A self-built power station is not automatically cheaper. At around 1kWh it costs more than a Jackery and weighs three times as much. Above about 2kWh the arithmetic flips hard, and by 3.5kWh you are paying roughly a third of what a finished unit costs per watt-hour. This guide gives you the crossover, the parts that are genuinely in stock in the UK, and the wiring that keeps it safe.
Most build-your-own guides skip that first paragraph, because the honest version costs them the sale. It is worth being straight about it, because building the wrong size is the most expensive mistake in this whole exercise.
Build or buy, decided by size
Everything turns on capacity. A ready-made power station bundles the battery, inverter, charge controller, casing and fast charging into one warrantied box, and at small sizes that bundle is genuinely good value. What you cannot do is make it bigger, and that is where it loses.
| Capacity | Self-build | Ready-made | Per watt-hour | Verdict |
|---|---|---|---|---|
| ~1kWh | ~£470 for 1,280Wh | £419 for 1,070Wh | 37p vs 39p | Buy one |
| ~2kWh | ~£560 for 2,560Wh | £699 for 1,432Wh | 22p vs 49p | Line ball |
| ~3.5kWh | ~£686 for 3,584Wh | No direct equivalent | 19p vs 49p | Build it |
At 1kWh the self-build is nominally a couple of pence cheaper per watt-hour, and that margin disappears the moment you count your own afternoon, the lack of a single warranty, and the fact that the finished unit weighs about 11kg while yours weighs closer to 20kg with the case. Below 1kWh, buy one. There is no shame in it and this page will still point you at a good one.
Above 2kWh nothing off the shelf competes, because manufacturers price large capacity as a premium feature. A 280Ah battery is 3,584Wh for £343. The nearest finished product to that is under half the size for twice the money.
If you can carry it to where you need it, buy a finished unit. If it is going to live in a boat, a shed, a horsebox or the back of a car and mostly stay there, build it.
What "building your own" should actually mean
There are two very different things people mean by this, and only one of them belongs in a guide like this.
The version worth doing is assembly from finished modules. You buy a drop-in 12V lithium iron phosphate battery that already contains its own battery management system, an inverter, a solar charge controller, a fuse and some cable, and you connect them together. It is careful work but it is not electrically adventurous.
The version this guide deliberately avoids is building the battery itself from bare cells. That means top-balancing individual cells, fitting a separate management board, and torquing busbars to a spec. People do it and some do it well, but the failure mode is a lithium fire, which is self-sustaining, produces its own oxygen and cannot be put out with a normal extinguisher. A drop-in battery with the management built in costs perhaps twenty pounds more and removes that entire category of risk.
A built-in BMS with a stated continuous current, and low-temperature charge protection. The second matters more in Britain than most guides admit - charging lithium iron phosphate below freezing damages it permanently, and an unheated shed in January is below freezing. A battery with low-temp cutoff simply refuses the charge instead.
The five parts you need
A power station is five things in a box. Everything else is convenience.
- The battery. A 12V LiFePO4 unit with an integrated BMS. This is most of your cost and all of your capacity.
- The inverter. Turns 12V DC into 230V AC at a UK socket. It must be pure sine wave - modified sine upsets laptop chargers, anything with a motor, and some medical equipment.
- The solar charge controller. An MPPT unit, not the cheaper PWM sort. MPPT recovers noticeably more from a panel in the weak, diffuse light Britain specialises in.
- Protection. A fuse at the battery, correctly sized cable, and a busbar if you are connecting more than one thing.
- A box. Something that stops it all sliding about and keeps the weather off.
You will also want a panel, which is a subject of its own - the portable panels guide covers what is worth buying and what folds up small enough to be useful.
