I started my Home Assistant instalation a few day ago and now added these sensors to it (will make a window reed contact next on the same base).

The ESP ist running on the ESPhome software (you can find a good guide in how to wire up the esp12 here - http://domoticx.com/esp8266-wifi-esp-12-module-aansluiten/). For the deep sleep mode you need to connect the GPIO16 pin to reset. Otherwise the ESP will not wake up.

I'm using the following code in ESPhome - for the first test you can delete the deep sleep lines at the end.
With one meassurement every 10min. it should run for at least 6 month on two AA Eneloops. The ESP cunsumes ~70mA when active and 0,017mA when in deep sleep.
Right now I'm waiting for the 5mm nickel stripes for proper battery contacts.

esphomeyaml:
name: bme280
platform: ESP8266
board: esp12e

wifi:
ssid: 'XXXXXXXXXXXXXXX'
password: 'XXXXXXXXXXXXXXX'
manual_ip:

static_ip: 192.168.0.23gateway: 192.168.0.1subnet: 255.255.255.0

logger:

api:

ota:

i2c:
sda: 4
scl: 5
scan: False

sensor:

• platform: bme280
  temperature:
  name: "BME280 Temperature"
  id: bme280_temperature
  pressure:
  name: "BME280 Pressure"
  id: bme280_pressure
  humidity:
  name: "BME280 Realtive Humidity"
  id: bme280_humidity
  address: 0x76
  iir_filter: 16x
  update_interval: 1s
• platform: template
  name: "Altitude"
  lambda: |-
  const float STANDARD_SEA_LEVEL_PRESSURE = 1013.25; //in hPa, see note
  return ((id(bme280_temperature).state + 273.15) / 0.0065) * (powf((STANDARD_SEA_LEVEL_PRESSURE / id(bme280_pressure).state), 0.190234) - 1); // in meter
  update_interval: 1s

• platform: template
  name: "Absolute Humidity"
  lambda: |-
  const float mw = 18.01534; // molar mass of water g/mol
  const float r = 8.31447215; // Universal gas constant J/mol/K
  return (6.112 powf(2.718281828, (17.67 id(bme280_temperature).state) / (id(bme280_temperature).state + 243.5)) id(bme280_humidity).state mw) / ((273.15 + id(bme280_temperature).state) * r); // in grams/m^3
  update_interval: 1s

• platform: adc
  pin: VCC
  name: "ESP voltage"
  update_interval: 1s

deep_sleep:
run_duration: 3s
sleep_duration: 600s