Avis sur installation auto conso 3kW avec batterie

Been thinking about this lately as I'm planning a similar-sized setup — roughly 3kW of panels with battery storage, partly for the boat but also as a home emergency backup.

A few things I'm still unsure about:

Inverter sizing — does anyone run a Victron Multiplus-II at a lower VA rating than their panel capacity, or is that asking for trouble when everything kicks in at once? I've seen conflicting advice on this.

Battery chemistry — I'm leaning toward Fogstar Drift LiFePO4 cells for the cost savings, but wondering whether the BMS comms with a Cerbo GX is worth the extra faff vs just letting the Victron manage it via voltage alone.

DNO notification — for a UK install at this scale, even off-grid, does anyone know if there's a point where you have to notify your DNO regardless? I know G98/G99 applies to grid-tied export, but what about purely self-consumption with no feed-in at all?

The French self-consumption regulations seem a fair bit clearer than what we've got here, honestly. Over there they have a defined process (their Consuel sign-off equivalent). Here it feels like you're piecing it together from various MCS docs and forum posts.

Anyone gone through a similar 3kW self-consumption build in the UK? Particularly interested if you've got a hybrid setup that can also act as emergency backup — that's the main goal for me rather than grid export.

@Taffy — French thread title on a UK forum, that's a new one. Anyway, 3kW with battery backup is perfectly sensible but you've not actually finished your question, which makes this difficult to answer properly.

What I will say from my static caravan setup: don't underestimate your inverter sizing. People obsess over panel wattage and completely ignore what's actually drawing power. My Victron Multiplus has saved me grief repeatedly because it handles surge loads properly — cheap inverters absolutely do not.

Also "home emergency backup" and "boat" are completely different use cases electrically. Marine installations have specific regs (BS EN ISO 13297) that land-based setups don't. Don't just transplant one approach onto the other.

Finish your question and we might get somewhere useful.

@Taffy the boat/home dual-use angle is something I've done myself — my narrowboat setup feeds a Victron MultiPlus-II which can island from the grid when needed. Key thing people miss with "emergency backup" is defining what loads you actually need to cover. A 3kW array with say 10kWh of Fogstar Drift LiFePO4 will carry lighting, fridge and phone charging indefinitely in summer but you'll feel it in January.

Worth sizing the inverter for your peak loads rather than average — kettles and small appliances bite hard. The MultiPlus-II 3000 handles most domestic spikes without drama.

Also if this is going on a boat and acting as home backup, check your DNO rules around grid-tied vs off-grid configuration. They're two very different regulatory worlds.

@PennineNomad jealous of that MultiPlus-II setup — mine's just a Fogstar Drift 100Ah pretending it's a proper off-grid system while I live in a shed.

@SolarKeith don't knock the Fogstar Drift, I've got two of them in my static and they've been solid for 18 months — touch wood.

@Taffy the dual-use thing sounds clever until you're trying to lug gear between a boat and a house every time there's a power cut. Ask me how I know. Ended up just keeping separate setups in the end, cost more but far less faff.

3kW panels is decent but what's your battery capacity? That's where most people underspec and then wonder why they're running low by 9pm in November. UK winters are brutal for solar — I run 400Ah and still get caught out.

What inverter are you looking at?

Touching on the dual-use angle @Taffy mentioned — worth thinking carefully about your inverter sizing if you genuinely want home emergency backup capability. A 3kW panel array is great, but your inverter needs to handle surge loads from things like a fridge compressor or a sump pump kicking in, which can spike to 3-4x their rated draw momentarily.

Also, if the boat is moored away from home regularly, consider whether you want the battery bank split across both locations or fully portable. Victron's ecosystem handles that flexibility well, but it does add cost.

@ZFS_OffGrid makes a fair point about the Fogstar Drift — decent value per kWh for static applications. For something moving between locations though, I'd want cells with a bit more vibration tolerance rated into the spec sheet.