Published： July 8, 2026
Last Modified：August 27, 2026
PVT and ground-source heat pumps (GSHPs) are generally complementary technologies, not direct alternatives.
A PVT collector converts solar radiation into:
A ground-source heat pump extracts heat from the ground and upgrades it to a useful temperature for:
A properly designed PVT-GSHP system can combine the two:
┌──→ Electricity
│
Solar → PVT ─────────┤
│
└──→ Thermal Energy
↓
Ground / HX
↓
Heat Pump
↓
Building LoadThe important engineering opportunity is therefore not simply PVT versus GSHP.
It is:
How can PVT improve the thermal and electrical performance of a ground-source heat-pump system?
The reviewed PVT-SAHP literature identifies two major benefits of coupling PVT with ground-source heat pumps:
A further benefit is particularly important for engineering design:
PVT can help regenerate the ground heat exchanger and reduce long-term source degradation.
A GSHP extracts heat from the ground through a ground heat exchanger.
A simplified heating system is:
Ground
↓
Ground Heat Exchanger
↓
Heat Pump Evaporator
↓
Compressor
↓
Condenser
↓
BuildingThe ground provides a relatively stable thermal source compared with outdoor air.
However, a ground-source system is not an unlimited heat reservoir.
If heat is continuously extracted from a borehole field without sufficient thermal recovery, the surrounding ground temperature can decline.
That can reduce the source temperature available to the heat pump.
The result can be:
Long-term heat extraction
↓
Ground temperature decline
↓
Lower source temperature
↓
Higher temperature lift
↓
Potentially lower COPThis is where PVT can provide an additional function.
PVT introduces a solar thermal source in addition to the PV electrical output.
┌──→ Electricity
Solar radiation → PVT
└──→ HeatThe thermal output can be used in different ways.
For a GSHP application, one particularly important pathway is:
PVT
↓
Thermal circuit
↓
Ground heat exchanger
↓
GroundThe ground can therefore act as a form of seasonal thermal storage.
The PVT system can inject solar heat into the ground when solar energy is available.
This is commonly described as ground-loop or borehole regeneration.
There are three important reasons.
PVT can provide heat at a temperature potentially higher than the undisturbed ground temperature.
This can raise the effective evaporating/source temperature.
Extracting heat from the PVT collector can reduce PV-cell temperature.
Because PV electrical efficiency decreases with increasing cell temperature, thermal extraction can improve electrical operating conditions.
The review identifies this PV cooling effect as one of the two principal benefits of PVT-GSHP coupling.
Solar heat can be transferred into the ground during periods when solar energy is available.
This can compensate for some of the heat extracted from the borehole during heating operation.
The objective is to reduce long-term heat-source degradation.
| Function | PVT | Ground-source heat pump |
|---|---|---|
| Solar electricity | Yes | No |
| Solar thermal collection | Yes | No |
| Ground heat extraction | No | Yes |
| Heat-temperature upgrading | No | Yes |
| PV-cell cooling | Yes | No |
| Borehole regeneration | Can provide it | Receives regenerated heat |
| Building heating | Indirectly | Yes |
| DHW production | Through system integration | Yes |
| Cooling | Through suitable integrated system | Yes |
| Seasonal thermal storage | Can support it | Ground can provide it |
This is why the comparison should not be framed as:
Which one replaces the other?
Instead:
What system architecture provides the best combination of solar collection, ground-source stability and heat-pump performance?
A simplified integrated system is:
┌──────────────→ Electricity
│
Solar → PVT ─────┤
│
└→ Thermal Loop
↓
Ground Heat Exchanger
↓
Ground
↓
Heat Pump Source
↓
Heat Pump
↓
Building LoadThe exact hydraulic and thermal arrangement depends on whether PVT and the ground loop operate:
This distinction matters.
In a parallel configuration, PVT and the ground source can provide heat to the heat-pump system through separate source paths.
Conceptually:
┌──→ PVT
│
Heat Pump ──────┤
│
└──→ GroundThe system can select or combine the sources according to operating conditions.
This architecture provides source flexibility.
