Hi @ellyse and welcome.

Your question is going to need responses from a number of us.
I'm from a technical background, so I'll stick to those aspects.

1: Any heat-pump installation starts with an energy survey of the house, which identifies:

• the overall heat loss from the house (which dictates the amount of energy required to maintain its temperature)
• the heat required per room (from which the size of radiators is calculated)

Those figures are static. They don't vary according to outside air temperature or what season of the year it is.

The installer can then design a system which can deliver that amount of 'space heating' and also supply domestic hot water (DHW) from a cylinder.

2: The DHW cylinder will also have an electric immersion heater in it.
That's not 'efficient' but is necessary for a number of reasons:

• if the external part of the heat-pump should ice up in winter, there needs to be a way for the system to de-ice it
• if the temperature of the DHW falls, then there's a risk of Legionnaires Disease. The immersion-heater gets switched on periodically to raise the temperature high enough to kill the bacteria

These functions are automatic. You don't have to do anything about them.

3: Since there is an immersion heater, that leaves open the possibility of using solar electricity to heat DHW during the summer months, rather than have the heat pump running.

There are systems called Load Diverters which achieve this.
The chosen method depends on whether the inverter for your solar panels also has the capability to store electricity in a battery.

The possibility of having battery storage is more important that the solar panels.
Those households with batteries can take advantage of Time-of-Use Tariffs all through the year.
You only import electricity from the grid at times when it is cheapest.

Even if the Government Scheme doesn't include a battery, it is important to ask if you can have a solar-inverter which allows you to add one later at your own expense.

@ellyse how do you currently heat hot water? 

The answer to your question is very likely 'no more than than at present' but does depend slightly on thow you currently heat hot water.  Please post this answer for an accurate response and suggestions.

Right now we have an Immersion heater for hot water and electric heaters in each room for heating.  During summer we rely on electric fans to stay cool. 

The grant will allow us to have solar panels, plus heat pump, plus large water tank in 2 parts for heating and water, plus radiators in every room.  All free. 

We live in a small bungalow, on a mini-estate of over 55 yr old only accommodation. 

Posted by: @ellyse

↑

Right now we have an Immersion heater for hot water and electric heaters in each room for heating.  During summer we rely on electric fans to stay cool. 

The grant will allow us to have solar panels, plus heat pump, plus large water tank in 2 parts for heating and water, plus radiators in every room.  All free. 

We live in a small bungalow, on a mini-estate of over 55 yr old only accommodation. 

To answer your previous question, a heat pump can be used to provide thermal energy for both central heating and DHW, but not both at the same time. In Summer the heat pump can provide DHW without heating your home, other than the small amount of thermal energy that 'leaks' through the insulation on the pipework and hot water cylinder.

Because you are also having a solar PV system installed, you could consider installing a power diverter such as an iBoost, Eddi or similar. This device can be used to divert the excess solar PV generation to your immersion heater to produce hot water. The benefit of such a device is that it should provide most of your hot water, totally free, from Spring through to Autumn without the need for the heat pump to run.

The quality of the installation is extremely important @ellyse 

A heat pump doesn't work like a gas boiler.
It stays operating all the time, adjusting the water flow to accommodate the need for heat.

In comparison, a boiler gets switched on/off by temperature sensors.

The water produced by the heat pump will be only about 45°C.
It requires large radiators to raise the air temperature in the room.

If the installer runs pipes below the floor and doesn't properly insulate them, then most of that heat will have disappeared by the time it reaches the radiators.

The consequence of poor quality installation is high running costs.

It doesn't matter if the equipment was free if you can't then afford to run it!

Who is administrating the scheme?
Is it a national organisation or your local Council, for example?

Posted by: @ellyse

↑

My home gets very hot in the summer. We have large patio doors that work like a greenhouse so we don't use heating from May to November typically.  Right now my home is getting temps between 23C and 26C inside with only the sun on the patio doors. So how will heat pump heating work for hot water without increasing the temp in my home? The last thing I want is more heat in the summer. 

So to answer the specific question you asked - no the ashp won't heat up the house when it is heating the water because separate pipes are run to radiators and dhw cylinder.  Just like you can heat dhw in summer with a gas or oil boiler without simultaneously heating the house!

Your storage cylinder will lose some heat to the house, but that's the case currently with your immersion/storage arrangement.

The pipes between the ashp and the cylinder will also lose a little heat to the house but provided they are insulated the amount is negligible, much less than the heat emitted by a small piece of electrical equipment like a laptop or tablet.

So not something you need to worry about.

The comments made by others about quality of installation do of course apply.  However I wanted to give a focussed answer to your specific question.

