Wireless GRMS Retrofit for Existing Hotels: HX Series

The Retrofit Problem Every Hotel Owner Knows

You manage a 200-room hotel built in 2005. The guest rooms have basic lighting switches, a standalone thermostat, and a door hanger for Do Not Disturb. No occupancy detection. No energy setback when rooms are empty. No integration with your PMS. Guests control the air conditioning manually and leave it running at full blast when they check out.

You know a modern GRMS would cut your energy bill by a third and lift your guest satisfaction scores. But every supplier you speak to tells you the same thing: full GRMS requires a dedicated two-wire bus running to every room, new wiring through walls and ceilings, and a floor-by-floor installation that means closing rooms for weeks at a time.

For a hotel that cannot afford to close floors -- which is most hotels -- that answer is a dead end.

Smart G4's HX Series was built specifically to solve this problem. It delivers full hotel GRMS functionality to existing properties with zero new wiring, using a proprietary wireless mesh protocol that runs on the 2.4GHz band with frequency-hopping for reliability. Installation is non-invasive, room-by-room, and can be completed floor by floor without taking the hotel offline.

What the HX Series Actually Delivers

The HX Series is not a simplified or stripped-down GRMS. It delivers the same core functionality as Smart G4's wired series, through wireless hardware designed for the specific constraints of hotel room retrofit:

Energy Management

• Key card energy saver: The HX wireless key card holder cuts all non-essential loads when the guest removes their card. Compatible with existing key card systems -- no lock replacement required.
• Occupancy-based HVAC setback: The HX Breathing Sensor detects room occupancy using microwave radar (not PIR, which misses sleeping guests). When the room is vacant, HVAC steps back to a setback temperature. When occupancy is detected, it returns to the comfort setpoint automatically.
• 40A heavy energy saver: For rooms with high-draw loads (electric water heaters, large HVAC units), the HX 40A relay handles the load directly -- no additional contactor required.
• Door/window magnetic contact: When a window or balcony door is opened, the HVAC pauses automatically. This single feature alone recovers 8-12% of room HVAC energy in warm climates.

Guest Control

• HX Bedside Panel: Replaces the existing bedside switch plate. Controls lighting scenes, curtains, DND/MUR, and room temperature from a single panel. Available in standard and premium finishes to match existing room decor.
• HX Bathroom Panel: Adds lighting and ventilation control to the bathroom without new wiring.
• HXD Dynamic Display Panel: An all-in-one panel combining thermostat display, lighting control, and service request in a single unit -- ideal for rooms where wall space is limited.
• Hotel App integration: Guests can control all room functions from the Smart G4 hotel app on their smartphone, without touching any physical panel.

Service and Housekeeping

• DND/MUR wireless bell set: Replaces the existing door bell and service request panel. Staff see room status on the floor management display in real time.
• Wireless curtain motor: Battery-powered or solar-powered motorised curtain motor installs on the existing curtain track with no wiring. Controlled from the bedside panel, the hotel app, or automatically on check-in/check-out.

How HX Wireless Mesh Works

The HX Series uses a proprietary mesh protocol, not standard Zigbee or Z-Wave. This is a deliberate design choice:

• Frequency hopping: The protocol hops across 16 channels in the 2.4GHz band, avoiding interference from hotel Wi-Fi networks, guest devices, and neighbouring rooms.
• Mesh redundancy: Each HX device acts as a repeater for its neighbours. A floor of 20 rooms creates a self-healing mesh -- if one device loses signal, the network routes around it automatically.
• Range: Each HX device has a line-of-sight range of 80 metres. In a hotel corridor environment with concrete walls, effective room-to-room range is 15-25 metres, which is sufficient for standard hotel floor layouts.
• HX Gateway: One HX Gateway per floor (or per 20-30 rooms) bridges the wireless mesh to the hotel's wired LAN. The gateway connects to the Smart G4 GRMS server over standard Ethernet -- no special cabling required.

This architecture means the HX Series integrates fully with Smart G4's central GRMS platform, including PMS integration, energy reporting, and the hotel management dashboard.

Installation Process: Room by Room, Floor by Floor

The HX retrofit process is designed to minimise disruption to hotel operations:

Phase 1: Gateway Installation (1 day per floor)

The HX Gateway mounts in the existing floor distribution board or a small surface-mount enclosure in the service corridor. It connects to the hotel LAN via a standard RJ45 patch cable. No new cable runs are required -- the gateway uses the hotel's existing data network.

Phase 2: Room Device Installation (2-4 hours per room)

Each room is retrofitted independently. A two-person team can complete a standard room in 2-4 hours:

1. Replace the existing key card holder with the HX wireless key card energy saver
2. Replace the bedside switch plate with the HX bedside panel
3. Install the HX Breathing Sensor on the ceiling (surface mount, battery powered for the first 3 years)
4. Install the HX door/window magnetic contacts on balcony doors and windows
5. Replace the existing door bell with the HX wireless bell and service request set
6. Install the HX wireless curtain motor on the curtain track
7. Commission the room in the Smart G4 GRMS app -- typically 15-20 minutes per room

Because each room is independent, the hotel can retrofit one floor at a time while keeping all other floors fully operational. A 200-room hotel can typically complete the full retrofit in 3-4 weeks of rolling installation.

Phase 3: PMS Integration and Commissioning

Once all rooms on a floor are commissioned, PMS integration is activated. The HX Series supports the same PMS connectors as Smart G4's wired series: Opera, Mews, Cloudbeds, and other HTNG-compliant PMS platforms.

With PMS integration active, the GRMS receives check-in and check-out events in real time. On check-in, the room pre-conditions to the guest's preferred temperature (if stored from a previous stay). On check-out, the room enters full energy setback mode immediately -- not after a 30-minute timeout.

ROI: What the Numbers Look Like

The HX Series retrofit delivers measurable ROI within 18-30 months in most hotel environments. Here is a worked example for a 200-room hotel in a warm climate:

Baseline assumptions:

• Average room energy cost: $8.50/day (HVAC dominant)
• Occupancy rate: 72%
• Rooms occupied per day: 144
• Annual room energy cost: $144 × $8.50 × 365 = $446,940

HX Series energy reductions:

• HVAC setback (vacant rooms): -18%
• Door/window contact HVAC pause: -9%
• Key card energy saver (non-HVAC loads): -6%
• Total reduction: approximately 33%

Annual energy saving: ~$147,500

HX Series retrofit cost (200 rooms, installed): $220,000-$280,000 depending on room configuration and finish level.

Simple payback: 18-23 months.

This calculation excludes the revenue impact of improved guest satisfaction scores, reduced maintenance call-outs from predictive fault detection, and the competitive positioning benefit of being able to market the property as a smart hotel.

HX Series vs Wired GRMS: When to Choose Each

Criteria	HX Wireless Series	Wired sBUSPro Series
New-build or full renovation	Not recommended	Recommended
Existing hotel, no renovation	Ideal	Not practical
Installation disruption	Minimal (room by room)	Significant (floor closure)
Total installed cost	15-25% higher than wired	Lower for new-build
Long-term reliability	Excellent (mesh redundancy)	Excellent (wired)
PMS integration	Full (Opera, Mews, Cloudbeds)	Full
Energy saving potential	30-40%	35-45%
Payback period (warm climate)	18-30 months	14-24 months
Suitable for phased rollout	Yes	Limited

For hotels planning a full gut renovation, the wired sBUSPro series remains the better long-term investment. For hotels that need GRMS functionality without closing floors, the HX Series is the only practical path.

Which Hotel Types Benefit Most from HX Retrofit

Mid-Scale and Upper-Midscale Hotels (3-4 Star)

These properties typically have the highest energy waste per room relative to room rate. They were built before GRMS was standard, and they cannot justify the cost of a full renovation. The HX Series delivers the energy savings and guest control features that close the gap with newer 5-star competitors -- at a capital cost that fits a mid-scale budget.

Serviced Apartments and Extended-Stay Properties

Long-stay guests are the highest energy consumers per occupied room. An extended-stay guest who leaves the air conditioning running at 18 degrees while they are out for the day costs the property significantly more than a transient guest. The HX occupancy sensor and door/window contact combination is particularly effective in this segment.

Heritage and Boutique Hotels

Properties in listed buildings or heritage structures cannot run new cable through walls and ceilings. The HX Series is often the only GRMS option available for these properties. Smart G4 has completed HX retrofits in properties dating back to the 19th century, where the only permitted installation method was surface-mount or wireless.

Hotels Undergoing Soft Refurbishment

A soft refurbishment -- new soft furnishings, redecoration, no structural work -- is the ideal moment for an HX retrofit. The room is already partially stripped, access is easier, and the installation can be completed within the refurbishment window without extending the room closure.

Conclusion

The HX Series removes the single biggest barrier to hotel GRMS adoption: the requirement for new wiring. For the hundreds of thousands of hotel rooms worldwide that were built before GRMS was standard, wireless retrofit is not a compromise -- it is the only viable path to modern guest room automation.

Smart G4 has completed HX Series retrofits across 40+ countries, in properties ranging from 50-room boutique hotels to 600-room city centre towers. The combination of zero-wiring installation, full PMS integration, and a 18-30 month payback period makes the HX Series the most commercially compelling GRMS product in the retrofit market.

Ready to assess your property for an HX Series retrofit? Explore Smart G4 Hotel GRMS Solutions and contact our team for a site assessment and ROI projection tailored to your property.