Energy policymakers gave the green light to start buying solar power generated from private buildings and households once again after postponing the programme for more than four years.
Private buildings and households that are accepted by the programme will sell surplus solar power to the state's utilities.
Energy Minister Siri Jirapongphan said the Department of Alternative Energy Development and Efficiency is carrying out studies to outline the investment conditions, which are expected to be concluded this year.
He said there is no solid time frame yet because details such as business model, investment budget, power tariff, net metering system, supporting region and capacity from each building are still under development.
The tightened condition is the power tariff to sell back should be up to 2.44 baht per kilowatt-hour.
Mr Siri said policymakers are confident that the cost to develop rooftop solar photovoltaic panels has declined.
The programme will allow for households to sell power either under a business-to-business model or to sell surplus electricity wholesale to the state.
"We are working to support households to participate in the power generation from their own rooftops and to receive revenue from selling the surplus electricity," Mr Siri said.
This programme is aimed at achieving policymakers' goal to have all types of renewable energy make up 30% of the country's total power generation by 2036 from 10% at present.
The policymaker expects to see a decline in heavy dependence on fossil-based power in the long run. Fossil fuels make up 85% of national power.
Mr Siri said the programme may be accelerated to increase the proportion of renewable energy and meet the target sooner than projected.
Biomass and biogas are becoming mainstream energy sources, with combined capacity of more than 3,000 megawatts.
The rooftop programme was launched for the first time in 2013 with a total quota of 200MW.
Bangkok, Nonthaburi and Samut Prakan were allocated 80MW of the total, equally distributed between private buildings and households.
At the time, the power tariff was set at 6.10-6.96 baht per kilowatt-hour, higher than for the upcoming programme.
Since then, the programme has faced political conflicts and has not been promoted, leaving huge solar power projects of 2,000MW pending during 2014-16.
Somruedee Chaimongkol, director of Banpu Infinergy Co, a solar energy provider, said the company welcomes the programme and is ready to comply once the investment conditions have been made clearer.
She said the company is confident the current power tariff is competitive and fair, relative to its business partnerships with smart energy service providers.
The company provides a combined capacity of 12MW and has another 100MW in its backlog.
Banpu Infinergy is also set to achieve 300MW of capacity from solar energy to serve future demand in accordance with the Energy Ministry's Alternative Energy Development Plan
Solar rooftop owners operate as independent power suppliers (IPSs). The Energy Regulatory Commission reported that registered IPSs have a combined capacity of 2,600MW and more new IPSs are being launched each month with an average capacity of 4-5MW.
IPS capacity accounts for 6.5% of the total power generation system.