Currently Highland customers face a 2p electricity surcharge which leaves them paying more – despite the region facing some of the highest rates of fuel poverty.
The region is also a key generator of renewable energy.
SNP MSP Kate Forbes said: “Highland Scotland is energy-rich, with huge potential as a green energy powerhouse.
“The SNP’s commitment to establishing a publicly owned, not-for-profit energy company will ensure that the public have greater choice and the option of a supplier whose only job is to secure the lowest price for consumers.
“But residents in the Highlands face a completely unfair surcharge on their bills, despite the region facing amongst the highest rates of fuel poverty and being most exposed to extreme weather.
“If Theresa May is serious about tackling high electricity bills, it’s time for her to end the Highland energy rip-off and tackle this surcharge as part of her price cap.”
There are 14 regions across the GB electricity market, which means suppliers charge different prices depending on geographical issues associated with transporting energy.
A ScottishPower spokesman said: “We seek to offer competitive prices across all areas of Britain, reflective of the costs associated with distributing electricity in different regions. We have worked hard with our own customers to get the majority on to our best products and off standard variable prices, well ahead of the other large suppliers.”
A spokesman for the department of business, energy and industrial strategy said: “As Ofgem’s analysis showed, a single national charge would see 16 million households’ energy bills increase. While we do not support a move away from the current system, we do welcome Ofgem’s work to introduce tougher price controls.”