The domestic renewable heat incentive:
You have your property assessed for its heating requirements, this gives an estimated figure for the number of kWh heat demand in a year. Let's say it comes out at 30,000 and you get an EPC certificate showing this.
You have an MCS registered company fit an air source heat pump sized suitably to the heating demand of the house, with reference to the type of heat emitter (underfloor, or oversized radiator usually), and you get an MCS certificate
you apply to ofgem for the RHI grant, they assess your application and start making quarterly payments for 7 years, into your bank account, either based on an equation related to the heat demand and efficiency of the pump, or they have you fit a meter and pay you based on that
The equation is relatively simple.. Heat pumps produce more heat energy than they consume. In typical conditions a heat pump should produce 3kwh of heat for every 1 kWh of electricity used. That means to provide the 30,000 above will require 10,000kwh of electricity. Because the heat pump generates the difference of 20,000 "by renewable magic" that is what you get paid on. The current payment rate for an air source heat pump is (allegedly) 10p per kWh so that's around 2 grand a year or 500 a quarter, for 7 years..
Some installations require meters to be fitted, maybe most will in future. If metered you're paid for what the meter says you've used rather than the estimate
My 5k was definitely cheap, my unit isn't ErP marked (as they must now all be) and had to be installed by a certain date. As it had a short shelf life, the unit was cheap and I put the underfloor heating in myself. Their plumber connected the machine, you have to have a G3 cert to work on sealed systems. My father in law had a similar machine and uh system installed by he now defunct Ice Energy, his cost was around 13k, and he'll get 11k back
The current scheme has a cap on the number of units you can claim for, so there's an incentive to reduce the heat demand of your house if it needs more heat, but the slight flaw in the govt plan is it doesn't exactly encourage people to insulate their homes as best they can before installing such a tech. However, the poorer the insulation the harder the tech has to work so the more risk of knackering it up..
Many kinds of tech can be claimed for, for more info Google the RHI
One of the best aspects of ground and air source heat pumps is that they're clean and quiet, have minimal maintenance requirements (they're basically reverse refrigerators?) and need only electricity. They can be plumbed in by a DIY person and you'd only need a G3 certified person if you install a mains pressure hot water tank so if you have the appetite for it you can cut your costs. To be valid for rhi he system must be installed by an MCS registered member company and they do charge a premium to cover their membership.. Eg your local mate plumber could install an ASHP for eg 5 grand components and labour. The same thing from an MCS co would be more like 8, but you can then claim the RHI and get most or more of it back
The guys that installed mine were great to deal with and good value, they're down your way (but they travelled 200 miles to fit mine).. PM me if you'd like their info