Working out the size you need
Add up what you actually run, in watts, and multiply by the hours. That number in watt-hours is your daily draw, and your battery wants to be roughly twice it so you are not flattening it every day.
| What you run | Draw | Over a day | From a 100Ah battery |
|---|---|---|---|
| Bite alarms and a bivvy light | ~6W | ~70Wh | Two weeks |
| Phone and power bank charging | ~15W | ~60Wh | Weeks |
| Laptop and a router | ~75W | ~600Wh | Nearly two days |
| 12V compressor fridge | ~45W avg | ~480Wh | Just over two days |
| Kettle, per boil | ~700W | ~40Wh a boil | Around 25 boils |
| Fan heater | ~1,500W | Not viable | 45 minutes |
A 12V 100Ah battery holds 1,280Wh on paper. Take off the inverter's conversion losses and roughly 1,100Wh reaches your appliances. The kettle looks alarming as a wattage but is fine as a total, because you only run it for three minutes. Heating is the opposite and is simply not a battery job, which is the same conclusion the garden office guide reaches from the other direction.
A 1000W inverter burns 10 to 20W simply being switched on, whether anything is plugged into it or not. Leave it on for a weekend and it quietly eats 700Wh - more than half a 100Ah battery, for nothing. Switch it off between uses, and run anything that can take 12V directly from 12V.
Wiring it without setting fire to it
The electrical risk in this build is not the 230V side. It is the 12V side, where a 1000W inverter pulls about 83 amps and a short circuit across a lithium battery can deliver several hundred amps into whatever is nearest.
Fuse at the battery, not at the appliance. A 150A ANL fuse on the positive lead, within about 300mm of the terminal. The fuse exists to protect the cable, so it belongs at the end where the energy comes from.
Size the cable properly. 25mm² - sold as 4AWG - for a 1000W inverter over a run under two metres. Undersized cable does not trip anything, it just gets hot, and heat inside a sealed box is exactly what you do not want.
Order of assembly. Mount everything first, then wire, then connect the battery last. Negative on last and off first. Expect a spark when you connect the inverter, because its capacitors charge instantly - that is normal, and a reason not to have the fuse in place while you fiddle.
On the 230V side, use an RCD, and never connect the inverter output to your house wiring. Part P of the Building Regulations does not apply here because a portable box is not a building, but the Electricity at Work Regulations still expect the work to be done competently.
The real numbers
Both builds below use parts confirmed in stock on Amazon UK at the time of writing. Prices move, so treat them as the shape of the answer rather than a quote.
| Part | 1.3kWh build | 3.5kWh build |
|---|---|---|
| LiFePO4 battery | 100Ah - £153 | 280Ah - £343 |
| Pure sine inverter | 1000W - £110 | 1000W - £110 |
| MPPT controller | 20A - £83 | 20A - £83 |
| Case | £39 | £65 |
| Fuse, busbar, cable, terminals | £85 | £85 |
| Total | ~£470 | ~£686 |
| Per watt-hour | 37p | 19p |
Note what changes between the two columns and what does not. The inverter, controller and wiring cost the same either way. Only the battery scales - which is precisely why building small is poor value and building large is excellent value. You are amortising a fixed £278 of supporting parts across whatever capacity you choose.
Recommended parts
Every item below was checked as in stock on Amazon UK when this page was written.
ECO-WORTHY 12V 280Ah LiFePO4
Three and a half kilowatt-hours for the price of a mid-range finished unit holding well under half that. Bluetooth monitoring and low-temperature charge protection are both included, and the 200A management system leaves plenty of headroom for a 1000W inverter. It weighs a little over 30kg, so this is a build that lives somewhere rather than one you carry.
amazon Check Price on Amazon →DCHOUSE 12V 100Ah LiFePO4
The sensible entry point if you want to build rather than buy but are not ready to spend on 280Ah. Well reviewed, in stock, and includes the Bluetooth monitoring and low-temperature cutoff that matter in a British winter. Be honest with yourself first though - at this capacity a finished power station is a reasonable alternative.
amazon Check Price on Amazon →Renogy 1000W Pure Sine Wave Inverter
Pure sine output, proper UK three-pin sockets and a wired remote so you can switch it off without opening the box - which, given the idle draw, you will want to do often. The 2000W surge rating covers the moment a fridge compressor or a pump kicks in. A 600W unit is around £89 if you are never running anything heavy.
amazon Check Price on Amazon →Renogy Rover 20A MPPT
MPPT rather than PWM, which is worth the difference in British light, and the Bluetooth is built into the unit rather than sold separately as a dongle. Twenty amps covers a couple of 100W panels comfortably. Size up to 40A only if you are planning more than about 260W of panel.
amazon Check Price on Amazon →Jackery Explorer 1000 v2
The honest recommendation for anyone who worked through the numbers above and landed under 1kWh. It costs less than the equivalent self-build, weighs half as much, arrives working, and carries a single warranty rather than five. Buying this instead of building is not a failure of nerve, it is the right answer at this size.
amazon Check Price on Amazon →Where it beats a generator outright
This is the argument that convinces most people, and it has nothing to do with money.
