LPG Conversion Guide: When Gas Beats Petrol

Petrol generators are everywhere. They’re convenient, portable, and you can fill them at any garage. So why would anyone bother converting to LPG?

Because petrol goes stale. LPG doesn’t.

I’ve lost count of clients who stored a petrol generator for “emergencies” only to find it won’t start when the power actually cuts. Gummed carburettor. Varnished fuel. Dead battery from trying to start it.

LPG sits in a tank for years without degrading. When you need backup power, it fires up. That reliability alone makes conversion worth considering.

But there’s more to it than that. Let’s break down when gas actually beats petrol—and when it doesn’t.

The Real Benefits of LPG Conversion

Fuel Storage and Stability

Petrol has a shelf life of 3-6 months before it starts breaking down. Add stabiliser and you might stretch that to 12 months. After that, you’re risking carburettor damage.

LPG? Stable indefinitely. A full LPG tank will work perfectly whether you filled it yesterday or five years ago.

For standby generators that sit idle most of the time, this changes everything. No more draining fuel systems before storage. No more stale fuel problems. Just reliable starting when needed.

Running Costs

LPG is cheaper than petrol. Not massively, but enough to matter over hundreds of hours.

Current UK Fuel Costs (November 2025):

• Petrol: £1.45-£1.55/litre
• LPG: £0.70-£0.85/litre

Sounds great, right? Except LPG has lower energy density. You burn about 15-20% more volume for the same power output.

So your actual saving is around 25-35% on fuel costs. For a generator running 200 hours per year, that’s £80-150 saved annually.

Cleaner Running

LPG burns cleaner than petrol. That means:

1. Less carbon buildup in the engine
2. Longer oil change intervals
3. Spark plugs last longer
4. Valves stay cleaner

Your maintenance costs drop. Engine life extends. It’s not dramatic, but it adds up.

Emissions

If environmental impact matters to you, LPG wins easily:

• 10-15% less CO2 than petrol
• Virtually no particulates
• Lower NOx emissions
• No evaporative emissions from fuel storage

You won’t get a medal, but it’s genuinely better for air quality.

When LPG Makes Sense

Not every situation suits LPG conversion. Here’s when it’s worth doing:

1. Standby/Backup Generators

If your generator sits unused for months between runs, LPG is brilliant. No stale fuel headaches. Just reliable backup when mains power fails.

Perfect for:

• Home backup power systems
• Remote property standby units
• Business continuity generators
• Emergency power for farms

Browse our standby generator options for models that work well with LPG conversion or come LPG-ready.

2. Stationary Applications with Existing LPG Supply

Already got an LPG tank for heating or cooking? Converting your generator means one fuel for everything.

No need to store petrol separately. No trips to the garage with jerry cans. Just draw from your existing bulk supply.

Particularly relevant for:

• Rural properties on LPG heating
• Farms and agricultural buildings
• Remote holiday lets
• Off-grid homes

3. High-Hour Professional Use

Using a generator commercially for hundreds of hours per year? The fuel cost savings become significant.

Event companies, mobile catering, outdoor wedding venues—they all benefit from LPG economics over time.

Plus, cleaner running means less maintenance downtime. When the generator is making you money, reliability matters.

When to Stick with Petrol

LPG isn’t always the answer.

Portability Requirements

LPG cylinders are heavy. A 13kg propane bottle weighs 13kg empty, then you add 13kg of gas. That’s 26kg before you’ve even lifted the generator.

Compare that to 5 litres of petrol in a light plastic can. There’s no contest.

For camping, festivals, taking power to remote sites—petrol wins on portability every time. Check our leisure generator range for genuinely portable options from Honda and Yamaha.

Short Runtime Requirements

If you’re only running a generator for 30 minutes at a time occasionally, the benefits of LPG don’t really materialize.

Petrol is simpler. You don’t need regulators, gas lines, or bulk storage. Fill it, run it, done.

Cold Weather Operation

LPG struggles below about -5°C. Propane vaporizes down to around -42°C, but pressure drops as temperature falls. In really cold weather, you might struggle to get adequate gas flow.

Butane is worse—it stops vaporizing at 0°C. Stick to propane in the UK, but even that has limitations in harsh winters.

Conversion Options and Costs

You’ve got three routes to LPG operation:

Option 1: Conversion Kit

Converts an existing petrol generator to run on LPG. Usually retains petrol capability too.

Cost: £150-£400 for the kit Installation: DIY-capable if mechanically confident, or £100-200 professional fitting

Popular kits:

• Impco for larger generators
• Generic carburetor adapter kits for smaller units

Works well on generators from 2kW to 10kW. Over that, dual-fuel or purpose-built LPG generators make more sense.

Option 2: Dual-Fuel Generators

Designed from the factory to run petrol OR LPG. Flip a switch, change fuel source.

