Technology Comparisons

Unlike air source heat pumps, the inherent efficiency of ground source heat pumps means they can deliver the lowest running costs of any type of heating system and the best return from the RHI, giving you payback on your investment typically in 5 or 6 years.

See the benefits of ground source heat pumps when you compare a ground source heat pump vs air source heat pumps, oil, LPG, or biomass boilers, and weigh up ground source heat pump pros and cons.

Ground source heat pump vs air source

Air source heat pump issues:

  • Winter time efficiency affected by cold weather;
  • Running costs go up when you need heating the most!;
  • Output reduces with air temperature;
  • Needs planning permission due to noise;
  • Exposed to the outside elements;
  • “Real” outputs limited to ~11kW limits potential to smaller homes.
air source heat pumps issues compared to ground source heat pumps

Air source considerations

An air source heat pump’s lower upfront capital cost may seem appealing, but the lower RHI income and the higher running costs will often mean any upfront saving is quickly negated.  And the unobtrusive nature of a ground source heat pump installation is usually a significant attraction as is the superior durability and reliability that results from locating the heat pump within a weather-tight structure or inside the property.

Multiple studies across Europe demonstrate that ground source heat pumps are typically around 20% more efficient than air source heat pumps. This is entirely understandable as the average ground temperature throughout the winter heating season is higher than the average air temperature which means the heat pump does not have to work as hard to upgrade the source heat into something useful for space heating and hot water.

Why consider a ground source heat pump?

In brief, a ground source heat pump will:

  • Provide 100% of heating and hot water requirements;
  • Operate 365 days a year;
  • Reduce running costs by as much as £500;
  • Generate a generous income through the Renewable Heat Incentive;
  • Eligible for the Cleaner Heat Cashback Scheme;
  • Minimise ownership costs;
  • Last for 25 years, with a 100 year ground array lifetime.

All of this, and with the added benefits of:

  • No planning permission required;
  • Quiet operation;
  • Safe and easy to operate;
  • Simple to install;
  • No risk of vandalism or theft;
  • No noxious gasses or risk of combustion;
  • No point of use emissions such as Nitrogen Oxides (NOx), Sulphur Oxides (SOx) or Carbon Dioxide (CO²)
  • Can be used to provide passive and active cooling.

Ground source considerations

A ground source heat pump’s superior efficiency compared to an air source heat pump’s is only half the story. It is very likely that future electricity tariffs will feature split rates depending upon when the electricity is consumed.  Almost certainly, the lowest tariffs will be available for night-time operation when there are lesser demands. The challenge will be to find ways to shift a household load to these periods. An immediate option would be to re-charge the hot water cylinder through the night. A future option might be to store heat perhaps utilising phase change materials.

Either way, an air source heat pump usually operates at its lowest efficiency through the night since the air temperature is usually significantly cooler at 2am than 2pm. Plus the noise of the circulation fan will not aid sleep.  Meanwhile, the prevailing air temperature does not impact the performance of a ground source heat pump since the ground arrays are buried at sufficient depth to be insulated from these variations.

Ground source heat pump vs Biomass, oil & LPG

Oil & /LPG issues:
  • Unsightly fuel storage tank;
  • Highly flammable;
  • Hassle of organising fuel deliveries;
  • Possibility of fuel theft;
  • Pay for the energy upfront all in one go;
  • Complicated installation compared to ground source;
  • Contributes to air pollution through the emission of particulates, Nitrogen Oxides (NOx) & Sulphur Oxides (SOx);
  • Not eligible for Cleaner Heat Cashback Scheme.
Biomass issues:
  • Space required for fuel storage;
  • Forces reliance on regular fuel deliveries;
  • High maintenance compared with ground source heat pumps;
  • Planning permission required due to emissions;
  • Contributes to air pollution through the emission of particulates, Nitrogen Oxides (NOx) & Sulphur Oxides (SOx);
  • Not eligible for Cleaner Heat Cashback Scheme.

Replacing oil

For older properties which are not especially well insulated, Kensa needs to establish whether the existing heating system and existing insulation levels will be compatible with a ground source heat pump.

Winter is the best time of the year to trial your property for it’s suitability for a ground source heat pump.

To do this, turn down the flow temperature of your existing boiler to 50°C and run the system through this winter heating season to mimic the output of a ground source heat pump system.


If you find you can maintain your required comfort conditions at this lower flow temperature, then you have proved that that your existing heating distribution system and the current heat loss of your property is compatible with ground source heat pump installation.

Once you have carried out this exercise through the winter and you are satisfied with the internal temperature of your home, please contact Kensa to discuss your ground source heat pump installation in further detail.

For modern, well insulated properties, we would be able to prepare a quotation for you immediately as we are confident that your required internal temperatures could be reached using a ground source heat pump.

Having a ground source heat pump means the property is much more energy efficient and less reliant on fossil fuels.

Alistair Mackintosh, Selfbuilder

The savings on our energy bills compared with oil is fantastic and our house value has increased as a result of the installation - we’re over the moon!

Stephen Chidgey, Homeowner