Frequently Asked Questions

Boilers have been historically oversized for houses, and gas,oil and LPG priced so low that we have not noticed how inefficiently they run. As boiler have have been so oversized they are very forgiving in their heat production. 

An air source heat pump however is a bespoke heating system designed specifically for your home to make sure it works effectively and efficiently. There are also a lot of additional items required for the installation and increased pipe sizes and fittings. This all adds additional cost to the installation.

The government have have created the Boiler Upgrade Scheme (BUS) voucher to help with the additional costs associated with a heat pump installation. The voucher is for £7,500 and is claimed through your MCS installer and deducted from the quotation provided.

Under the Energy Saving Measure (ESM) Initiative, the government has made a heat pump installation, all associated items and labour costs subject to 0% VAT rate.

A heat pump system can save you money, how much depends on the quality of your install. The full journey of installing a heat pump has an effect on the final efficiency. The vital steps to a quality install are:

> A good survey

> A correct heat loss

> A full specification and design

> A quality install

> A detailed hand over to you the homeowner.

Without each one of these steps being fulfilled with diligence, risks your heat pump being less efficient and costly to run.

Additionally, how you currently operate your heating will have an effect on the savings you could potentially make.

When Low Carbon Survey and Design Ltd provide you a quotation, this will include designed efficiency estimates, energy usage estimates and annual cost estimations under MCS guidelines.

Under MCS guidelines, we provide an accurate survey of the fabric of your property which enables us to correctly calculate how much heat your home loses.

A heat pump is a source of heat, and will provide the amount of heat specified in the manufacturers datasheets. 

The heat pump will be selected based on your heat loss to provide the correct amount of heat into your home.

If you are upgrading your property a "fabric first" approach should always be taken and you should always install as much insulation as practicable. This is the key to reducing your energy usage and in turn reducing your heating costs.

However, to say that additional insulation HAS to be installed is incorrect. Heat pumps have been successfully installed in grade listed buildings throughout the UK and even castles where insulation measures are impossible. As long as  the heat pump is designed to meet the specific heat loss of your home it will work.

It is important to  note that to gain access to any government funding you must have completed any insulation which is highlighted on your EPC and have the heat pump installed by an MCS accredited installer.

A heat pump works at low temperatures meaning that the temperature of your radiators will be lower than you are used to. This does mean that your radiators will be larger to transfer their heat into the room effectively. However, this does not mean they are going to be huge.

Interestingly building regulations changed in June 2022, meaning that if you were to install a new boiler heating system, the pipework and radiators would have to be sized to "future proof" the installation. Under these new building regulations the radiator and pipework would be the same size as a heat pump.

The average person showers at between 38°C and 42°C . With a low temperature heat pump your cylinder is stored at around 50°C meaning this temperature is still easily achievable. This is the most efficient temperature for your heat pump, but also the most cost effective.

Once a week the heat pump raises the temperature of the stored hot water with the help of the cylinder immersion heater to provide a Legionella disinfection cycle.

A heat pump transfers energy from outside, into your house using refrigerant gasses within the outdoor unit. Refrigerant gas can remove energy from the air down to -25°C.

An example of this is your fridge/freezer which is also a heat pump, removing heat from within the unit to keep your food chilled or frozen and distributing this through the metal pipes at the rear.

 To demonstrate that heat pumps are effective at colder temperatures, the biggest uptake of heat pumps (per 1000 of the population) in Europe are in Finland, Norway and Sweden which also benefit from the coldest temperatures on the continent. (Source : Financial Times)

A large contribution of a heat pumps efficiency is due to the higher flow rates at which they operate. Moving these larger amounts of water around your system require larger pipes to do this efficiently.

Optimum pipe sizes are specified at the design stage.

10mm pipe may be used in systems in very rare occasions, however this will reduce the efficiency of the system and complex calculations would have to be completed to ensure the system still runs effectively.

There are 2 main ways to optimise efficiency in your heat pump:

1: Low flow temperatures

The golden rule is; the lower the flow temperature of your heat pump, the more efficient and economic it is going to be. The optimum design (maximum) flow temperature for a heat pump is 45°C this is the "sweet spot" for radiator sizes, capital costs and running costs. 

The higher the system flow temperature the more it will cost to run, with as much as a 40% reduction in efficiency for every 5°C increase in flow temperature.

2: Weather Compensation

This is the direct correlation between the outside temperature and the flow temperature on the heat pump. You may need a 50°C flow of water to maintain a 21°C room temperature when it is -3°C outside. However if it was 9°C outside you would not need 50°C to keep the room at 21°C, this would be a waste of energy as the heat pump would switch on and off too often reducing the lifespan of the heat pump and costing more to run. So the heat pump regulates its flow to heat the room with extended running times which is more efficient. In this instance it would flow at around 36°C making your radiators luke warm to touch but still keep your rooms to 21°C.

The best every day example of this is driving your car around town, between speeds of 10mph and 50mph, changing gears and changing speed often uses more fuel than if you drive on a motorway maintaining a speed of 50mph in cruise control.