Cost: £100-200 premium over petrol-only equivalent

You get best-of-both-worlds flexibility. Use petrol for portability, switch to LPG for stationary use.

Available from most major manufacturers including Pramac and SDMO.

Option 3: Purpose-Built LPG Generators

Optimized for LPG from the ground up. Better efficiency, designed fuel systems, no compromise.

Cost: Usually 15-25% more than petrol equivalents

For permanent installations where you’ll never use petrol, this is the best engineering solution.

What You Need Beyond the Generator

Converting to LPG isn’t just swapping the fuel source. You need infrastructure.

LPG Storage Options

Portable Cylinders (5kg-47kg)

• Cheap to get started (£20-40 deposit per cylinder)
• Easy to swap when empty
• Fine for occasional use
• Annoying for frequent high-volume use

Bulk Tank (500L-1000L+)

• One-off cost: £800-2,000 to purchase (or £40-60/year rental)
• Refilled on-site by supplier
• Cost-effective for regular use
• Requires permanent location and space

For home backup, I’d go bulk tank. For mobile use, cylinders.

Gas Supply Equipment

Regulator: £30-80 Reduces cylinder pressure (7-15 bar) to generator inlet pressure (typically 30-50 mbar). Essential. Don’t skimp—cheap regulators cause inconsistent running.

Gas Hose: £20-40 Use proper LPG-rated hose with jubilee clips. Not garden hose. Not “it looks similar” hose. Proper LPG hose.

Changeover Valve (for cylinders): £40-100 Automatically switches between two cylinders when one empties. Clever bit of kit that means you never run out mid-use.

Installation Considerations

DIY vs Professional

You can DIY if:

• You’re mechanically competent
• The generator is under 5kW
• You’re using a simple carburetor adapter kit
• You’re comfortable with basic engine work

Get professional help if:

• Generator is over 5kW
• You’re installing a bulk tank
• Local regulations require Gas Safe certification
• You’re not confident (seriously, don’t bodge gas systems)

Gas Safe registration isn’t legally required for LPG bottled gas work, but it’s required for fixed tank installations and strongly recommended for everything.

Safety Requirements

LPG is heavier than air. It pools in low spots. That’s why you can’t just stick a gas generator in a basement or enclosed space.

Minimum safety setup:

• Generator at ground level or higher (not in pits)
• Adequate ventilation
• Gas detector if operating in partially enclosed spaces
• Isolation valve at the tank
• Emergency shut-off accessible and labeled

Gas leaks are serious. Get this bit right.

Performance Differences

LPG changes how your generator performs. You need to know what to expect.

Power Output

LPG typically delivers 90-95% of the rated petrol power output. A 3kW petrol generator makes about 2.7-2.85kW on LPG.

Why? Lower energy density means slightly leaner combustion and reduced cylinder filling.

If you’re running close to capacity on petrol, you’ll need to size up when converting to LPG.

Fuel Consumption

A rough guide:

Your mileage will vary (literally). These are ballpark figures for half-load operation.

Maintenance Differences

LPG changes your maintenance schedule, mostly for the better.

Less Frequent:

• Oil changes (clean combustion means less contamination)
• Spark plug replacement
• Carburetor cleaning (LPG doesn’t gum things up)

New Items:

• Regulator inspection (annually)
• Gas line leak checks (annually)
• Valve adjustment (LPG runs hotter—check valve clearances)

Overall maintenance workload drops by maybe 20-30%. Factor that into your cost comparison.

Making the Conversion Decision

Here’s a simple decision tree:

Does your generator sit unused for months at a time? → Yes: LPG makes sense for reliability

Do you already have LPG on site? → Yes: Convert, it’s a no-brainer

Do you run the generator 100+ hours per year? → Yes: Fuel savings justify conversion

Do you need portability? → Yes: Stick with petrol or dual-fuel

Is your generator over 8 years old? → Yes: Probably not worth converting—buy dual-fuel next time

The Brands That Handle LPG Well

Not all generators convert easily. Some are LPG-friendly, others are nightmares.

Easy Conversions:

• Honda (excellent aftermarket kit support)
• Yamaha (well-documented conversion procedures)
• Most Chinese clones of Honda GX engines

Available Dual-Fuel:

• Pramac
• SDMO
• Champion

Purpose-Built LPG:

• Cummins (commercial units)
• CAT (larger installations)

Browse our generator brands to compare fuel options across ranges, or check our diesel options if you’re considering multiple fuel types.

Final Thoughts

LPG isn’t automatically better than petrol. It’s better in specific circumstances:

1. Long-term storage and standby applications
2. Stationary use with existing LPG infrastructure
3. High runtime hours where fuel costs matter
4. Situations where cleaner emissions are valued

For occasional portable use, petrol remains simpler and more practical.

Convert if the benefits match your situation. Otherwise, stick with what works.