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How to Survey the Electrical Route for a Heat Pump
A practical guide to recording the electrical starting point and physical route to the outdoor unit.
- Last updated: September 2026
- Heat Loss Hub · For Installers
A heat-pump electrical survey should record more than the consumer unit. The designer and electrician need to understand how the electrical supply could physically reach the proposed outdoor unit.
A useful survey should record consumer-unit position, meter and visible supply information, existing major electrical loads, possible cable route, internal and external sections, approximate route length, wall, floor and ceiling penetrations, installation obstacles, possible outdoor isolator area, nearby electrical equipment, customer constraints, photos and video, and any information that remains uncertain.
The survey should provide enough reliable evidence for the electrical installation to be assessed properly afterwards.
Do not survey only the consumer unit and the heat pump. Survey the route between them.
KEY TAKEAWAY
The survey records the route. The electrician designs the circuit.
GET IN TOUCH
Send us the completed electrical-route survey alongside the wider project and we’ll factor it into the design.
What Information Should Be Recorded?
| Information | Why It Matters |
|---|---|
| Route reference | Keeps alternative electrical routes traceable |
| Consumer-unit position | Establishes the electrical starting point |
| Meter and supply evidence | Supports later supply assessment |
| Existing major loads | Shows what is already connected |
| Internal route | Shows how the cable may travel through the property |
| Exit point | Identifies where the route leaves the building |
| External route | Shows how the cable may reach the outdoor unit |
| Approximate route length | Supports later circuit design |
| Penetrations | Highlights installation complexity |
| Obstacles | Identifies difficult or disruptive sections |
| Isolator area | Shows where external isolation may be practical |
| Nearby electrical equipment | Supports product-specific siting checks |
| Customer constraints | Prevents technically possible but unacceptable routes |
| Photos/video | Provides supporting evidence |
| Confidence | Separates confirmed information from assumptions |
A useful electrical survey should create a route, not just a photograph of the consumer unit.
Use Candidate Electrical Routes
There may be more than one practical route between the electrical supply and the outdoor unit. Record each realistic option separately.
For example: ELEC-ROUTE-01 — Hall consumer unit → utility room → rear wall; ELEC-ROUTE-02 — Hall consumer unit → loft → side elevation → rear wall.
The routes can later be compared for length, access, number of penetrations, internal disruption, external exposure, customer preference and installation difficulty.
The shortest route is not automatically the best route. A slightly longer cable run may avoid tiled walls, fitted kitchens or significant internal disruption.
KEY TAKEAWAY
Difficult properties may need candidate electrical routes, not one assumed route.
Record the Consumer-Unit Area
Start by recording the electrical starting point. Useful information includes consumer-unit location, full front view, visible circuit labels, spare ways where clearly visible, adjacent wall space, existing sub-boards, meter position and nearby electrical equipment.
Photograph the complete consumer unit rather than only one section.
If there appears to be a spare way, record it as evidence. Do not treat it as confirmation that the consumer unit is suitable for the heat pump.
KEY TAKEAWAY
A spare way is useful survey information, not electrical approval. The electrician still needs to assess the existing equipment, circuit arrangement and protection requirements.
Record the Existing Supply Evidence
Where safely visible, record single-phase or three-phase supply if confirmed, main incoming fuse rating, meter details, MPAN where available, existing sub-main arrangements, other consumer units, solar PV, battery storage and EV charging equipment.
Do not remove covers or open sealed equipment to obtain this information.
If the fuse rating or supply type cannot be confirmed safely, record it as unknown.
KEY TAKEAWAY
The survey records the electrical starting point. The electrician decides what the supply can support.
Record Existing Major Electrical Loads
A heat pump is being added to an electrical system that may already contain significant loads. Record visible or known equipment such as EV charger, solar PV, battery storage, electric shower, immersion heater, electric heating, existing heat pump, air conditioning, hot tub, and other substantial fixed electrical loads.
The aim is not to calculate maximum demand during the survey. The aim is to make the existing electrical situation visible to the person carrying out the later assessment.
Record what is already connected before making assumptions about what the supply can carry.
Trace the Internal Cable Route
Follow a realistic path from the consumer unit toward the proposed outdoor-unit location. Record where the cable could pass through hallways, utility rooms, cupboards, garages, loft spaces, floor voids, ceiling voids, service risers, existing ducts, existing trunking and internal walls.
Also record difficult sections such as tiled walls, fitted kitchens, built-in wardrobes, solid floors, finished ceilings and recently decorated rooms.
