Your heat pump questions answered by our experts

Whatever size system you install, your heat pump is bound to use electricity at times when your solar panels aren’t generating. You’ll need to use electricity from the grid to keep you warm during these times.

However, it may be possible to fit a solar panel system that generates as much electricity in a year as the heat pump uses. That way, your total generation matches your demand. This would depend on: 

• the size of your roof 
• how much heating your home needs 

The heat pump will often run at times when there’s little or no solar energy to use. This means you’ll be: 

• selling surplus electricity to the grid during the day in the summer
• buying electricity back to run your heat pump at night and in the winter 

If you add a battery storage system you can store surplus electricity during the day to run the heat pump in the evening. This will save you money because you usually get paid less for exporting electricity than you’d have to pay to import it from the grid. 

However, you can’t store excess from the summer to run the heating in the winter. So, you’ll always be using the grid to balance the energy you generate and the energy you use. 

The average size of a domestic solar panel system in the UK is about 3.5 kilowatt peak output (kWp). This should generate enough during the year to balance a heat pump’s requirements in a typical home. But every home is different and yours may have higher or lower heating requirements than this. 

You should get an engineer to service your heat pump according to the manufacturer’s advice, usually once a year. This is similar to a gas or oil boiler.  

Apart from that you should make sure the outdoor unit is clear of any obstructions such as: 

• bikes 
• wheelie bins 
• leaves 

This will ensure good air circulation, which helps the heat pump work more efficiently and reduces your running costs. 

An air source heat pump service typically involves: 

• an electrical safety check 
• checking the thermostat operation 
• a general visual inspection of the unit 
• refilling refrigerant (if needed) 
• checking for leaks/pressures 
• cleaning filters and coils 
• checking all large components such as the compressor, fan, and pump 
• lubricating moving parts 
• replacing any small parts such as seals and gaskets as per the manufacturer’s guidelines 

If you have a ground source heat pump the service should also include checking: 

• antifreeze concentration in the ground loop circuit
• flow and return temperatures in the ground loop circuit 
• pressure in the ground loop circuit  

Costs for heat pump servicing vary depending on the type of heat pump you have, but you can typically expect to pay around £150. You should service your heat pump every year. 

Heat pumps use electricity. So, if you’re replacing a gas or oil boiler with a heat pump, your electricity costs will increase significantly. At the same time, your gas or oil costs will reduce significantly. Therefore, it’s important that you’re on a relatively inexpensive electricity tariff.  

If you’re replacing a gas boiler, you should also consider removing other gas appliances. This means you can remove gas altogether from your home and don’t have to pay the standing charge for gas. 
 
If you’re replacing electric heating with a heat pump, your electricity costs should go down considerably. If you still have an Economy 7 meter, contact your energy supplier about switching to a standard rate meter. Economy 7 meters don’t work well with heat pumps as heat pumps often run throughout the day during the more expensive peak rate. 

Some electricity suppliers offer reduced rates if you have a heat pump as well as deals on the heat pump installation. So, check if you’re eligible and whether its worth switching energy tariffs.
 
It’s worth looking at a time of use tariff when getting a heat pump. This type of tariff offers you cheaper electricity prices when demand and energy prices are at their lowest. So, you may be able to set the water heating programme, and maybe even the space heating, to make the most of the cheaper electricity. 

Bear in mind that time of use tariffs charge more than standard tariffs at some times of day, so you could still be better off on a standard tariff. The main exception to this is if you have battery storage to help you manage when you take electricity from the grid. 

Heat pumps are more efficient when running at a lower temperature. They also usually store water at a lower temperature than you may be used to. This is fine because we generally need to mix our hot water with some cold to avoid scalding. Just remember that you may not need to do this anymore once you get a heat pump. 

The tank will also need to be slightly bigger than you’d use with a gas boiler – you’ll need more hot water to fill a bath or run a shower if you’re not mixing it with as much cold water.  Your installer should make sure the cylinder is the right size when fitting your system and should also make sure your hot water pipes are suitably insulated. 

There are a few other things you can do to make sure you heat your water in a way that’s cost-effective: 

• If you have a time of use tariff, set your water heating programme for whenever your electricity is cheapest. 
• If you have solar panels and a standard tariff, set your water heating programme for when your solar panels usually produce the most electricity. 
• If you have a standard tariff but no solar panels, set your water heating programme for the middle of the afternoon. This is generally when the outside air is warmest. 

Your hot water system will include a sterilisation cycle that periodically heats the cylinder to above 60°C to prevent bacterial growth. Make sure this programme runs at the cheapest time of day, just like your regular water heating programme. 

You shouldn’t have to do anything -the system should be set to vary the flow temperature according to the season. This makes sure it’s hot enough to heat your home during colder weather, but cooler during warm spells to make the system more efficient. This is called weather compensation.  

Your installer should set this up for you, but you may have the option to adjust the weather compensation settings.  You might even be able to override the system altogether. You shouldn’t make any changes to these settings unless you know what you’re doing. Your installer should be happy to help you if you think the system isn’t running well enough to meet your needs. 

