With ESOS Phase 2 upon us, minds nationwide are turning to the most efficient, effective and meaningful routes to compliance.

And among these, for many businesses, ISO5001 represents an appealing option. If your organisation is fully covered by ISO 50001, you do not need to carry out an ESOS assessment.

Here’s what you need to know about walking the ISO path.

ISO 50001 – energy management

It is true that for ESOS Phase 2, little has changed from the original ESOS scheme. The same remains true of the ISO path to compliance within the ESOS hierarchy.

The actual ISO guidance pages note that using energy efficiently helps organisations save money as well as helping to conserve resources and tackle climate change. ISO 50001 supports organisations in all sectors to use energy more efficiently, through the development of an energy management system. (It’s worth noting that the implementation of an energy management system was in the top 3 recommendations made by ESOS Lead Assessors in Phase 1.)

One could almost copy and paste this text to describe the goals of ESOS, so similarly are their strategies aligned.

What we need to understand is why ISO 50001 suits certain firms better than using an in house lead assessor, or employing a third party to manage compliance.


ISO takes time. Various estimates suggest the process should take about 6 to 12 months. Then again some consultancies out there who help firms meet ISO standards contract for a minimum of 3 years.

This hints that there can be challenges along the route. So, for firms suddenly realising they might want to meet ESOS through ISO, when time is short, this route isn’t practical.

Remember, under ESOS you have to ensure an audit is completed and energy saving opportunities are reported, or ensure an alternative compliance route such as ISO 50001:2011 – Energy Management System (EnMS) is implemented.

The wording of implemented is interesting in this case; don’t necessarily assume you can go to the regulator and argue that when your predicted ISO is certified and running in 4 months’ time, they should allow you leeway on ESOS on that basis.

The idea is to have ISO50001 done and dusted before ESOS hits.

Many firms who use ISO50001 for ESOS have already had the certification up and running for a while. That said, it’s logical that more firms should know about ESOS now it’s in the second phase.

So, more firms might be planning further in advance and picking the ISO fruit, building in time to make the grade.


Because it is a further reaching and longer term system than ESOS, it’s reasonable to expect ISO will cost you more to achieve in the short term.

Then again you are getting more for your money, and of course once the ISO system is in place you can use it again and again to comply with ESOS.

Actual wins

ISO will make you actually implement an energy management system. This means that in all likelihood, you will actually see costs dropping, energy use streamlining and many other performance, profit and environmental benefits.

Contrastingly, ESOS will make you report on energy, but it won’t force you to do anything about it.

In conclusion

The industry sense is that ISO is a great route if you have time, money and capacity, and are genuinely seeking long-term energy control and savings.

But, if time is short, and all you really want to do is comply with ESOS, ISO could be a bridge too far.