows you exactly where power's leaking. Bet you'll find things draining overnight that you didn't realise.

For the tiny house, you'll likely want more capacity than a van can handle, but the principles stay the same. If you can live comfortably on 100Ah in the van, you'll know what 200Ah feels like for a static build. Massive difference in how you actually live with the system versus theoretically designing it.

What's your current power draw looking like in the van?

Right, @WonkyMender, here's the thing nobody mentions until you've already spent a fortune: a van's the perfect excuse to live like a medieval peasant for six months without your partner leaving you.

Seriously though, I learned more about my actual power needs in one winter on the narrowboat than I would've in five years of guessing. Turns out I

@WonkyMender — I'm in a similar boat (literally, in my case). Been running a van setup for about three years now before committing to anything permanent, and it's genuinely been invaluable.

The bit I'd emphasise that others haven't quite nailed: use your van to trial different battery chemistry and monitoring setups. I started with cheap lithium, hated the BMS limitations, switched to LiFePO4 with a Victron BMV, and now I actually know what I need rather than guessing.

Document everything for six months minimum — your daily loads, seasonal variation, charging patterns. Sounds tedious but when you're spec'ing a proper system for the tiny house, you'll have real numbers instead of "I reckon about 10kWh a day."

One thing nobody mentions: your van's weight and space constraints will actually force you to be efficient in ways that'll serve you brilliantly in a static build. You'll naturally avoid the massive oversizing trap.

What's your current van setup like? Battery capacity, solar array size? That'll help gauge how far you can push the testbed approach

Mate, spot on about using the van as your lab. I've done exactly this and it's saved me loads.

Key thing nobody mentions — your tiny house will probably use way more than you think once you're stationary. Heating, cooking, proper fridge-freezer instead of a tiny 12v one. I jumped from a van setup thinking "job done" and had to massively upsize.

My advice: start modest, add as you go. I went Victron LiFePO4 200Ah in the van, worked brilliant for two years, then realised I needed twice that for the static caravan. At least the Victron stuff is scalable — can parallel batteries later without binning everything.

Don't overthink the solar either. Van taught me that 400W looks good on paper but doesn't cut it in winter. Better to have realistic expectations and add a backup petrol gen or grid tie-in for the house build.

What's your rough power draw looking like currently? That'll tell you whether you're "backup only" or proper off-grid territory.

@WonkyMender the van's brilliant for this. I'd focus on load profiling first — actually monitor what you're drawing daily before buying anything. Most people wildly oversize their battery banks. Get a cheap shunt monitor on your current setup, run it for a month, then you'll know what the tiny house actually needs. Saves thousands.

Spot on about the van being your testing ground — I ran mine for five years before the tiny house and it taught me everything about what I actually need versus what I think I need. Start with a cheap kill-a-watt meter, track usage for a month, then you'll know if you're after a 5kWh battery or a 50kWh one. Saved me thousands in oversizing nonsense.

Been running my setup in a static caravan for three years now. The real game-changer was sizing the battery bank after understanding my actual winter consumption — not summer optimism. What's your current power draw looking like? That'll determine whether you need LiFePO4 or lead-acid for the transition phase.

Brilliant point about using the van as a testbed. Have you thought about what loads are genuinely essential vs nice-to-haves? I'm finding that distinction absolutely crucial for my cabin setup. Once you know that, sizing becomes much clearer. Also worth noting the tiny house build gives you a chance to design the electrics properly from scratch — way ahead of retrofitting like us van dwellers.

The van's ideal for this. I'd log your actual consumption for a few weeks first—most people massively overestimate what they need. Once you've got real numbers, size your battery accordingly. Victron gear scales beautifully from van to static caravan to tiny house, so you won't be throwing money away on kit that won't transfer.