If you have realistic options for improving your home insulation, it’s worth seeing if you can do this before or alongside your heat pump installation. There’s financial support available to help fund this, including the Great British Insulation Scheme. 

Whether you’re able to upgrade your insulation or not, your heat pump installer will design a system to match your expected heating needs. 

If your home’s insulation is poor and your heating demand is high, you likely need bigger radiators throughout the property. You might even need an extra one here and there. This is how heat pumps manage to heat poorly insulated buildings without having to work harder than they need to. If your installer offers to upgrade your radiators and you want to avoid any nasty fuel bill surprises, you should say yes.  

The same tips apply here as with any heat pump. But with poorly insulated homes, they’re even more important: 

• Keep the heating running at a steady level rather than turning it up and down all the time. 
• Set your heating controls to come on earlier in the morning so the house has time to heat up before you get up 
• If your home is empty during the day, set the programmer to turn the heating down a bit rather than off altogether. Then, set the heating to come back up to temperature before you get home. 
• Don’t worry if the radiators don’t feel all that hot – they’ll still heat the room up if you leave them on for long enough.  

Heat pumps come with a programmer and thermostat to control your heating, plus a lot of other options for controlling the heat pump itself. Your installer should set everything up for you, after asking you about your heating preferences. 

Some heat pump settings are best left alone unless you know what you’re doing. But you can still adjust the programmer and thermostat to meet your heating and hot water needs. They do the same job as the controls for a gas boiler. But they probably look and feel different to what you’re used to, so make sure the installer explains how they work.  

Provided the installer has set them up right, you shouldn’t need to make any changes to your heat pump’s controls. Many of the controls are there to make sure the system can adjust itself to meet changing conditions, so you don’t have to adjust yourself. 

If you’re not sure, ask your installer to check them and discuss any issues you may be having with how the system is running. 

Historically we’ve seen issues with poor quality installations in UK homes, including where installers don’t: 

• size systems correctly 
• upgrade radiators
• replace narrow bore pipework
• properly insualte pipework  

As standards have tightened, equipment has improved, and the supply chain has matured these issues are much less common. 

However, it’s always worth checking the pipework insulation to see if anything has been missed or has settled over time. 

Once your system is installed correctly, you’re not likely to see much in the way of equipment failure. In fact, the heat pump itself is likely to last 20 years or more – that’s longer than the average gas or oil boiler. 

Any issues you meet with performance are most likely to come from the way the system is set up and how you use it. If you try to run your heat pump as though it were a gas boiler rather than following manufacturer’s instructions, you may experience poor performance. This will likely lead to: 

• unexpectedly high electricity bills 
• poor comfort levels 
• increased risk of equipment failure 

Electricity costs around four times as much as gas. A typical new gas boiler will run at around 85% efficiency, and an older boiler that’s due for replacement will average more like 75% efficiency. 

But heat pumps tend to run with a seasonal performance factor (SPF) of 3.1. This makes them around four times as efficient as a gas boiler, maybe slightly more. This is why the two systems can have similar running costs at current prices. 

However, a good quality heat pump installation that you manage well and control appropriately can get an SPF significantly higher than 3.1, sometimes more than 4. If this is possible you should be able to save money compared to even the most efficient gas heating system. 

Assessors base the main rating on an Energy Performance Certificate (EPC) on the expected running costs of the home. 

As heat pumps often cost a similar amount to run as gas, your EPC rating is likely to stay roughly the same. It could end up slightly lower or even higher depending on the system details and the assumptions the EPC assessor makes. 

All EPCs also have an environmental rating, and this rating will always improve dramatically if you switch from gas to a heat pump. 

The UK Government is considering several options that might affect how heat pumps affect EPC ratings. These include: 

• changes to energy pricing 
• developing new calculations and approaches for producing EPCs 

In the UK we’re seeing a lot of air-to-water heat pumps going into homes, together with a few ground source systems.  

In other countries, air-to-air heat pumps are more common. We expect to see increasing interest in this technology in the UK because of its: 

• potential to provide cooling as well as heating 
• ability to work in homes with limited space 
• suitability for homes without an existing radiator system

There are emerging technologies that can be fitted entirely inside the building, including both air-to-water and air-to-air systems. This makes them ideal for homes that have no room at all for an outside unit, such as a mid or top floor flat. These technologies include some technically well-established models alongside some newer innovations, but there’s currently not a very active supply chain in the UK. 

Also the extreme difference in price between fuels limits the heat pump roll out in Great Britain. Currently, electricity costs around four times as much as gas. 

This is more than in other countries and is partly due to artificial distortions in British energy prices. The government is aware of several options for removing this distortion. As soon as it does something to balance things out, we expect to see: 

• a rapid increase in heat pump adoption 
• the start of a move away from subsidised installations (like the Boiler Upgrade Scheme) 
•  a broadening of the range of technologies available 

We’ll be keeping a close watch on developments in heat pump technology and government policy.