The literature review reports that glazed PVT operated in parallel with a ground-source heat pump was identified by IEA SHC & Heat Pump Programme Task 44/Annex 38 as the best configuration from an SPF perspective.
That is a literature-based conclusion under the referenced study framework—not a universal rule for every project.
A series arrangement can place PVT and the ground source sequentially in the thermal pathway.
A simplified concept is:
PVT
↓
Thermal circuit
↓
Ground / Borehole
↓
Heat Pumpor, depending on system topology:
PVT
↓
Ground-loop regeneration
↓
Ground-source HPThe key objective is often ground regeneration.
The source review specifically reports that:
Series configuration is preferable when a shorter borehole heat exchanger and ground regeneration are required.
Therefore:
| Objective | Configuration identified in source |
|---|---|
| Favorable SPF | Parallel glazed PVT |
| Shorter borehole + regeneration | Series PVT + ground |
Again, this should be interpreted as the reported Task 44/Annex 38 finding rather than an absolute design rule.
A borehole heat exchanger extracts or rejects heat from the surrounding ground.
For a heating-dominated building:
Winter
Ground
↓
Heat extracted
↓
Heat Pump
↓
BuildingOver many years, continuous extraction can lower the average ground temperature.
PVT can reverse part of this process:
Summer / Solar availability
PVT
↓
Solar thermal energy
↓
Ground loop
↓
Borehole
↓
Ground temperature recoveryThis is thermal regeneration.
The objective is not simply to add heat.
The objective is to improve the long-term thermal balance of the ground heat exchanger.
Consider a high-density borehole field.
Multiple heat pumps continuously extract heat:
HP 1 ──→ Ground
HP 2 ──→ Ground
HP 3 ──→ Ground
HP 4 ──→ Ground
↓
Long-term heat extraction
↓
Ground temperature declineIf the ground does not recover sufficiently:
Source temperature ↓
↓
Evaporation temperature ↓
↓
Temperature lift ↑
↓
Compressor work ↑
↓
COP ↓PVT can introduce additional solar heat into the ground:
Solar
↓
PVT
↓
Ground regeneration
↓
Ground temperature recoveryThe review identifies this as particularly important where borehole heat-exchanger density is high and long-term heat extraction can degrade the source.
One of the strongest reasons to integrate PVT and GSHP is that the PVT thermal output can produce two different system-level benefits.
Heat extraction:
PVT temperature ↓
↓
PV electrical efficiency can improveSolar heat injection:
Ground temperature ↑
↓
Heat-pump source condition can improveTherefore:
PVT
/ \
↓ ↓
PV cooling Ground regeneration
↓ ↓
Electricity Better source condition
↓
GSHPThis is more than simple solar-assisted heating.
It is thermal and electrical system integration.
The review specifically identifies PVT + ground-source systems as particularly relevant in northern and colder countries.
The reason is straightforward.
Air-source heat pumps experience lower source temperatures during cold weather.
Ground-source systems can provide a more stable source.
The source review notes that ground-source systems can be more cost-effective than air-based technologies in colder countries, where air-source performance can deteriorate at low ambient temperatures.
Adding PVT can then provide:
This makes the architecture particularly interesting for heating-dominated applications.
This is an important distinction.
PVT should not automatically be treated as a replacement for the borehole field.
Instead, PVT can become part of the source-management strategy.
The complete system may be:
PVT
↓
Solar thermal contribution
+
Ground loop
↓
Heat Pumprather than:
PVT
↓
No ground loop requiredWhether PVT can materially reduce borehole requirements depends on:
Project-specific modelling is therefore required.
Suppose the heat pump needs:
Qsource=Qload−WcompressorQ_{source}=Q_{load}-W_{compressor}
If part of the source energy can be supplied by PVT, the ground does not necessarily have to provide all of the evaporator-side heat.
Conceptually:
Total HP source demand
│
├── PVT contribution
│
└── Ground contributionTherefore:
PVT can reduce the amount of heat that must be extracted from the ground during appropriate operating periods.
This can be particularly valuable in a heating-dominated system.
However, the actual reduction must be calculated from the annual energy balance rather than assumed.
