Sonntag

What Sonntag does

Sonntag (legal entity: Heizungsbau Sonntag GmbH & Co. KG) is a German family-owned trades company that designs, installs, and services residential bathroom renovations and modern heating systems for homeowners across the Grafschaft, Ahrtal, and Rhein-Sieg regions of Rhineland-Palatinate and North Rhine-Westphalia. The company was founded in 1950 in Esch as a blacksmith and locksmith workshop, was converted into Heizungsbau Sonntag GmbH in 1988, and relocated to its current headquarters at Robert-Koch-Straße 6, Grafschaft-Gelsdorf in 2008; in 2026 it restructured into a GmbH & Co. KG and acquired Bad und Fliesen Gruber GmbH. Its service offering spans the full residential bathroom lifecycle (design, renovation across Basic, Barrier-Free, and Luxury tiers, and an in-house showroom) alongside the full range of modern heating technologies, including air- and ground-source heat pumps, gas condensing boilers, photovoltaic with battery storage, solar thermal, wood/pellet systems, fuel-cell combined heat and power units (e.g., Viessmann Vitovalor), and hydraulic balancing, supported by full-service and partial-service maintenance contracts and a daily emergency service for contract customers.

The company's underlying technology consists of branded mechanical and hydronic systems sourced through partnerships with Viessmann, Stiebel Eltron, Geberit, Duravit, Kaldewei, Hansgrohe, Villeroy & Boch, Keuco, HSK, and Zehnder, integrated and commissioned by in-house Anlagenmechaniker SHK technicians. Sonntag differentiates itself through single-source project delivery, coordinating all trades (tiling, electrical, drywall, painting, carpentry) as a single contractor under in-house project coordination. Customer acquisition runs through the company website, an Instagram and Facebook presence, a WhatsApp service line, a physical showroom, a published online price list, and direct field service dispatched by an in-house Disposition team.

The business model is primarily transaction- and contract-based services revenue. One-time installation projects (bathroom renovation, heat pump, PV, fuel cell, condensing boiler) are quoted as fixed-price engagements that bundle labor, branded equipment, and trade coordination. Recurring maintenance and repair services generate professional-services revenue on pay-as-you-go terms, with role-based hourly rates (€57–€84/hour ex VAT for technicians and master craftsmen), seven-zone travel fees (€25.40–€131.60), and emergency surcharges of €100 for non-contract customers and €50 for partial-contract customers. Hardware and spare parts are bundled into project pricing rather than sold standalone. Primary customers are residential homeowners in single-family and multi-family homes; commercial customers form a secondary segment. Pricing is publicly disclosed, distinguishing Sonntag from typical opaque regional trades competitors.

Name

Sonntag

Legal name

Heizungsbau Sonntag GmbH & Co. KG

Website

https://sonntag-grafschaft.de

Company type

Private

Founded year

1950

Operating status

Operating

Headcount range

11–50 employees

Short description

Sonntag is a German family-owned trades company (est. 1950) that designs, renovates, and services residential bathrooms and modern heating systems — including heat pumps, PV, fuel cells, and condensing boilers — for homeowners across the Grafschaft, Ahrtal, and Bonn regions.

Ownership category

akta.pro rank

Product category

Residential Heating and Bathroom Installation Services

NAICS

Home and Garden Equipment Repair and Maintenance (811411)

SIC

Steam & Air-Conditioning Supply (4961)

akta.pro primary industry

Residential HVAC System Installation (Furnace/AC/Heat Pump) (HSAOAGAA)

akta.pro secondary industry

New Construction HVAC Rough-In & Final Set (Residential/Light Commercial) (HSAOAGAL)

Keywords

• Bathroom renovation services
• Heating system installation
• Heat pump installation
• Condensing boiler service
• Photovoltaic system installation

Headquarters

HQ city

Ahrweiler

HQ country

Germany

HQ region

Europe

Offices2 records

Markets served

GTM type

B2C

Offering type

Services

Cost components

Personnel, Operations, Supply Chain, Marketing or Sales, Infrastructure

Revenue model

1. Installation and Construction Services: Installation of heating systems (heat pumps, condensing boilers, solar thermal, PV, fuel cells) and bathroom/bad installations including complete renovations. Revenue is generated through project-based contracts, typically quoted as fixed prices per service.
2. Maintenance and Repair Services: Ongoing maintenance contracts (Vollservice and Teilservice) and repair services. Customers pay for service hours and travel zones. Emergency/after-hours service available for contract and non-contract customers at premium rates.
3. Spare Parts and Materials Supply: Supply of branded heating and sanitary components as part of installation and maintenance services, bundled into project pricing.

