It's an easy question for owner-occupiers to answer - they do - unless they can get a grant which is becoming more difficult.
For private tenants it's a question of negotiating with the landlord - some will agree to pay for a depreciated amount when the tenant laves.
For social housing tenants, there will be a clear policy in each case.
There are some things where it is almost always worthwhile for the tenant to pay - for example low energy light bulbs, when an old filament bulb needs replacing. The question then is what to replace it with? A relatively cheap compact fluorescent, or a more expensive but more efficient LED? This will depend on the relative costs. it is usually well worthwhile for the tenant to do basic draughproofing of doors and windows,
To find out what grants are available, a good place to start is the Governments own webpage on the subject,

