diff --git a/app/models/reading.rb b/app/models/reading.rb
index d724fae..eaa8a00 100644
--- a/app/models/reading.rb
+++ b/app/models/reading.rb
@@ -34,11 +34,11 @@ class Reading < ActiveRecord::Base
   # calculate difference with another reading
   # return a hash with differences (self - reading)
   def diff(reading)
-    { :total_kwh_consumed_high => self.total_kwh_consumed_high - reading.total_kwh_consumed_high,
-      :total_kwh_consumed_low => self.total_kwh_consumed_low - reading.total_kwh_consumed_low,
-      :total_kwh_produced_high => self.total_kwh_produced_high - reading.total_kwh_produced_high,
-      :total_kwh_produced_low => self.total_kwh_produced_low - reading.total_kwh_produced_low,
-      :total_m3_gas_consumed => self.total_m3_gas_consumed - reading.total_m3_gas_consumed }
+    { :total_kwh_consumed_high => (self.total_kwh_consumed_high - reading.total_kwh_consumed_high).round(1),
+      :total_kwh_consumed_low => (self.total_kwh_consumed_low - reading.total_kwh_consumed_low).round(1),
+      :total_kwh_produced_high => (self.total_kwh_produced_high - reading.total_kwh_produced_high).round(1),
+      :total_kwh_produced_low => (self.total_kwh_produced_low - reading.total_kwh_produced_low).round(1),
+      :total_m3_gas_consumed => (self.total_m3_gas_consumed - reading.total_m3_gas_consumed).round(3) }
   end
   
   #