Pellmon runs very well on a raspberry pi II which draws about 2.3W or less. It also gives you full control of all settings, not just the read only data available by parsing json from stokercloud. OpenHAB integration is admittedly not as simple as "dpkg -i pellmon.deb", you also need pellmonMQTT which is a separate project, and then you need to make mqtt bindings for openHAB. You can also get everything from the pellmon webinterface with http GET, but the 'api' is not made with that in mind. It's just made for the frontends needs. For instance /getparam/advanced_data-boiler_power_kw
returns {"value": "5.0", "param": "advanced_data-boiler_power_kw"}
(With a V7/V13)