Energy switching company, WeSwitchU.ie, also warned of the pitfalls farmers need to look out for when seeking a better deal.
Farmers with 200 cows can benefit most by trading in their current supplier for a new one, according to the company.
It reveals a €6,400 gap between the cheapest and most expensive electricity plans on the market.
For a farmer with 150 cows, the index reveals savings of €4,220 for electricity customers 10,058 versus €5,838 per annum), and €2,215 for a farmer with 100 cows (€5,635 versus €3,420 per annum).