The right choice when air source isn't — and the wrong choice when it is.

Both extract low-grade heat and upgrade it with a refrigerant cycle. Air source takes heat from outside air; ground source takes it from soil or rock via underground pipework (a borehole array or buried slinky loops). Ground source has better year-round efficiency because ground temperatures don't swing the way air does — a UK borehole sits at roughly 10–12°C all year. The trade-off is upfront cost: ground source is significantly more expensive to install because of the ground works. For most modest UK homes, air source is the more cost-effective choice. Ground source comes into its own on larger properties and bigger commercial loads.

Two routes. Boreholes are vertical — typically 80–150 metres deep — and need a few metres² of clear access for the drilling rig but very little permanent surface area. Slinky or trench loops are horizontal, buried about 1–1.5 metres down, and need roughly 2–3 times your house footprint of clear land (no buildings, no large tree roots). For a 200m² home that means an area of around 400–600m². Most rural Scottish properties have one of those two routes available; many have both.

In most cases no — domestic ground source installations generally fall within Permitted Development in Scotland, as long as the array is below ground and the indoor plant is internal. There are exceptions: listed buildings, conservation areas, and some commercial sites can need consent. We'll flag any planning requirement at survey and, where needed, support the application or refer you to a planning consultant. The Home Energy Scotland grant is unaffected either way.

Plan for 2–4 weeks from first plant on site to commissioning, but spread across two phases. The ground works (drilling or trenching) typically take 1–2 weeks depending on the array size and access. The plant room install runs alongside or after that and takes 3–5 days. Most of the disruption is concentrated in the ground-works phase; the indoor work is no more invasive than a boiler swap.

Large rural homes where the higher upfront cost is justified by decades of lower running costs, properties where an outdoor air source unit would be visually or acoustically intrusive (listed, conservation, tight courtyards), and larger commercial loads where the peak heat demand makes the borehole investment pay back faster. For most three-to-four-bedroom Scottish homes on standard plots, an air source heat pump is the more cost-effective answer — and we'll tell you so honestly during the survey.

Two reasons. First, the ground works require specialist plant and partners — drilling rigs, trenching equipment, and the engineering knowledge to specify the array correctly. Second, the volume is lower: most installs done in Scotland are air source, so a lot of installers focus there and either contract the rare ground source enquiry out wholesale, or turn it down. We design and project-manage the full install ourselves, working with a trusted drilling partner for boreholes — the same accountability line as our ASHP work, from first survey through to commissioning.