The value of PVT regeneration becomes clearer when viewed seasonally.
Building heating demand ↑
↓
GSHP extracts heat
↓
Ground loses heatSolar availability ↑
↓
PVT thermal output ↑
↓
Ground can receive heatThe annual objective becomes:
Annual heat extracted
≈
Annual heat regeneratedThe exact balance does not necessarily need to be zero for every system, but the design should prevent unacceptable long-term source degradation.
Regeneration can also allow the PVT collector to operate at relatively low temperature.
This matters because lower PVT operating temperatures generally reduce thermal losses and can support favorable PV operating conditions.
The source material identifies ground-heat-exchanger regeneration as potentially allowing the lowest PVT collector temperatures among the described heat-pump integration approaches.
This creates an attractive chain:
Low-temperature PVT operation
↓
Good heat rejection to ground
↓
Ground regeneration
+
Potentially favorable PV temperatureThis comparison is useful for project screening.
| Factor | PVT + GSHP | PVT + Air-Source HP |
|---|---|---|
| Secondary source | Ground | Ambient air |
| Borehole required | Yes | No |
| Ground regeneration possible | Yes | No |
| Cold-weather source stability | Generally strong | Ambient-dependent |
| Installation complexity | Higher | Lower |
| Upfront ground infrastructure | Higher | Lower |
| PVT thermal integration | Yes | Yes |
| Suitable cold-climate application | Strong candidate | Requires careful evaluation |
| Retrofit simplicity | Lower | Generally higher |
The review identifies air-source integration as a more flexible and cost-effective secondary-source choice in hot/temperate climates and retrofit applications, while ground-source coupling is specifically relevant to colder countries.
The comparison should not simply be:
PVT system = more efficient.
A more useful comparison is:
| System | Electricity | Solar heat | Ground source | Ground regeneration |
|---|---|---|---|---|
| Conventional GSHP | No direct solar generation | No | Yes | No |
| PV + GSHP | Yes | No | Yes | No |
| PVT + GSHP | Yes | Yes | Yes | Potentially yes |
The third architecture has additional integration possibilities.
But it also has additional components and controls.
No.
The benefit depends on how the systems are designed and operated.
Potential benefits include:
Potential challenges include:
Therefore:
PVT should be evaluated as part of the whole GSHP system, not as an automatically beneficial add-on.
The collector configuration affects the integration.
Advantages include:
Advantages include:
The review reports that covered PVT can increase water temperature and heat gain, enabling higher evaporation temperature and potentially benefiting overall COP, while uncovered PVT generally offers stronger electrical performance.
For ground regeneration, however, extremely high collector temperature is not necessarily the objective.
The required operating condition must be determined from the ground-loop and system design.
The Solis Engineering Design Series uses Brine 450W as its primary indirect-expansion PVT reference architecture.
A GSHP integration can be represented as:
┌──→ Electricity
│
Solar → Brine 450W PVT
│
↓
Brine Thermal Loop
│
┌────────┴────────┐
↓ ↓
Ground Regeneration Heat Exchanger
│ │
↓ ↓
Ground HP Evaporator
│
↓
Heat Pump
│
↓
BuildingThe actual project architecture should determine whether the PVT thermal circuit:
The indirect architecture separates the solar thermal circuit from the heat-pump refrigerant circuit.
That means:
PVT side
Brine / water-glycol
│
↓
Heat exchanger
│
↓
Heat-pump refrigerantThis separation allows independent selection of the thermal-fluid circuit and the heat-pump refrigerant.
The source review identifies this as one of the principal benefits of IDX architecture.
For a PVT + ground-source system, this can be useful because the designer must coordinate:
The DX 450W reference design is fundamentally different.
In DX PVT:
PVT
↓
Refrigerant evaporation
↓
Compressor
↓
CondenserThe PVT collector itself is part of the refrigerant-side evaporator.
The reviewed literature states that direct integration of a borehole heat exchanger with DX-PVT-SAHP is generally not performed as a simultaneous parallel arrangement; the identified example used the borehole exchanger in series on the user side.
Therefore, for PVT + GSHP design:
Brine/IDX is the more natural Solis reference architecture for discussing PVT–ground-loop integration.
