Deciding to use insert or update depending if unique key is in table

Question

So I have a table which will be keeping an average energy usage for specific stores at specific temperatures.

Store + Temperature(Integer) is not in table -> Add to the table

Store + Temperature is in table -> Use two of the rows parameters
                                   to find the new average and update the row

If my table looks like this

CREATE TABLE public.temperatures (
  temp_id           serial NOT NULL PRIMARY KEY,
  temp_station_id   integer,
  temp_value        double precision,
  temp_curr_kwh      double precision,
  temp_value_added  integer,
  temp_kwh_year_1   double precision  (default 0)
)

I found this answer similar to my question but it is for mySQL, would this work for postgres?

ALTER TABLE temperatures ADD UNIQUE (temp_station_id, temp_value);

and execute the following statement

INSERT INTO temperatures (temp_station_id, temp_value, temp_curr_kwh)
SELECT temp_station_id, temp_value, temp_curr_kwh
FROM   temperatures
WHERE  temp_station_id = 'STATION_NAME_VAR' AND 
       temp_curr_kwh = 'KWH_VALUE_VAR'
ON DUPLICATE KEY UPDATE temp_curr_kwh = ((temp_curr_kwh * temp_value_added) + KWH_VALUE_VAR) / (temp_value_added + 1),
                        temp_value_added = temp_value_added + 1;

So if the station and temperature exist, it takes the old temp_curr_kwh (average) multiplies it by the number of values added so far temp_curr_kwh * temp_value_added then add the new kwh value and then divide the new sum by the temp_value_added + 1

Before I try the code I wanted to check to see if this could be optimized or done differently?