Thank you James.   We never notice immersion heater heat as that is in the loft, but was installed when the place was built back in the 1980's.  The loft hatch is too small to get any tank in or out so heat pump tank will be in the back bedroom instead.  It is good to hear we need not worry about that as a problem. It sure seems an amazing offer well worth grabbing to get all this free. Only thing I think may be missing is battery storage for the solar. They have already started installing the 1st wave and we can see that some are getting 10 solar panels but others only getting 7 or 5 due to roof configuration. I'm hoping for 10 but anything free is good 🙂 

@transparent   Local council scheme with OVO controlling it. No pipes to go underground as we have concrete floors. They will have to be attic and down the surface of the walls with plastic trunking.

Posted by: @ellyse

↑

The loft hatch is too small to get any tank in or out so heat pump tank will be in the back bedroom instead

That's a bit six of one and half a dozen of the other.  In summer you might notice extra heat in the bedroom due to the heat lost from the tank.  In winter any heat lost isn't because it heats the house.  Most, given the choice, put the tank within the insulated envelope of the house to retain the heat.

Dhw tanks emit about 1-2kWh per day ie 40-80W.  So roughly equivalent to the heat emitted by an old incandescent lamp (most of the energy from which is emitted as heat) or a small person. Basically not a lot!

I would say (if you go ahead) don't worry but if you can put the tank in a cupboard (the top of which you can use for airing recently washed laundry.

@ellyse In 2021 OVO was one of three Energy Suppliers selected to administer the installation of heat pumps in 750 homes. OVO was assigned the SE England region with 250 dwellings, statistically chosen to represent the UK housing stock.

The £14.6m Electrification of Heat Trial was funded by the then Business Energy and Industrial Services Dept (BEIS), and implemented by the Energy Catapult. The Program Manager at BEIS was Alex Hobley.

I was then an OVO customer, and was granted permission to assist Trial Participants in a private sub-section of the OVO Forum.

That allowed those householders to request guidance and share data confidentially, without compromising the trial itself.

The Trial was plagued with administrative and technical difficulties.
The installers selected for the work had next to no experience of heat pump installation.
The largest of the installers (a major national energy company) had their contract curtailed, which is as close as you can get to the phrase "dismissed for incompetence".

Heat Pump manufacturers/suppliers were so upset with the installation work that they sent in their own senior engineers to inspect houses where their equipment had been installed. They produced strongly-worded reports which identified a catalogue of system-design and installation errors. A large proportion of the installations had to be re-plumbed, and in some cases, completely disassembled and the work started again.

I still retain scores of photographs showing improperly installed equipment.

Very few of the homes had lower energy bills as a result of their 'free' installations.
That was despite each property having £4000 available for fabric upgrades to increase the building's energy efficiency.

Most of those Trial Sites were being changed to Air Source Heat Pumps from previously having a gas boiler.
Participants who couldn't afford to pay the new/higher electricity bills were not permitted to have a gas boiler re-installed.

One of the biggest issues which emerged from this Trial was the inadequacy of the pre-installation process:

• Householders were not properly informed of what was to be installed or the likely running costs
• Many of the initial energy surveys were 'incomplete' and did not properly assess the true status of issues such as loft insulation
• The installers didn't understand the processes required to commission the new heat-pump system
• Documentation was inadequate and householders left with insufficient knowledge of how to operate the new heating system

The headline of the Energy Catapult 'Report' on the Electrification of Heat Trial was:

I could have written that simply by reading the manufacturer's specifications, without needing to spend £14.6m

But since electricity costs three times more than gas per kilowatt-hour, then the best you could expect to do is pay exactly the same as before.

That's why I'm asking so much about what is being proposed for your 'free' heat-pump installation.

It is certainly possible to get these heat pumps installed properly now.
Many installers have learned from past mistakes, and now have experience of what is required

But it is essential for us (the general public) to also learn from the errors highlighted in the Electrification of Heat Trial.
That means we should start learning what is being proposed even before the initial energy survey gets done.

Please share this information with your Local Council and allow experts here to provide guidance on 'good practice'.

Posted by: @transparent

↑

Many installers have learned from past mistakes, and now have experience of what is required

Sorry I cannot agree, major installer like Octopus seems to routinely specify systems with a design temperature of 50 to 55. Running costs are simply going to be ridiculous - justification is you can a tariff that makes it cheaper to run. People only really get away with lower running temperatures if the heat loss survey is done badly and the calculation shows a bigger heat loss than there really is.

Installs are zoned to death, if installer is left to make their own decision, then have buffers or low loss header etc which again impact efficiency.

Sorry it still a case of being knowledgeable customer or beware and have deep pockets for the bills.

The trouble with the "you get it for free" schemes the customer isn't right, doesn't have a say, you get what, we want you to have.

Posted by: @ellyse

↑

we can see that some are getting 10 solar panels but others only getting 7 or 5 due to roof configuration. I'm hoping for 10 but anything free is good 🙂

Good example by OP, they have no idea how many PV panels will be added to their roof!