DX remains a valid reference architecture for direct PVT heat-pump systems, but should not be presented as though its ground-source topology is identical to the brine system.
A conceptual Solis reference architecture is:
SOLAR
↓
Brine PVT 450W
↓
Brine Loop
↙ ↘
↓ ↓
Heat Pump HX Ground Loop
↓ ↓
└──────┬────┘
↓
HP Evaporator
↓
Compressor
↓
Condenser
↓
Building LoadThe controls determine whether PVT heat is:
This is the type of system architecture that should be evaluated through annual simulation and thermal-balance analysis.
A conceptual control sequence can be:
PVT → Heat PumpUse available PVT heat directly when the source conditions are favorable.
PVT → GroundUse excess thermal energy for ground regeneration where appropriate.
Ground → Heat PumpThe GSHP operates from the ground source.
PVT → GroundRegenerate the borehole field.
This is only a conceptual control framework.
Actual switching temperatures, flow rates and control logic require system modelling.
Ground regeneration provides seasonal thermal storage, but it does not eliminate the need to evaluate short-term storage.
For example:
Solar radiation
↓
PVT
↓
Thermal output
↓
┌───┴────┐
↓ ↓
HP StorageThe source material emphasizes the importance of properly sized thermal storage and identifies storage selection as a key system-design decision.
The correct storage strategy depends on:
This is an important misconception.
A borehole field has finite thermal capacity and finite heat-transfer characteristics.
Therefore:
Adding more PVT does not automatically mean more useful regeneration.
If PVT is oversized:
PVT area ↑
↓
Excess thermal output
↓
Ground temperature ↑
↓
Possible operating constraintsThe system must be sized around the complete annual energy balance.
The source material explicitly warns against oversizing PVT systems, particularly where heating demand is concentrated in winter while solar availability is low.
The review provides a specific general sizing principle:
PVT area should be defined to cover the thermal load in the month with the highest solar radiation, avoiding hot-water overproduction.
At the same time:
Heat-pump size should be based on the building peak thermal load without relying on the PVT contribution, so that the system can operate when solar availability is scarce.
These are general design heuristics from the reviewed paper, not project-specific sizing rules.
A real GSHP/PVT project requires:
A proper PVT-GSHP comparison should evaluate at least:
A GSHP/PVT system operates throughout changing seasons.
Therefore, a single operating-point COP is insufficient.
The source defines Seasonal Performance Factor (SPF) as an integrated seasonal/annual performance metric analogous to COP but calculated over a season or year.
This is particularly important for PVT-GSHP systems because:
Therefore:
Annual or seasonal performance is more meaningful than one favorable operating point.
PVT and GSHP perform different functions.
A GSHP system must be evaluated over time, not just at initial conditions.
Ground regeneration may be the better destination under some operating conditions.
More collector area does not automatically produce better annual performance.
Seasonal performance and ground temperature evolution matter.
Their source-side architectures are fundamentally different.
The actual reduction in borehole requirements must be demonstrated through thermal-balance modelling.
PVT + GSHP deserves serious evaluation when several of the following conditions apply:
The combination is particularly interesting for heating-dominated systems in colder climates.
It may be less attractive when:
The review itself identifies the lack of comprehensive economic analysis as a limitation in the available literature.
Therefore, technical performance alone should not be treated as a complete investment decision.
Does the project need heating?
│
Yes
↓
Is GSHP technically/economically suitable?
│
┌───┴───┐
No Yes
↓ ↓
Other HP Is solar electricity + heat
valuable?
│
┌────┴────┐
No Yes
↓ ↓
GSHP Evaluate PVT + GSHP
│
↓
Is ground regeneration
valuable?
│
┌────┴────┐
No Yes
↓ ↓
Parallel / Series or
direct source regeneration
integration architectureThe final architecture should be selected from the annual system analysis.
The strongest case for the technology combination is not simply:
“PVT makes GSHP more efficient.”
It is a more complete proposition:
PVT can simultaneously generate electricity, provide a solar thermal source, cool the PV cells, support the heat pump, reduce ground heat extraction under suitable conditions, and regenerate the ground heat exchanger.