Do not assume that the shortest line on a plan is physically usable.
KEY TAKEAWAY
Survey the route the cable can actually take, not the route that looks shortest on the drawing.
Record the Building Exit Point
Identify where the cable could realistically leave the building. Record proposed exit position, wall construction, existing service penetrations, internal access, external access, nearby heating pipework, nearby drainage, internal finishes, external finishes and any obstruction.
A route that looks easy from outside may be difficult internally. Likewise, an apparently straightforward internal route may emerge outside in an unsuitable position.
KEY TAKEAWAY
A cable route changes character where it passes from inside to outside.
Trace the External Cable Route
Continue the route from the building exit to the proposed outdoor unit. Record external wall route, ground-level route, existing conduit, existing duct, corners, doors, windows, rainwater pipes, cladding, other services, areas vulnerable to impact or damage, and approximate distance to the outdoor unit.
Do not assume external cabling can simply follow the shortest line. Consider accessibility and how the route interacts with the rest of the installation.
KEY TAKEAWAY
The shortest electrical route is not always the most practical route.
Measure the Approximate Route Length
Record the route in useful sections. For example: consumer unit to building exit — 6m; building exit to proposed isolator area — 5m; isolator area to outdoor unit — 1m; approximate total route — 12m.
Include vertical rises and changes in level. A route through a loft and down an external wall may be considerably longer than the plan distance between the consumer unit and heat pump.
KEY TAKEAWAY
Measure the route length; do not turn the survey into a cable-sizing calculation. Cable size, cable type and voltage-drop calculations belong to the electrical design.
Record Penetrations and Installation Obstacles
A useful route survey should record what the installer may need to pass through or around. Examples include brick walls, stone walls, timber-frame walls, tiled surfaces, kitchen cabinets, built-in furniture, solid floors, finished ceilings, loft insulation, external cladding, conservatories, extensions, and shared or communal areas.
Where a route depends on an uncertain construction, record that uncertainty.
A straight line on a floor plan may be a very different route through the building. This information can also help prevent unexpected installation costs later.
Survey the Proposed Outdoor Isolator Area
The survey should record a practical area where external isolation might be possible. Record available wall space, position relative to the heat pump, nearby doors, nearby windows, pipework, drainage, service access, cable entry point and existing external electrical equipment.
Do not use the survey to specify the final isolator location or product. That should be confirmed as part of the electrical and product-specific design.
KEY TAKEAWAY
Survey where an isolator could go before deciding where it should go.
Record Nearby External Electrical Equipment
The area around the proposed outdoor unit should also be recorded. Look for external sockets, external lighting, switches, existing isolators, junction boxes, other switchgear, EV charging equipment, solar PV equipment, battery equipment and other electrical services.
This becomes particularly important where the selected heat pump has product-specific requirements relating to nearby electrical equipment or ignition sources.
Do not apply one generic exclusion distance to every heat pump.
KEY TAKEAWAY
Record nearby electrical equipment first. Apply the selected heat pump’s product-specific restrictions during design.
Consider the Relationship With the Outdoor-Unit Survey
The electrical route should not be surveyed independently of the heat-pump location. The proposed outdoor position determines where the cable needs to reach, where external isolation may be located, how much external routing is needed, what nearby electrical equipment may need reviewing, and which wall or building exit is most practical.
KEY TAKEAWAY
The electrical route and outdoor-unit location should be surveyed as parts of the same installation, not separate decisions.
For the wider outdoor-unit survey:
Record Customer Constraints
A technically possible cable route is not automatically an acceptable one. Record customer preferences relating to visible external cabling, decoration, recently completed work, protected areas of the property, preferred routes, and any rooms or finishes they would prefer to avoid disturbing.
A route that is technically achievable may still create an unacceptable outcome for the household.
KEY TAKEAWAY
The technically shortest route is not always the customer’s preferred route.
Photos and Video
Good photographic evidence helps someone who has not visited the property understand the proposed route. Useful photographs include complete consumer unit, meter, existing major electrical equipment, internal route sections, potential exit point, external route sections, proposed isolator area, and the outdoor-unit position from the perspective of the electrical route.
Video can be particularly useful for showing how the internal and external sections connect together. For example: “This is the consumer unit, the cable would run along this wall, exit here, and reach the heat pump position along this route.”
For general survey photography guidance:
Remote-Survey Electrical Safety
Where a homeowner is completing part of the survey remotely, keep the request strictly to safe, visible evidence. Suitable requests include photograph of the closed consumer unit, photograph of the meter, photograph of the general area, and video of the possible cable route.