Pricing tiers

Go-to-market motion1 record

Distribution channels3 records

Marketing channels8 records

Core offering

Sonntag is a traditional German heating and bathroom installation contractor that delivers complete bathroom renovations and modern heating system installations (heat pumps, condensing boilers, photovoltaic, solar thermal, fuel cells, wood/pellet systems) for residential customers in the Grafschaft, Ahrtal, and Bonn region. The company acts as a single-source coordinator across all trades, providing design consultation, installation, hydraulic balancing, and ongoing maintenance under one contract.

Product overview

Sonntag (Heizungsbau Sonntag GmbH & Co. KG) is a traditional crafts and trades company offering integrated bathroom design/renovation and heating technology services for residential customers in the Grafschaft, Ahrtal, and Bonn regions. The company operates as a single integrated service provider rather than a software platform. Its bathroom division covers design consultation, renovation execution, and a physical showroom across three tiers (Basic, Barrier-Free, Luxury). Its heating division spans all major heating technologies including heat pumps, condensing boilers, pellet/wood systems, fuel cells, solar thermal, and photovoltaic installations, plus hydraulic balancing and maintenance services. The company coordinates all related trades (tiling, painting, electrical) as a single contractor, covering the full project lifecycle from planning through commissioning.

Differentiator

Problem solved

Functional benefit

Products and services

• Badgestaltung (Bathroom Design) Full-service bathroom design for residential customers, including consultation, layout planning, material selection, and full craft execution across three tiers (Basic, Barrier-Free, Luxury).
• Badsanierung (Bathroom Renovation) Complete bathroom renovation delivered from a single contractor, covering demolition, installation, and finishing for all trades, with tiered packages (Basic, Barrier-Free, Luxury).
• Wärmepumpen (Heat Pump Installation) Installation and maintenance of air-source and ground-source heat pump systems for residential heating, including sizing, hydraulic integration, commissioning, and long-term servicing.
• Photovoltaikanlagen (PV System Installation) Design, supply, and installation of rooftop photovoltaic systems including panel layout, inverter sizing, battery storage integration, and grid registration.
• Brennwerttechnik (Condensing Boiler Installation) Installation, replacement, and maintenance of gas condensing boilers, including old unit disposal, chimney adaptation, and system commissioning.
• Holz/Pellets (Wood and Pellet Heating Installation) Supply and installation of pellet boilers, log wood boilers, and combination units, including pellet storage, hydraulics, and control system setup.
• Solarthermie (Solar Thermal Installation) Installation of solar thermal systems for domestic hot water preheating and space heating support, compliant with EEWärmeG renewable energy obligations.
• Brennstoffzellenheizung (Fuel Cell Heating Installation) Installation of combined heat and power fuel cell units (e.g., Viessmann Vitovalor) that simultaneously generate electricity and heat for residential homes.
• Hydraulischer Abgleich (Hydraulic Balancing) Measurement and adjustment of heating system water distribution to ensure even heat delivery across all radiators, reducing energy consumption and operating costs.
• Kundendienst & Wartung (Service and Maintenance Contracts) Preventive maintenance, inspection, and emergency repair services for heating and plumbing systems, including Vollservice (full-service) and Teilservice (partial-service) maintenance contracts plus daily 08:00–19:00 emergency service for contract customers.
• Badausstellung (Bathroom Showroom) In-house physical bathroom showroom at Grafschaft-Gelsdorf where customers can experience materials, fixtures, and design concepts in person with guided expert consultation, supplemented by partner showrooms.

Quantifiable outcome

• Hydraulic balancing (hydraulischer Abgleich) typically pays for itself within a few years through reduced energy consumption
• +1 more outcomes

Segments2 records

Ideal customer profiles2 records

Technology focussed No

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature4 records

Partnerships

14 partnerships are on record, tiered core and minor.

