Farmivirta ("Farm Power") is different from traditional electricity contracts in one important thing: every producer can set the price of electricity they generate and sell to the grid. The contract is valid until further notice, and has a period of notice of two weeks.
The selling price of electricity is a consumption-based energy charge (c/kWh). In Farmivirta contract there is no basic charge. Selling prices include VAT 24%, but no transfer (network) costs or energy tax. These are invoiced by your local network company. The prices are for Finland.