The service costs 3,99€/month. If you are not a WATT+VOLT client the purchase of the service is carried out with the purchase of the Gateway device from the e-shop of smartwatt.gr, by paying in advance the amount of 3,99€ x 12months=47,88 € per year. If you are a WATT+VOLT client, the payoff of the service is done by paying 12 equal instalments of 3,99€, in your monthly energy bill from WATT+VOLT.