The simple answer is NONE, we will be installing the same boilers and same controls we always have and homeowners will be facing the same energy costs as they did before ErP, it is absolute nonsense for anyone to claim the ErP will reduce homeowners bills.
Some of the figures that get banded about, 30%, 40% energy savings are in my opinion just blatant lies, a modulating pump and some extra controls will not reduce your running costs by 40%, running your heating at a lower room temperatures and improving your homes insulation levels will do far more to save on energy bills than expensive controls or a new boiler and just because a boiler now has a label saying it is A rated, (which they have been for 10 years, or have we been lied to) will not make any difference to energy costs.
We now have to complete a Fiche if we install a boiler and controls, or add solar etc, the Fiche is to give an energy rating to the "system", although it takes no notice of the, heat loss, heat emitters, or the insulation levels of the property, so I fail to see how it can be energy rating the system, but lets ignore that for now, what is the actual benefit to rating the system A or A+ well we would be told fuel savings, but how much? will the extra costs of controls that can move the system from A to A+ be worth the additional capital outlay by the homeowner, I am not so sure.
As installers the main thing we need to be aware of when deciding on controls is, if you want to make the system A+ and you are using external controls, not the manufacturers controls, then these controls MUST communicate with the boiler to control its modulation and temperature and this is not possible with all boilers, lets take Honeywell for example, only because they are one of the main control manufacturers installers use, now they have the Evohome system, quite a nice system, if as the homeowner you want to control your rooms or zones at different temperatures and times, now it is been said that adding the Evohome to a new boiler install will give the system rating via the Fiche an A+, well yes, BUT not quite as simple as that, wiring the Evohome as most have up to now, using the switch live from the wireless relay box to the boiler WILL NOT make the system A+, as this is just switching the boiler ON & OFF, to achieve A+ the Evohome has to communicate directly with the boiler, to do this you have to use the communication protocol Honeywell uses, which is Opentherm, this is a very good system, but unfortunately quite a lot of boilers don't have Opentherm in their boilers, so you would have to ensure that the boiler you are installing has the Opentherm capability built in, you then need the Honeywell Opentherm bridge and when connected the Evohome now modulates the boiler based on the demands from the zones, and so becomes the boiler control, this will be the same with any other control you use, to get the control to the class that allows you to move the system to an A+ it does not matter how smart the controller says it is, it has to be connected to the boiler correctly to use it in the higher Class rating.
Moving into the control Classes, we have even more nonsense from what I can see and what I have heard, the classification of some controls make no sense, in case you are not familiar with the classification of the controls, we have Class 1 - Class 8 each class takes the controls ability to function with the boiler to reduce energy consumption, Class 1 would be your standard on/off room stat and class 8 would be the Honeywell Evohome with Opentherm communication with the boiler and 3 or more zones. The classes add a % of efficiency, so controls in Class 1 are said to add 1% to the efficiency, Class 2 add 2%, Class 3 adds 1.5%, Class 4 adds 2%, Class 5 adds 3%, Class 6 adds 4%, Class 7 adds 3.5% and Class 8 adds 5%, now to get your boiler from A to A+ the only classes of controls that will do this are 6,7 & 8, but the difference in what these controls do is huge, so it is quite unfair that they achieve the same Energy rating via the Fiche. Now weather compensation on its own is not permitted and actually contravenes UK building regulations, it must have an internal temperature sensor as well, but if we take this type of control, when added to a boiler with an efficiency sufficiently rated so when the % of control efficiency is added takes it high enough to make the system rating via the Fiche A+, but what about zoning, once you start zoning you lose 100% weather compensation, boiler manufacturers will start pushing their own controls, but these tend to be weather compensation with internal sensor but if the property is over 150m2 it has to be zoned under Building Regulations, so what happens to the controls when zoning is added, will this effect that Class of the controller via the ErP, because at the end of the day, we as the installers will be the ones taking the responsibility, but we will only be adding data supplied by others
How exactly will the ErP be policed, or will it be the usual, installers who comply, as they want to do things right and installers who ignore it and just don't care, just want the money and go, and we will I am sure get those who give a system label showing A+ or even A++ when the system is not actually in that bracket, as you can put anything into the ErP tools I have seen on manufacturers websites, you don't have to be registered to use the tools