Never ask a homeowner to remove covers, open equipment, touch electrical components, or investigate anything beyond what is safely visible.
KEY TAKEAWAY
A remote electrical survey should never turn a homeowner into an electrician. Any further electrical investigation should be carried out by the appropriate competent person.
Use Measurements, Not Assumptions
Where practical, measure rather than estimate. Useful measurements include approximate route length, distance between consumer unit and exit point, distance between exit point and outdoor unit, and relevant clearances around the proposed isolator area.
Avoid relying on statements such as “It’s not far,” “There’s definitely a spare way,” or “The cable can just go along here.”
Where something cannot be confirmed, record the uncertainty rather than assuming a convenient answer.
KEY TAKEAWAY
“It’s not far” is not a survey measurement.
Confirmed, Inferred or Unknown
As with the rest of the heat-pump survey, it is useful to record how reliable the route information is.
Confirmed
Measured or clearly observed.
Inferred
Strongly indicated but not completely verified.
Unknown
Cannot be established from the available evidence.
For example: Route through utility room — confirmed. Route beneath ground-floor void — inferred. Wall construction at proposed exit point — unknown.
KEY TAKEAWAY
Hidden or uncertain sections should remain visible as uncertain until they are verified.
Example Electrical-Route Record
A completed record might look like this:
| Field | Example |
|---|---|
| Reference | ELEC-ROUTE-01 |
| Consumer-unit location | Hallway |
| Spare way visible | Yes (not confirmed suitable) |
| Existing major loads | EV charger |
| Internal route | Hallway → utility room |
| Internal obstacles | None significant |
| Exit point | Utility rear wall |
| External route | Rear wall to proposed unit |
| Approximate total length | 9m |
| Penetrations | 1 external wall |
| Isolator area | Adjacent to proposed unit |
| Nearby electrical equipment | External socket 1.5m away |
| Customer constraint | Avoid newly tiled utility wall |
| Photos | Complete |
| Video | Yes |
| Confidence | Confirmed |
The route should be recorded as: Candidate electrical route — technical assessment required
rather than: Electrical route approved.
A survey should finish with evidence, not premature approval.
Comparing Candidate Electrical Routes
Where more than one route is possible, record them separately. For example:
| Factor | ELEC-ROUTE-01 | ELEC-ROUTE-02 |
|---|---|---|
| Approximate length | 9m | 15m |
| Internal disruption | Low | Medium |
| External exposure | Short | Longer |
| Penetrations | 1 | 2 |
| Customer preference | Preferred | Backup option |
| Access difficulty | Straightforward | Loft access required |
| Nearby equipment review | Minimal | Required |
The survey does not choose the final route. It creates comparable evidence for the design.
KEY TAKEAWAY
The survey collects comparable evidence. The design chooses the route.
When Further Investigation Is Required
Some electrical routes cannot be fully confirmed from the first survey. Further investigation may be required where the consumer-unit capacity is uncertain, existing major loads are not fully known, the internal route depends on uncertain construction, the external route cannot be confirmed, an accessible exit point cannot be identified, nearby electrical equipment requires product-specific review, or customer constraints significantly limit the available options.
Possible survey statuses include: Ready for electrical assessment, Additional survey information required, Consumer-unit review required, Route clarification required, Alternative route should be considered.
This keeps uncertainty visible rather than forcing a premature decision.
Common Electrical-Route Survey Mistakes
Photographing Only the Consumer Unit
Problem: A photo of the consumer unit does not show how the cable could reach the outdoor unit.
Better: Survey the whole route between the two.
Treating a Spare Way as Confirmed Capacity
Problem: A spare way in the consumer unit does not confirm electrical suitability.
Better: Record it as evidence and leave assessment to the electrician.
Ignoring Existing Major Loads
Problem: EV chargers, solar PV and other equipment affect available capacity.
Better: Record what is already installed.
Assuming the Shortest Line Is the Real Route
Problem: A straight line on a plan may not reflect what is actually achievable.
Better: Trace the practical route through walls, floors and voids.
Missing Difficult Sections
Problem: Tiled walls, fitted kitchens and finished rooms can significantly complicate installation.
Better: Record these obstacles clearly.
Not Recording the Exit Point Properly
Problem: The transition from inside to outside is often the most complex part of the route.
Better: Record construction, access and surrounding features at this point.
Ignoring External Obstacles
Problem: Rainwater pipes, cladding and other services can affect the external route.
