SmartHeat · Project

Salt-Based Thermal Battery That Cuts Household Heating Bills by 75%

energyPilotedTRL 7

Imagine a fridge-sized battery that stores heat instead of electricity — using salt dissolved in mineral oil. You charge it up when power is cheap or the sun is shining, then it releases warmth for up to 25 hours, keeping your home heated through the night or on cloudy days. Paired with a heat pump and solar panels, it acts like a smart buffer that decides when to store and when to release, slashing heating costs dramatically compared to oil boilers. A cloud-based control system manages everything in real time, so the homeowner doesn't have to think about it.

By the numbers

25 kWh

Thermal storage capacity of the compact battery

25 hours

Heat displacement duration

75%

Heating bill reduction compared to oil burner

40%

Efficiency increase versus stand-alone heat pump

€34.5 billion

Target market value

€83 million

Expected cumulated turnover 5 years after project completion

€1,110,130

EU contribution to the project

The business problem

What needed solving

Household heating accounts for a massive share of residential energy costs and carbon emissions across Europe. Most homes still rely on oil boilers or stand-alone heat pumps that waste energy during peak demand and cannot store surplus solar or cheap off-peak electricity. Homeowners and housing providers need a compact, affordable way to store thermal energy and release it on demand — cutting bills and carbon at the same time.

The solution

What was built

SUNTHERM built a 25 kWh compact thermal battery based on salt hydrate dissolved in mineral oil (patent pending), measuring 60 × 60 × 200 cm. The system integrates with solar thermal collectors and a smart grid-enabled heat pump, managed by a cloud-based real-time control unit. Physical prototypes were delivered and tested in field demonstrations.

Audience

Who needs this

HVAC manufacturers looking to add thermal storage to their product linesProperty developers building zero-carbon residential projectsDistrict heating utilities seeking peak load shaving solutionsEnergy service companies (ESCOs) offering heating-as-a-serviceHousing associations retrofitting older buildings for energy efficiency

Business applications

Who can put this to work

District heating and energy utilities

mid-size

Target: Heating utility or district energy provider

If you are a district heating provider dealing with peak load management and rising fuel costs — this project developed a 25 kWh thermal storage battery with cloud-based real-time control that enables peak load shaving and load balancing. The system stores excess energy during low-demand periods and releases it during peaks, reducing grid stress and cutting end-user heating bills by up to 75% compared to oil burners.

Residential construction and property development

any

Target: Property developer or housing association

If you are a property developer looking to offer zero-carbon heating in new residential builds — this project built a compact thermal battery (60 × 60 × 200 cm) that integrates with solar thermal collectors and heat pumps. It delivers twice the hot water of a conventional tank while fitting in a standard utility room, and provides a 40% efficiency gain over a stand-alone heat pump.

HVAC and heating equipment manufacturing

mid-size

Target: Heat pump or boiler manufacturer

If you are an HVAC manufacturer seeking to expand your product line with smart storage solutions — this project developed a patented salt hydrate thermal battery with 25 kWh capacity and 25 hours of heat displacement. The technology integrates with existing heat pumps and solar thermal systems, targeting a market worth €34.5 billion according to the project's own assessment.

Frequently asked

Quick answers

What does the system cost and what are the savings?

The project does not disclose unit pricing. However, the objective states homeowners can reduce heating bills by 75% compared to oil burners. The system achieves a 40% efficiency increase versus a stand-alone heat pump, which would translate into significant annual energy cost savings.

Can this scale to apartment buildings or commercial properties?

The current design targets household-scale heating with a 25 kWh thermal battery measuring 60 × 60 × 200 cm. Based on available project data, scaling to larger buildings would likely require multiple units or a redesigned system. The cloud-based management platform could potentially coordinate multiple batteries.

What is the IP situation — can I license this technology?

SUNTHERM holds a patent pending on the salt hydrate thermal storage battery. As a single-partner SME project, all IP sits with SUNTHERM APS in Denmark. Licensing or OEM agreements would need to be negotiated directly with them.

Has this been tested in real homes?

Yes. The project delivered prototypes specifically for field tests and demonstrations, as documented in two separate deliverables. The SME-2 funding scheme requires demonstration-level validation, confirming real-world testing took place.

How does it connect to existing heating systems?

SmartHeat is designed as an integrated system coupling the thermal battery with solar thermal collectors and a smart grid-enabled heat pump. The cloud-based online control unit manages heat flows in real time. Based on available project data, it supports radiators, floor heating, and hot water delivery.

What happens after the EU funding ended?

The project closed in February 2021 with an expected cumulated turnover target of €83 million within 5 years after completion. SUNTHERM APS had a project website at smartheat.dk. Current commercial status would need to be verified directly with the company.

Is this compliant with EU energy regulations?

The system targets zero-carbon household heating using solar thermal and smart grid integration, aligning with EU decarbonization goals. The project was funded under the SME Instrument for resource-efficient eco-innovative food production and processing. Based on available project data, specific regulatory certifications are not detailed in the objectives.

Consortium

Who built it

This is a single-company project: SUNTHERM APS, a Danish SME that is both the sole partner and coordinator. With 100% industry participation and no university or research institute involvement, the project was entirely commercially driven — the company used EU SME Instrument Phase 2 funding (€1,110,130) to advance its own product toward market. For a potential business partner, this means all decision-making authority and IP sit with one entity, making negotiations straightforward. The absence of academic partners suggests the core R&D was already done before EU funding, and the grant focused on scaling, testing, and market preparation.

SUNTHERM APSCoordinator · DK

How to reach the team

SUNTHERM APS is a Danish SME — contact details can be found via their website or Danish business registry (CVR)

Order a report on this consortium See SUNTHERM APS profile →

Next steps

Talk to the team behind this work.

Want an introduction to the SmartHeat team? SciTransfer can connect you with the right person at SUNTHERM and provide a detailed technology brief.

Order a report on this topic More in Energy & Climate