That makes PVT-GSHP particularly interesting as an integrated energy system.
In most cases, the answer is:
Do not treat them as mutually exclusive technologies.
A conventional GSHP provides a stable low-temperature heat source.
PVT adds:
The most important engineering distinction is therefore between:
Ground → Heat Pump → BuildingPV → Electricity → Heat Pump
Ground → Heat Pump → Building ┌→ Electricity
│
Solar → PVT ────────┤
│
└→ Thermal Energy
↓
┌─────────┴─────────┐
↓ ↓
Heat Pump Ground Loop
↓ ↑
└──── Building RegenerationThe third architecture provides the greatest integration potential—but also requires more careful design.
The literature identifies parallel glazed PVT + GSHP as favorable from an SPF perspective, while series PVT + ground is preferable when shorter boreholes and ground regeneration are key objectives.
These findings should be treated as engineering guidance from the cited literature, not universal rules.
They are generally not direct substitutes. PVT collects solar electricity and heat, while a GSHP upgrades heat from a ground source.
Yes. PVT can provide thermal energy to the heat-pump system and can also regenerate the ground heat exchanger.
Potentially, but this cannot be assumed. The actual effect depends on annual heating demand, PVT area, solar resource, ground conditions and system control.
Ground regeneration is the process of returning thermal energy to the ground heat exchanger to compensate for some of the heat extracted during heating operation.
Continuous heat extraction can lower the average ground temperature around a borehole field. Regeneration can help mitigate this long-term source degradation.
It can. PVT may provide a higher-temperature source and can therefore reduce the temperature lift required by the heat pump under suitable operating conditions. The actual improvement must be calculated for the specific system.
It can be particularly relevant in cold, heating-dominated climates, where ground-source systems can have advantages over air-source systems and PVT can provide both solar heat and ground regeneration.
The reviewed IEA Task 44/Annex 38 findings reported parallel glazed PVT as favorable from an SPF perspective, while series configuration was preferable when shorter boreholes and ground regeneration were the objectives.
Yes, this is one of the principal concepts discussed in the literature. Solar thermal energy can be injected into the ground during periods of solar availability.
For the Solis reference-design framework, Brine 450W is the more natural reference architecture for PVT-ground-loop integration because the PVT thermal circuit is separated from the refrigerant circuit. DX PVT should be treated as a different architecture rather than simply substituted into the same topology.
No. PVT-assisted regeneration is a method of managing the ground thermal balance; it does not automatically eliminate the need for a ground heat exchanger.
Alessandro Miglioli, Niccolò Aste, Claudio Del Pero, Fabrizio Leonforte
Photovoltaic-thermal solar-assisted heat pump systems for building applications: Integration and design methods
Energy and Built Environment, Volume 4, 2023, pp. 39–56.
The paper specifically reviews:
The source identifies PVT-ground coupling as an important configuration for improving PV electrical performance, heat-pump source conditions and ground thermal balance.
The PVT application literature identifies the PVT + heat-pump system and ground-heat-exchanger regeneration as a major system architecture, including regeneration as a way of achieving low PVT collector operating temperatures.
The literature supports:
It does not establish:
Those require project-specific calculations and applicable product evidence.
The Brine 450W and DX 450W configurations are therefore used here as Solis Reference Designs, not as unsupported performance claims.
→ P5 · PVT Comparison Guide
→ P5-I01 · PVT vs PV
→ P5-I02 · PVT vs Solar Thermal
→ P5-I03 · PVT vs Heat Pump
→ P5-I05 · PVT vs Air-Source Heat Pumps
→ P5-I06 · DX PVT vs Brine PVT
→ P3 · PVT System Design & Integration
→ Brine PVT Heat Pump System Design
→ PVT Ground-Loop Regeneration Design
Start with the complete energy balance:
building load → PVT output → heat-pump source → ground extraction → ground regeneration → seasonal balance → controls.
Do not size the PVT array or borehole independently.
Design the complete system.
Explore the Solis PVT Engineering Design Series for engineering guidance based on Brine 450W and DX 450W reference architectures.