Better: Record what the cable would need to pass.
Not Measuring Route Length
Problem: Without approximate distances, later cable-sizing assessment becomes guesswork.
Better: Record realistic section lengths, including vertical rises.
Choosing the Isolator Position During the Survey
Problem: Final isolator location depends on the product and electrical design.
Better: Record a practical area and leave the final decision to design.
Ignoring Customer Preferences
Problem: A technically possible route can still be unacceptable to the household.
Better: Record known constraints during the survey.
Asking a Homeowner to Investigate Electrical Equipment
Problem: This creates unnecessary risk.
Better: Limit remote survey requests to safe, visible evidence.
An electrical-route survey should describe a path, not just two endpoints.
Electrical-Route Completeness Check
Before completing the survey, confirm: candidate route referenced, consumer-unit area recorded, spare way noted as evidence only, existing major loads recorded, internal route traced, internal obstacles recorded, exit point recorded, external route traced, approximate route length recorded, penetrations recorded, proposed isolator area recorded, nearby external electrical equipment recorded, customer constraints recorded, photos complete, video taken where useful, confidence recorded, and critical unknowns flagged.
The survey can then be marked: Ready for electrical assessment, or Further information required.
What Happens After the Electrical-Route Survey?
The survey provides the site evidence needed for the electrical design. The process may then look like this:
Candidate route surveyed → Existing supply and loads assessed → Required heat-pump electrical demand established → Consumer-unit suitability assessed → Cable route confirmed → Cable size and protection determined → Isolator location confirmed → Product-specific siting requirements checked → Installation carried out by the appropriate competent person
KEY TAKEAWAY
The survey establishes the route. The electrical design determines what that route needs to carry.
Frequently Asked Questions
Record the consumer-unit area, existing major loads, a practical internal route to a building exit point, the external route to the proposed outdoor unit, approximate length, obstacles, a possible isolator area, nearby electrical equipment, customer constraints, photos and any uncertainty.
A spare way can be useful evidence, but it does not confirm electrical suitability. The final assessment should consider the existing installation, protection and available capacity.
This depends on factors including existing loads, supply capacity and the heat pump’s electrical requirements. The survey should record the relevant evidence so the assessment can be carried out by the appropriate competent person.
It can, along with other significant existing loads. Record what is already connected so the full picture is available during assessment.
There is no fixed universal distance. Cable length is one of several factors considered during electrical design, alongside cable type, protection and voltage drop. The survey should record the approximate route length rather than assuming a limit.
Record the practical path from the consumer unit toward the building exit, including likely obstacles such as tiled walls, fitted kitchens, solid floors or finished ceilings.
This depends on the property and the outdoor-unit location. The survey should record a practical exit point along with wall construction and surrounding features.
A suitable area should be identified during the survey, but the final decision belongs to the electrical and product-specific design.
Yes. Nearby electrical equipment can become relevant once a specific heat-pump product is selected.
A homeowner can usually provide photographs of the closed consumer unit, the meter and the general property layout, along with video showing a possible cable route. They should not be asked to remove covers, touch electrical equipment or investigate anything unsafe.
No. This is a survey intended to collect site evidence. It does not replace the electrical design, inspection or certification carried out by the appropriate competent person.
Where realistic alternatives exist, yes. Comparing routes can help identify the most practical option in terms of length, disruption and access.
Record it as an obstacle. This information helps avoid unexpected disruption or cost once installation begins.
Record it as uncertain rather than assuming a particular construction or route. Further investigation can be identified where necessary.
Yes, where safely visible. It can provide useful context alongside the consumer-unit information.
Yes. A technically possible route may still be unacceptable to the household, for example where it would cross a recently decorated or tiled area.
Yes. Video can be particularly useful for showing how the internal and external sections of the route connect together.
The recorded evidence supports assessment of the existing supply, loads and cable route, followed by electrical design covering cable size, protection and installation. That work should be completed by the appropriate competent person.
Survey the Whole Route, Not Just the Two Ends
A useful electrical-route survey should record the consumer-unit area, existing major loads, the internal route, the exit point, the external route, approximate length, obstacles, a possible isolator area, nearby electrical equipment, customer constraints, photos and any uncertainty.
Do not survey only the consumer unit and the heat pump. Survey the route between them.
A spare way is useful survey information, not electrical approval.
The survey records the route. The electrician designs the circuit.
HEAT PUMP DESIGN SUPPORT
Send us the completed electrical-route survey alongside the wider project and we’ll factor it into the design.
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