In a potential political headache for the Nationals, eight of the 10 NSW seats with the highest proportion of households with solar installations are all held by the party.

In the National Party-held seats of Barwon and Lismore 36 per cent of voters live under rooftops with solar installations, the highest share in the state. In the electorate of Tweed the proportion is 30 per cent and in Port Macquarie 28 per cent, analysis by solar advocacy group Solar Citizens shows.

State-based solar bonus schemes for energy fed into the power grid from small-scale rooftop systems underpinned the strong household take-up of solar power, especially in regional NSW. But these schemes will expire on January 1, leaving many households with rooftop solar panels out of pocket.

Solar Citizens consumer campaigner, Reece Turner, estimates that the 147,000 NSW households receiving a solar bonus will experience an average "bill shock" of about $1600 per year after the schemes are withdrawn.

"There's going to be a lot of unhappy solar owners out there," he said.

The financial impact will be felt disproportionately in regional areas where the take-up of solar rooftop installations by households has been high. But the change will have relatively little impact on many wealthy inner-Sydney electorates, where the proportion of solar rooftop installations has been small. The analysis by Solar Citizens found that in the electorate of North Shore just 2 per cent of voters have a solar installation and in the seat of Coogee the share is 3 per cent.

The withdrawal of solar subsidies comes at a difficult time the Nationals. Earlier this month the party lost the safe seat of Orange to the Shooters, Fishers and Farmers party after a massive swing which highlighted voter discontent over recent Baird government decisions including council amalgamations and the ill-fated ban on greyhound racing.

Solar Citizens will launch a campaign on Monday calling on the NSW government to ensure a "fair" price for the state's solar owners.

It says the 5-6c per unit for rooftop solar electricity paid by big power companies to solar owners for their surplus electricity that goes back into the grid is far too low. Solar Citizens estimates this power is on-sold to neighbours – sometimes travelling only a few metres down the poles and wires – for 29c per unit on average.

Mr Turner said the "Fair Price for Solar" campaign would target areas where there is high solar uptake, such as regional NSW.