Feed-in tariff
The Feed-In Tariff was a scheme which offered payment from the Government (but paid via an energy supplier), to households in England, Scotland and Wales for all the electricity they generated via a renewable source. The rate was 4.07p/kWh.
The feed-in tariff was income tax-free and paid quarterly by energy suppliers. It was guaranteed for 20 years, and was index-linked so it rose with inflation. The Energy Saving Trust estimated that panels registered at a typical home could typically earn £150/year under the feed-in tariff.
Export tariff
This was a payment for energy you didn't use, which was sent back to the grid (unless you had an export meter, it was normally assumed there was a 50:50 split). It was set at 5.03p/kWh.
You needed a 'D' rating on your Energy Performance Certificate (EPC) to get the full feed-in payment (4.07p/kWh in July 2017). If you were below D, this fell to 0.43p/kWH, making the incentive considerably less attractive. You need an EPC if you're selling any property or are a landlord; these are valid for 10 years.
The Feed-in Tariff Scheme has now been replaced by the Smart Export Guarantee Scheme, which reimburses households for the surplus energy generated through eligible sources (i.e. solar panels) which is exported back into the National Grid.