• Bad und Fliesen Gruber GmbHcoreStrategic or Co-development Partner · 1 January 2026In 2026, Sonntag acquired Bad und Fliesen Gruber GmbH as part of the company's restructuring into a GmbH & Co. KG. This acquisition expanded Sonntag's capabilities in bathroom design and tiling work, strengthening its competencies in the Grafschaft region.
• ViessmanncoreTechnology or IntegrationViessmann is a premier German manufacturer of heating, industrial, and solar systems. Sonntag installs Viessmann products including heat pumps, condensing boilers, and combined heat/power systems. The partnership provides Sonntag's customers with access to high-efficiency, premium heating technology backed by a leading European brand.
• Stiebel EltroncoreTechnology or IntegrationStiebel Eltron is a German manufacturer specializing in ventilation, heating, and renewable energy systems. Sonntag offers Stiebel Eltron heat pumps and related products for residential and commercial applications.
• GeberitcoreTechnology or IntegrationGeberit is a Swiss-German market leader in sanitary products and bathroom systems. Sonntag installs Geberit sanitary systems and fixtures as part of its bathroom renovation and installation services.
• DuravitcoreTechnology or IntegrationDuravit is a premium German bathroom fixture manufacturer. Sonntag offers Duravit products including toilets, washbasins, and bathroom furniture as part of its bathroom design and renovation services.
• KaldeweicoreTechnology or IntegrationKaldewei is a German manufacturer of premium enamel steel bathroom fixtures including bathtubs and shower trays. Sonntag incorporates Kaldewei products in its bathroom installations.
• HansgrohecoreTechnology or IntegrationHansgrohe is a German manufacturer of premium faucets, showerheads, and bathroom accessories. Sonntag installs Hansgrohe products in its bathroom renovation projects.
• Villeroy & BochcoreTechnology or IntegrationVilleroy & Boch is a premium German-Austrian bathroom fixture and ceramics manufacturer. Sonntag uses Villeroy & Boch products in its bathroom design and renovation projects.
• KeucocoreTechnology or IntegrationKeuco is a German manufacturer of bathroom accessories, furniture, and mirrors. Sonntag offers Keuco products as part of its comprehensive bathroom design services.
• HSK (Duschkabinenbau)coreTechnology or IntegrationHSK is a German manufacturer of shower enclosures and bathroom accessories. Sonntag installs HSK shower cubicles in its bathroom renovation projects.
• ZehndercoreTechnology or IntegrationZehnder is a Swiss manufacturer of radiators, heating systems, and ventilation products. Sonntag installs Zehnder radiators and heating solutions.
• KfW (Kreditanstalt für Wiederaufbau)minorOthersKfW is a German state-owned development bank that provides subsidized financing and grants for energy efficiency and renewable energy upgrades in residential buildings. Sonntag helps customers navigate KfW funding options for heating system replacements and renovations.
• BAFA (Bundesamt für Wirtschaft und Ausfuhrkontrolle)minorOthersBAFA is a German federal agency that administers subsidies for renewable energy systems. Sonntag advises customers on BAFA funding programs for heat pumps, solar thermal, and other renewable energy installations.
• Tiled Layers (Fliesenleger), Drywall Builders (Trockenbauer), Painters (Maler), Carpenters (Schreiner)coreChannel Partner/ Reseller/ DistributorSonntag has a network of long-established, vetted master craftsmen including tilers, drywall builders, painters, and carpenters who are coordinated as part of the company's one-stop bathroom renovation service. These partner trades work seamlessly together under Sonntag's project coordination.

Scale indicators5 records

Recent moves11 records

Expansion highlights6 records

Broad incumbents

• Vaillant: Leading German heating technology manufacturer (gas condensing boilers, heat pumps, ventilation). Competes with Viessmann and Stiebel Eltron in the supply relationship Sonntag relies on, and shapes dealer/installer economics in the German HVAC market.
• Viessmann: Major German manufacturer of heating, industrial, and solar systems. A core technology partner of Sonntag; comparable as the broader incumbent shaping the heating technology ecosystem in which Sonntag operates as an installer.
• REHAU: German polymer-based building solutions provider covering underfloor heating, plumbing, and radiant systems. Comparable as a broad incumbent supplying heating/water distribution technology that regional installers integrate into residential projects.
• Stiebel Eltron: German manufacturer of heat pumps, ventilation, and renewable heating systems. Long-standing technology partner of Sonntag; a broad incumbent whose products Sonntag installs and which competes for end-customer mindshare.
• Buderus: Bosch-owned German heating systems manufacturer with deep installer/dealer footprint. Operates in the same supply ecosystem as Sonntag and influences installer channel dynamics, training programs, and project specifications.

Others

• Hansgrohe: Premium German manufacturer of faucets, showerheads, and bathroom accessories; existing brand partner of Sonntag. Relevant as a brand-ecosystem participant whose dealer network overlaps with regional bathroom installers.
• Geberit: Swiss-German market leader in sanitary products and concealed cistern/wall systems; existing partner of Sonntag. A key upstream supplier and brand participant in the bathroom renovation value chain where Sonntag delivers end-customer projects.

Direct peers

• Thermondo: Berlin-based residential heating installer chain offering standardized heating system replacement (especially heat pumps) across Germany. Directly comparable business model to Sonntag's heating installation vertical but at national scale and with digital lead generation.
• Enpal: Berlin-based solar and heat pump installer offering leasing/subscription models to residential customers. Comparable to Sonntag in target segment and product focus (PV + heat pump) but differentiated by an asset-light financing-led go-to-market.
• 1Komma5°: Hamburg-based heat pump, solar, and EV charging installer scaling a franchise network of local crafts businesses. Closely comparable to Sonntag in core offerings (heat pumps, PV) but combines local execution with central digital, financing, and brand capabilities.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat5 records

Key risks6 records

Key highlights7 records

Customer concentration

• Instagraminstagram.com/sonntag_heizung_sanitaer

Revenue estimate

Valuation estimate

Number of profiles

Profiles7 records

Subsidiaries1 record

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Sonntag