Muster vs Gas Engineer Software: Full Comparison (2026)

Gas Engineer Software has over 6,000 users. It's the default cert app for UK gas engineers — and for good reason. It was early, it focused on the trade, and the CP12 generation works.

But it was built to solve one problem: certificates. Everything else — job scheduling, invoicing, compliance, fleet tracking — either doesn't exist or feels bolted on.

Muster was built to solve the whole problem. Certificates are part of it, not all of it.

This is a direct comparison. We include pricing at every team size, a feature-by-feature breakdown, and an honest assessment of where each platform wins.

The core difference

Gas Engineer Software is a certificate and scheduling app built for gas engineers. It generates CP12s, tracks Gas Safe registrations, and handles basic job scheduling.

Muster is a full job management platform built for UK trades — including gas engineers. It generates CP12s AND handles quoting, scheduling, invoicing, GPS fleet tracking, AI, compliance, call recording, and customer payments.

Think of it this way: Gas Engineer Software replaces your paper certificate pad. Muster replaces your paper certificate pad, your scheduling whiteboard, your invoicing software, your GPS tracker, your phone system, and your filing cabinet.

Feature comparison

Score: Muster 22/22 — Gas Engineer Software 7/22

Gas Engineer Software covers the certificate essentials. Muster covers everything a gas engineering business actually needs to run.

Certificates: how they compare

This is where Gas Engineer Software built its reputation, so it's worth a detailed comparison.

Gas Engineer Software certificates:

• CP12 / Landlord Gas Safety Records
• Gas safety inspection records
• Boiler commissioning checklists
• Unvented hot water certificates
• Fault code database (useful for diagnostics)
• Pre-filled from job data

Muster certificates:

• CP12 / Landlord Gas Safety Records
• Gas safety inspection records
• Boiler commissioning checklists
• Unvented hot water certificates
• Custom certificate templates (build your own)
• Pre-filled from job data
• Sent to customer portal automatically

The core certificate output is comparable. Gas Engineer Software has a boiler fault code database that Muster doesn't (yet — it's on our roadmap). Muster has custom certificate templates and automatic delivery via the customer portal.

If all you need is CP12 generation, both platforms handle it. The difference is what happens before and after the certificate.

What happens before the certificate

With Gas Engineer Software, you schedule the job in their basic calendar, drive to site, and fill in the cert.

With Muster:

1. The job is quoted with line items, materials, and labour — sent to the customer for approval
2. The job is scheduled with drag-and-drop, assigned to the right engineer based on ACS categories
3. The engineer gets route-optimised directions via GPS
4. The customer gets an ETA notification with live tracking
5. The engineer completes the job and fills in the certificate on site
6. The certificate is saved and sent to the customer portal automatically

The certificate is the same. Everything around it is different.

What happens after the certificate

With Gas Engineer Software, you go back to the office (or sit in the van) and create an invoice separately. Chase payment manually. File the certificate somewhere you'll hopefully find it later.

With Muster:

1. The invoice is generated from the job — no re-typing
2. The customer gets a payment link via Muster Pay
3. Payment is tracked and your accountant sees it in Xero/QuickBooks immediately
4. If they don't pay, Muster chases automatically — email reminders at intervals you set
5. The certificate is filed in the job record, the customer portal, and available for landlord compliance audits

The certificate itself takes 5 minutes either way. The 45 minutes of admin around it is where Muster saves you time.

Pricing comparison

This is where the maths gets interesting. Gas Engineer Software uses per-user pricing. Muster uses flat-rate pricing.

Solo engineer

Winner: Gas Engineer Software. If you're a solo gas engineer who only needs certificates and basic scheduling, Gas Engineer Software is cheaper and does what you need.

Team of 5 engineers

Winner: Muster. For £29/mo more, you get 15 additional capabilities. That £29 pays for itself the first time Muster chases an overdue invoice for you.

Team of 10 engineers

Winner: Muster. And the gap narrows as you grow. At 15 engineers, Gas Engineer Software costs £450/mo. Muster Growth is still £349/mo.

Team of 20 engineers

Winner: Muster. At 20 engineers, Muster is actually cheaper — and includes every feature. Gas Engineer Software gives you certificates and a calendar.

The tools you're paying for separately

If you're on Gas Engineer Software and need the features it doesn't have, here's what you're paying for elsewhere:

For a 5-engineer team, the "cheap" cert app at £150/mo becomes £150 + £40 + £75 + £100 + £30 = £395/mo when you add the tools you actually need.

Muster Starter: £179/mo. All of it included.

What Gas Engineer Software does better

We said we'd be fair, so here it is:

Boiler fault code database — Gas Engineer Software has a built-in library of boiler fault codes. Useful when you're on site diagnosing an issue. Muster doesn't have this yet (it's on our roadmap for Q3 2026).

Brand recognition in the gas trade — They've been around longer and have 6,000+ users. If you ask a gas engineer what software they use, they'll likely mention Gas Engineer Software before Muster. That's earned through years of serving the trade.

Solo engineer pricing — At £15–30/mo for a single user, Gas Engineer Software is cheaper than Muster's £179/mo Starter plan. If you're genuinely a one-person operation who only needs certs, they're the more economical choice.

Who should stay on Gas Engineer Software?

• Solo gas engineers who only generate certificates and do basic scheduling
• Engineers who don't invoice (employed by someone else, just need certs for the jobs they do)
• Anyone happy with their current workflow and not looking to grow

There's nothing wrong with Gas Engineer Software if it does what you need. The problems start when you need more.

Who should switch to Muster?

• Any team of 3+ engineers — the flat-rate pricing makes more sense
• Anyone paying for separate invoicing, GPS, or phone answering — consolidate into one tool
• Growing businesses — per-user pricing punishes growth; flat-rate doesn't
• Engineers doing commercial work — RAMS, compliance tracking, and bid writing aren't optional
• Anyone chasing late payments — Muster Pay with automated invoice chasing saves hours per week

Migration

Switching from Gas Engineer Software to Muster takes under a week. Our onboarding team handles:

• Customer record import
• Job history migration
• Certificate data transfer
• Gas Safe and ACS registration setup per engineer
• Xero/QuickBooks connection

No data loss. No downtime. You can run both platforms in parallel during the transition if you prefer.