UK campsites and fisheries very commonly ban petrol and diesel generators. Not restrict - ban, on noise grounds, and enforced. What they permit almost universally is battery power. One fishery rule sheet puts it in five words: no generators, power banks only.
A self-built LiFePO4 station is silent, produces nothing to breathe, needs no fuel carried in a car boot, and recharges from a panel while you sleep. For long fishing sessions, a narrowboat on a rural mooring or a beach hut with no supply at all, it is not a compromise on a generator. It is the only thing you are actually allowed to run.
Rules are set venue by venue rather than nationally, so check yours before you travel. The pattern is consistent enough to plan around.
Summary
- Under 1kWh, buy a finished unit. A self-build costs more, weighs more and carries no single warranty
- Over 2kWh, build it. Roughly 19p per watt-hour against about 49p, and the gap widens with size
- Use a drop-in battery with a built-in BMS, never bare cells
- Insist on low-temperature charge protection - a British shed goes below freezing
- 150A ANL fuse within 300mm of the battery, and 25mm² cable for a 1000W inverter
- Pure sine wave inverter only, and switch it off between uses - idle draw is 10-20W
- Silent operation means it is permitted where generators are banned, which is most fisheries and campsites
The short version: the parts that are not the battery cost about £278 no matter what size you build. Spread that across 1,280Wh and it hurts. Spread it across 3,584Wh and the whole thing becomes the cheapest stored electricity you can buy.
Frequently Asked Questions
Is it cheaper to build your own power station?
Only above a certain size. At around 1kWh a self-build comes to roughly £470 in parts against £419 for a Jackery Explorer 1000 v2 that is lighter, warrantied and needs no assembly. At around 3.5kWh a self-build costs about £686, which works out at 19p per watt-hour against roughly 49p for the nearest ready-made unit. The crossover sits at about 2kWh.
Can I build a power station from bare lithium cells?
You can, but this guide deliberately does not cover it. Assembling raw cells means balancing them, fitting a separate battery management system and torquing busbars correctly, and getting any of it wrong risks a fire that is extremely difficult to put out. A drop-in 12V LiFePO4 battery has the management system built in, costs little more, and removes the entire category of risk.
What size fuse do I need for a 1000W inverter?
On a 12V system a 1000W inverter draws roughly 83A continuously, so a 150A ANL fuse is the standard choice. Fit it on the positive cable within about 300mm of the battery terminal. The fuse protects the cable rather than the inverter, which is why it goes at the battery end.
Can I take a DIY power station to a campsite or a fishery?
Usually yes, and this is one of the strongest reasons to build one. Most UK campsites and fisheries ban petrol and diesel generators on noise grounds while explicitly permitting battery power - one fishery rule sheet reads simply, no generators, power banks only. Rules are set venue by venue though, so check before you travel.
How long will a 100Ah battery run a laptop?
A 12V 100Ah LiFePO4 battery holds 1,280Wh, of which roughly 1,100Wh reaches your appliances once inverter losses are taken off. A 60W laptop therefore runs for about eighteen hours. The bigger drain is usually the inverter itself, which burns 10 to 20W just being switched on.
Do I need an electrician to build one?
No. Part P of the Building Regulations applies to fixed wiring in buildings, and a portable box is not a building. You are still covered by the Electricity at Work Regulations, which means the work has to be done competently - correct cable sizing, proper fusing and an RCD on the 230V side. Never wire an inverter output into your house circuits.
Can I charge it from the mains as well as from solar?
Yes, and most people do. A separate LiFePO4 mains charger tops the battery up before a trip, while the solar controller keeps it going once you are out. Use a charger rated for lithium iron phosphate specifically, because a lead-acid charger uses the wrong voltage profile and will either undercharge the battery or stress it.