First, check your tenancy agreement carefully.  Does it prohibit either this specifically or prohibit any alterations at the property?  Most tenancy agreements will have some sort of clause along those lines which will catch changing the meters without actually referring to them by name.  

If this is the case, then you will need to get your landlord’s permission.  

Note that if this is refused and you go ahead and change the meters anyway, your landlord will be entitled to claim from your deposit the cost of changing back to a ‘pay-as-you-go metered supply at the end of the tenancy.

If you do not have a written tenancy agreement, then there will be no prohibition, so you will be able to change over.  But note that if you have signed a tenancy agreement in the past, and your tenancy has run on as a periodic tenancy, the terms of this written agreement will still apply now.