Do I Need an Inverter? A Practical Guide for Motorhomes & Campervans

If you’re thinking of upgrading your Motorhome or campervan electrics, the inverter is usually the first thing people ask about — and it’s also one of the easiest bits of kit to overspend on.

This guide breaks down what an inverter does, when you actually need one, and how to choose the right size, helping you feel more confident in your decisions, especially when selecting between inverter types and accessories.

What an inverter actually does

An inverter converts your 12V (or 24V) battery power (DC) into 230V mains power (AC) — the same type of power you get from a household socket in the UK.

In plain English, it lets you run “plug-in” appliances when you’re not on hook-up.

Reasons you might want an inverter

You probably want an inverter if you want to use any of the following off-grid:

·        Laptop chargers, camera chargers, drone batteries

·        TV, games console, Starlink, Wi‑Fi routers

·        Coffee machines, air fryers, microwaves (high power)

·        Hair dryers, straighteners (very high power)

·        Power tools, battery chargers

·        Medical equipment that requires 230V

It can also make your van feel more “home-like, especially if you’re doing longer trips or wild camping.

Reasons you might NOT need an inverter

An inverter isn’t always essential. You might not need one if:

·        You mainly stay on campsites with electric hook-up

·        Your needs are mostly 12V or USB (lights, water pump, phone charging)

·        You’re happy using a gas hob for cooking and a 12V fridge

·        You only want to charge small devices (USB-C PD can cover a lot now)

A common mistake is installing a large inverter “just in case,” only to discover the battery bank can’t realistically support the loads you want to run.

Pure sine wave vs modified sine wave

For vans and motorhomes, a pure sine-wave power supply is the safe choice.

Pure sine wave inverters:

·        Run sensitive electronics properly

·        Reduce buzzing/overheating in chargers and motors

·        Play nicer with induction hobs, microwaves, and some battery chargers

Modified sine-wave units can be cheaper, but they can cause issues with modern electronics and certain appliances. If you’re investing in a decent electrical system, it’s rarely worth cutting corners here.

What size inverter do I need?

Inverter sizing comes down to two things:

1.       Continuous power (what it can supply all the time)

2.       Surge power (the short “startup” spike for motors/compressors)

Step 1: List what you want to run

Write down the appliances you want to use off-grid and their wattage. If the label shows amps instead, you can estimate watts using these simple calculations.

In the UK, mains voltage is roughly 230V.

Step 2: Decide what will run at the same time

If you’ll run a laptop (100W) and a TV (80W) together, that’s ~180W.

If you want a coffee machine (1,200–1,500W) or microwave (1,000–1,500W), that changes everything.

Step 3: Add headroom

As a rule of thumb, choose an inverter with 20–30% headroom above your expected maximum continuous load.

Typical inverter sizes (rough guide)

·        300–500W: laptops, camera charging, small TV

·        800–1,000W: light mains use, some kitchen appliances (not all)

·        1,600–2,000W: microwaves, coffee machines, hair tools (battery bank must match)

·        3,000W+: weighty off-grid “house-like” loads (often best suited to 24V systems and big battery capacity)

OK, so a Victron Multiplus 3000 means it's a 3000W inverter, right?

Wrong. Victron often rate inverters in kVA (apparent power), not watts (real usable power). They’re related, but they’re not the same thing. Watts (W) = the useful power your appliances actually consume. kVA = the inverter’s total “electrical capacity” including losses and reactive loads (motors, compressors, some chargers). A good rule of thumb is kW ≈ kVA × 0.8 Pf (power factor) kW≈kVA×0.8

Example:

A 3,000 VA (3.0 kVA) inverter typically provides about 2,400 W of continuous usable power for most real-world loads.

Why it matters:

Some appliances (anything with a motor or compressor, like fridges, air conditioners, and power tools) may require extra “surge” power to start, so we size the inverter to handle both running watts and start-up surge—not just the headline kVA rating.

Can I run pretty much anything at 230V from my 12V Leisure Batteries, then?

There are limits, let's go through why with a quick estimate:

Example: a 1,500W appliance on a 12V system (assuming ~90% efficiency):

1500/13.6 x 0.9 = 139A, think about that for a second!

That’s a lot of amps, because of the low voltage, which means a lot of heat, which means waste! This is why inverter, battery choice and cable size go hand in hand.

12V vs 24V systems, a simple way to think about it

Most campervans and motorhomes are built around 12V, which is suitable for most setups. But as inverter size (and power demand) goes up, 24V can make life easier because it reduces current for the same power.

Here’s the key idea:

·        Same watts, higher voltage = lower amps

·        Lower amps = thinner cables (sometimes), less voltage drop, and generally a happier install

A rough comparison for a 1,500W load:

·        12V: ~139A (as above)

·        24V: roughly half the current

If you’re planning a larger inverter (often 2,000 W+) orwant to run heavier loads more often, it’s worth considering a 24V battery bank and inverter from the start.

Why LiFePO4 batteries are better

LiFePO4 (Lithium Iron Phosphate) batteries are an excellent match for inverter systems because they typically:

·        Deliver high current without voltage sag (appliances run better)

·        Offer far more usable capacity (you can use more of the battery safely)

·        Recharge faster (great with solar and DC-DC charging)

·        Last longer in cycle life than traditional lead-acid options

·        Weigh less for the same usable energy

Lead-acid batteries can work, but with bigger inverters, they often struggle: voltage drops, performance issues, and reduced usable capacity under high loads.

Other accessories you’ll likely need (for a safe, tidy install)

An inverter is only one part of the system. Depending on your setup, you may also need:

·        Correct cabling (thick enough for the current and cable length)

·        Proper fusing close to the battery (critical for safety)

·        Battery isolator / disconnect for maintenance and emergencies

·        Busbars for clean, reliable connections

·        Battery monitor / shunt so you can see the real state of charge

·        Solar + MPPT controller to keep batteries topped up off-grid

·        DC-DC charger for reliable charging from the vehicle alternator

·        RCD/MCB consumer unit on the AC side (especially for multiple sockets)

·        Earthing/bonding done correctly for your vehicle and inverter type

·        Ventilation and mounting (secure, protected, and serviceable)

If you’re adding multiple 230V sockets, consider how you want the van to be used day—to—day. Tidy cable runs and sensible socket placement make a significant difference.

Common mistakes to avoid

·        Buying an inverter based on “maximum watts” without checking battery capacity

·        Oversizing the inverter “just in case” (cost, cabling, and safety requirements jump quickly)

·        Using undersized cables or incorrect fusing

·        Ignoring surge loads (compressors, pumps, some microwaves)

·        Assuming solar alone will run high-wattage appliances indefinitely

Quick rule-of-thumb recommendations

If you want a simple starting point:

·        Mostly charging devices + occasional TV: 300–500W pure sine

·        General off-grid comfort, light kitchen use: 1,000W pure sine

·        Coffee machine / microwave / hair tools: 1,600–2,000W pure sine + serious battery/charging setup

Want help choosing the correct setup?

If you tell us which appliances you want to run (and whether you’re 12V or 24V), we can recommend an inverter size and a battery/charging setup that match — so it’s safe, tidy, and actually works off-grid.

Book a call