Campervan 12V to 230V Inverter Calculator
Calculate continuous wattage and surge power to choose the right pure sine wave inverter (500W to 3000W).
🔌 Your 230V Appliances
Create your simultaneous usage scenario. Only add the 230V mains appliances you plan to run at the exact same time through your inverter (e.g. charging a laptop while running a blender).
12V to 230V Inverters in a Campervan: Why Bigger Isn't Always Better
To run standard UK 3-pin household appliances in your campervan, you need to install a 12V to 230V inverter. This essential piece of kit converts the 12V DC power stored in your leisure battery into 230V AC mains electricity.
It is tempting to buy the biggest model possible, such as a 3000W inverter, thinking that "more is better". In vanlife, this is a serious electrical mistake! An inverter consumes energy simply by being switched on. This is known as "standby draw" or "phantom consumption". A 300W model may draw as little as 0.3A idling, whereas a 3000W model can draw up to 3A continuously. Leave it switched on overnight by accident, and your large lithium battery could lose over 70Ah for no reason. Our inverter sizing calculator helps you find the sweet spot for your actual daily power needs.
The "Start-Up Surge" Trap
Some 230V appliances contain electric motors or compressors—such as blenders, power tools, hair dryers, fridges, and water pumps. The exact moment you switch them on, the motor requires a massive burst of energy to get spinning. It can draw up to 2 to 3 times its rated power for a fraction of a second. This is known as peak load or surge power.
If you plug a 500W blender into a 500W inverter, the inverter will likely trip into overload protection and cut the power immediately because the start-up surge spikes to 1000W. Our calculator automatically accounts for this extra demand whenever you check the "Motor / Surge" box.
Pure Sine Wave vs Modified Sine Wave
If there is one golden rule for campervan electrics, it is this: avoid "Modified Sine Wave" inverters. While they are available online at enticingly cheap prices, they produce a harsh, choppy electrical signal. This can cause motors to hum, reduce the lifespan of appliances, and even ruin sensitive electronics like laptop chargers, electric toothbrushes, or e-bike chargers. Always choose a Pure Sine Wave inverter, which delivers power just as smooth and clean as a domestic UK wall socket.
B2B charger, MPPT solar controller, or 230V mains hook-up... Learn how to combine your charging sources smartly in our complete campervan electrical guide.
Frequently Asked Questions
What is a Pure Sine Wave inverter?
A Pure Sine Wave inverter recreates a smooth, clean AC electrical waveform identical to standard UK domestic mains electricity. This guarantees the safe operation of sensitive electronic devices (laptops, TVs, e-bike battery chargers, CPAP machines). Cheap "Modified Sine Wave" alternatives produce a jagged signal that can hum, overheat, or permanently damage your chargers.
Why does my inverter beep or trip when I turn on an appliance?
This is almost always caused by a peak power (surge) issue. Appliances with motors or compressors (blenders, drills, small fridges) often require 2 to 3 times their rated continuous power for a second or two as they start up. If this surge exceeds the inverter's maximum peak load rating, its internal protection will instantly trip to prevent overheating.
Can I leave my inverter switched on all the time?
No, this is strongly discouraged! Inverters draw a constant "standby current" (or phantom draw) simply to power their cooling fans and internal electronics, even when nothing is plugged in. A large 2000W inverter left on 24/7 can drain up to 30Ah–50Ah from your leisure battery over a weekend for no reason. Always switch it off when not actively using 230V mains power.
Can I run an induction hob off a 12V leisure battery inverter?
Yes, but it requires a serious system setup! A single-zone induction hob typically draws 1800W to 2000W. At 12V, this pulls nearly 170 to 200 Amps through your cables. You will need a Pure Sine Wave inverter rated at least 2000W (continuous), heavy-duty battery cables (typically 35mm² or 50mm²), and a high-discharge Lithium (LiFePO4) battery bank capable of delivering that level of current without voltage collapse.
Where is the best place to mount an inverter in a campervan?
As close to your leisure battery bank as possible! The 12V cable between the battery and the inverter carries extremely high current, so it must be kept as short as possible (ideally under 1 metre) to prevent voltage drop and excessive heat. Conversely, the 230V AC cable running from the inverter to your 3-pin sockets carries much lower current and can easily run several metres across the van without loss.
Does the inverter need to be bonded to the vehicle chassis?
Yes, for electrical safety and compliance with UK campervan wiring standards (BS 7671 Section 721). Quality inverters feature a dedicated earth/ground terminal on their metal chassis. This should be connected directly to the vehicle's metal chassis using a suitable earth cable (typically 6mm² or 10mm² tri-rated cable).
Do I need a 230V inverter to charge my mobile phone?
No! Stepping 12V DC battery power up to 230V AC mains, only for your phone's wall plug to convert it back down to 5V DC, wastes roughly 15-20% of the energy in heat losses alone. It is far more efficient to wire native 12V USB and USB-C (PD) sockets directly into your 12V fuse box.
Can I plug an extension lead into a 500W inverter?
Yes, the physical number of sockets doesn't matter. What matters is total power draw: the combined wattage (W) of all 3-pin appliances plugged into that extension lead and running simultaneously must not exceed your inverter's continuous rating (500W).
Which inverter brands are recommended for UK van builds?
In the UK van conversion community, Victron Energy (specifically their Phoenix and MultiPlus series) is widely regarded as the gold standard for build quality, efficiency, and reliability. Other reputable brands offering excellent Pure Sine Wave models include Renogy, Sterling Power, Ective, and Giandel.
Do I need a fuse between the leisure battery and the inverter?
Yes, an inline fuse is non-negotiable! This is the highest-current cable in your entire van build. You must fit a heavy-duty fuse (such as a Mega Fuse or ANL fuse) as close as possible to the positive battery terminal (within 30cm). Size the fuse based on your cable's current rating and inverter peak draw—never fit an inverter without fuse protection on the positive supply line.
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