1-Minute vs 2-Minute Gas Rating: A Recent Change You Should Know About

by | Dec 27, 2023 | Doing Work, Technical Knowledge

British Gas and Gas Safe Register have recently run trials which suggest the 2-minute standard test time for metric gas rating is no longer necessary, releasing a new technical bulletin detailing the change

They suggest that halving the time to 1 minute bears no significant change on the accuracy of the test, and in some cases “gave a heat input to nearer that given by the manufacturer”. 

How this impacts your day-to-day work

As a gas engineer running from job to job and still trying to squeeze in time for paperwork, every second truly does count. 

The 2-minute test has been standard for more than two decades now, and we all know the feeling of painstakingly staring at a stopwatch until it hits zero. Combined with the frequency at which these tests are carried out, we’re talking about some significant long-term savings and a much easier test to carry out. 

The formula and the test itself remain almost entirely unchanged. The sole difference is that the time taken, and therefore gas used, are halved. Here’s what it looks like in practise:

((3600 (seconds in 1 hour) * (final reading – initial reading)(m³) * CV (kW/m³)) / test time (s)) / 1.1


((3600* 0.054 * 10.76) / 120) / 1.1 =15.85kW  (net)

If we were to change the test time to 1 minute instead of 2, it would look like this: 

((3600* 0.027 * 10.76) / 60) / 1.1 =15.85kW  (net)

Is a 1 minute test really as accurate?

According to British Gas and Gas Safe Register, yes. Many experienced gas engineers will have already known this (with some carrying out their own tests to prove it), but it’s nice to know that a 1-minute test is now industry standard and accepted. For younger and in-training gas engineers, this change should come as a nice surprise. 

We’re sure that both British Gas and Gas Safe Register have done their due diligence, but it’s always nice to see the results yourself. We decided to run some quick gas ratings:

If you use a gas rate calculator

For those using handy gas rate calculators, this should be no problem.

At Gas Engineer Software, we’ve recently updated our gas rate calculator app (for both Android and iOS) to include a toggle option so you can easily flip between a 1-minute and 2-minute timer, depending on your preference.

Next steps:

If you’ve been thinking about implementing software into your workflow to save time, here’s what you can do next: