ENGO E40-BATW is a battery-powered ZigBee 3.0 / 868MHz smart thermostat, designed as a wireless, surface-mounted successor to ENGO's E25 range. Because it runs on batteries rather than a mains connection, it can be fitted to a wall without chasing in cable or breaking into the existing electrical circuit, making it well suited to retrofits and radiator upgrades where running a new mains feed isn't practical. It communicates with ENGO receivers, relays, control modules, and electronic radiator valve heads over the 868MHz radio band, and can control up to six radiator valves from a single thermostat for even heat distribution across a larger room. Available in white.
Up to 6
Radiator valves controlled
Battery specification discrepancy
ENGO's own product listing gives two different battery specifications for this thermostat: the technical data table states 2x AA batteries, while the accompanying installer benefits text states 2x AAA. We have used the technical data table (2x AA) as the authoritative figure on this page, but recommend confirming battery type against the physical unit or quick guide before ordering spares.
ZigBee gateway required for app control
Full remote scheduling and app control via ENGO Smart requires a compatible ZigBee gateway, purchased separately. Without a gateway, the thermostat still operates fully via its own display and ENGO binding function, but cannot be controlled remotely or via voice assistants.
Key Features
Battery power means no mains wiring
Fitting the thermostat is a case of mounting the backplate and inserting batteries; there's no need to run a new cable back to a fused spur or existing circuit, which keeps installation quick on retrofit and radiator-upgrade jobs.
Controls up to six radiator valves from one thermostat
A single E40-BAT can command up to six electronic radiator valve heads over the 868MHz link, so one thermostat can manage every radiator in a larger room or open-plan space rather than needing a valve-mounted controller per radiator.
ENGO binding keeps the system working offline
The ENGO binding function pairs the thermostat directly with receivers, relays, and valve heads without relying on cloud automation, so the heating schedule continues to run even if the internet connection or gateway is temporarily unavailable.
TPI and adjustable hysteresis control
Precise temperature holding is handled by a TPI algorithm, with adjustable hysteresis from ±0.2°C to ±2.0°C for installers who need to tune response for a particular room or heat-emitter type.
PIN-protected key lock for shared or public spaces
Settings can be locked with a PIN code, preventing accidental or unauthorised changes to the setpoint in households with children or in commercial spaces such as offices and communal areas.
Continues to run through mains power cuts
Because the thermostat itself is battery-powered, it keeps displaying and applying its schedule during a mains power outage, even if the boiler or heat source it's controlling cannot run.
Technical Specification
| Power |
| Power supply |
2x AA batteries |
| Temperature Control |
| Setpoint range |
5.0°C to 45.0°C |
| Display accuracy |
0.5°C |
| Control algorithm |
TPI, hysteresis (±0.2°C to ±2°C), Delta RCWC |
| Connectivity |
| Communication |
ZigBee 3.0, Radio 868MHz |
| Radiator valve support |
Up to 6 electronic radiator valve heads |
| App platform |
ENGO Smart (ZigBee gateway required for remote/app control) |
| Physical |
| Dimensions |
80 x 80 x 23mm |
| Mounting |
Surface-mounted |
| Colour |
white |
Frequently Asked Questions
Do I need a gateway to use this thermostat?
No gateway is required for local, on-device operation and pairing with receivers or radiator valves via ENGO binding. A ZigBee gateway is required for remote scheduling, app control, and voice assistant integration.
How many radiator valves can one thermostat control?
Up to six electronic radiator valve heads can be linked to a single E40-BAT thermostat, allowing one unit to manage every radiator in a room.
What batteries does this thermostat use?
ENGO's technical specification lists 2x AA batteries; please see the amber note above regarding a discrepancy in the manufacturer's own documentation on this point.
Will the heating schedule still run if I lose Wi-Fi or the gateway goes offline?
Yes. Schedules are stored on the thermostat and continue to run via ENGO binding without an active internet or gateway connection.
Is this thermostat suitable for underfloor heating as well as radiators?
Yes, the E40-BAT is compatible with both underfloor heating and radiator heating systems when paired with the appropriate ENGO receiver or valve head.
