What a 400Ah Off-Grid Lithium Build Actually Costs in 2026

You've sized your system, you know you want lithium, and you're done reading "lithium vs. AGM" explainers. You just want the number. Here it is, component by component, at real retail prices as of mid-2026 — with a running total you can take to your spreadsheet.

A 400Ah bank at 12V gives you roughly 5.1kWh of usable capacity — enough to run a 12V fridge, lights, water pump, fans, laptops, and a modest induction or coffee habit for a day or two without sun. It's the sweet spot for a serious van, a full-time skoolie, or an off-grid cabin that isn't trying to run air conditioning off batteries. This breakdown assumes a 12V system, a 2,000–3,000W inverter/charger, around 400–600W of solar, and that you're doing the install yourself.

Prices below are current public retail figures from Amazon, manufacturer sites, and major solar retailers. Your exact total will shift with sales and which brands you pick, but this is an honest middle-of-the-road build using gear people actually trust.

The batteries

This is the line item that dominates the budget, so it's worth getting right. Four 100Ah LiFePO4 batteries wired in parallel is the most common way to hit 400Ah at 12V. Using Battle Born 100Ah batteries — a default for builders who want a proven name and a 10-year warranty — the standard 100Ah model runs about $874 each at retail.

The spread here is real: a name like Battle Born or Dragonfly Energy costs roughly double a value brand. There's a defensible argument for both. The premium names buy you better cold-weather behavior (built-in heating on the heated variants), tighter BMS firmware, and warranty support you'll actually be able to reach. For the running total below, we'll assume a mid-tier build — blending a high-capacity Epoch or Dakota Lithium unit with careful shopping — and carry $2,400 for the bank. Go all–Battle Born and this line roughly doubles; go value-brand and it drops by a third. That single choice is the biggest swing in the whole build.

The inverter/charger

For a build this size, a combined inverter/charger earns its place — one box that turns DC into 120V AC and also charges the bank from shore power or a generator. A Victron MultiPlus-II 12/3000 is the common pick and currently runs around $1,100–1,200 at retail. If you only need 2,000W and a 30A shore connection, you can drop to a smaller unit and save a couple hundred dollars. A standalone 2,000W pure sine inverter (Renogy, for example) plus a separate converter is cheaper still but means more wiring and more failure points.

Running total so far

Solar charging

A 400–600W array keeps a 400Ah bank topped up in most conditions. Using Renogy 200W rigid monocrystalline panels at roughly $150 each, a 400W array (two panels) lands near $300; 600W (three panels) near $460. We'll carry $400.

That array needs an MPPT charge controller. A Victron SmartSolar MPPT 100/50 handles up to ~700W on 12V and runs about $190–230. For bigger arrays, step up to a 150/100. MidNite Solar and EG4 make solid controllers in the same range if you're building around their ecosystems. Carry $210.

Battery monitoring

Skipping a proper shunt-based monitor is the most common regret in DIY builds — a voltage reading alone won't tell you true state of charge on lithium. A Victron SmartShunt 500A runs about $130 and talks to your phone over Bluetooth. Non-negotiable on a bank this size. Carry $130.

DC-DC charging (vehicle builds)

If this is a van or RV with an alternator, a DC-DC charger lets you charge the house bank while driving without cooking your alternator. A Victron Orion-Tr Smart 12/12-30A is about $244. Cabin builds can skip this line entirely. We'll include it: carry $244.

The wiring, fusing, and the stuff nobody photographs

This is where budgets quietly blow up. Doing it right means proper-gauge cable, lugs, a Class-T or ANL main fuse, MRBF terminal fuses on the batteries, a busbar or distribution block, a battery switch, breakers for the solar and inverter circuits, and a bag of heat shrink and ferrules. Bought as quality individual parts, plan on $350–500. We'll carry $400.

The full build, at retail

Figures are public retail prices as of June 2026 and will move with sales and brand choice. A premium all–Battle Born / all-Victron version of this build runs closer to $6,500; a value-brand version can dip under $3,500.

So: call it roughly $4,900 at retail for a middle-of-the-road 400Ah build, with the realistic range running from about $3,500 to $6,500 depending on how hard you lean into premium batteries and electronics. Most of that swing lives in the battery bank.

None of these numbers include the things that don't show up on a parts list: the panel mounts, the roof penetrations, the time you'll spend crimping lugs, and the one part you'll inevitably order twice. Budget a little headroom.