In October 2012 the government published proposed details of the Renewable Heat Incentive (RHI), a subsidy scheme to encourage homeowners to switch to green central-heating systems. It is similar to the “feed-in tariffs” (FiT) available since 2010 to households that install solar pv panels. For many homeowners it turned out to be even more profitable — especially because the solar tariffs have now been cut drastically. What’s more, any system installed after July 15, 2009, will be eligible.

As with solar panels, subsidy payments will be based on how much energy you generate, with a proposed rate of 5.2p-8.7p per kilowatt hour (kWh) in the case of a biomass boiler. Yet the payments will be much more concentrated — into a period of just seven years, compared with 20-25 years for solar. Factoring in fuel savings, many who have installed a renewable energy system calculate that it will pay for itself in only five years.

The RHI, which came into force for domestic installation in April 2014, will be available for several forms of green heating. Biomass boilers — fired by wood chips or pellets — will be eligible, as will ground-source and air-source heat pumps. These work on the same principle as a fridge or air-conditioning, except that they are installed in reverse, to raise the temperature rather than lower it. A ground-source heat pump transfers energy from the earth via a length of underground pipe; an air-source system, as its name suggests, extracts heat from the air.

Alternative to Oil – Green Renewable Energy – Mitigating Climate Change

All of this is particularly attractive to properties in “off gas” areas such as rural Devon and Dartmoor where the incentives and benefits of switching to green, renewable energy for their heating and hot water suppy which currently is mostly provided by oil-fired boilers therby mitigating their contibution to cliamate change.

Payback times under the RHI could be short compared with those for solar power. According to an established renewable energy business that installs heat pumps in Devon, an air-source unit costing £6,5 K could generate payments of £2,660 a year. Yet energy from a heat pump, unlike that from solar panels, is not free: the pump consumes large amounts of electricity. Replace your oil boiler with one and you will be swapping an oil bill for higher electricity bills. Whether that makes sense depends on the relative costs of oil and electricity over the next few years, which are impossible to predict.

Renewable Energy in Devon – Case Studies

One happy customer is Henry Onker, the owner of a 17th Century granite built hotel, restauarant and pub on Dartmoor. Three years ago, he replaced his Devon country house hotel’s oil-fired boiler with a ground-source heat pump that extracts heat stored below the surface of the grounds. The system, installed by a Microgeneration Certificatation Scheme (MCS) approved installer cost £185,000, some of which was covered by a listed-building grant. He says his heating bills went down from £80,000 to £14,000 a year.

MCS-logoIt is worth noting that you must choose a renewable energy installer who is MCS accredited in order to qualify for any RHI payments.

A ground-source heat pump would not have been practical for Tarquin and Zara at their four-bedroom home in Chagford, also in Devon — it would require as much space as a tennis court — but they are delighted with the £10,000 air-source system installed last year. They were burning 2,000 litres of heating oil a year, at a cost of £1,200. They no longer have an oil bill, but do have a larger electricity bill. Nevertheless, they calculate that operating the heat pump has cost him only £500 in electricity — resulting in a net saving of £700 a year on fuel.  They are now looking at lowering the electricty costs if an alternative source of green electricity is used – solar pv or wind turbines serve rural areas of Devon very well. Many specialist companies that promote renewable energy in Devon are able to design, supply and maintain an integrated system that includes a heat pump, underfloor heating and solar pv panels for additional electricity from renewable sources.

Underfloor Heating

The standard advice about air-source heat pumps is that they work better with underfloor heating than with radiators: the pumps run less efficiently at the higher water temperatures required by the latter.

underfloor heating

The above image shows and underfloor heating installation project.  These are especially efficient ways to heat a home when using renewable energy from heat pumps.

Not all heat pumps installed in British homes have proved as satisfactory. A study conducted by the Energy Saving Trust in 2010 monitored 83 installations of ground- and air-source heat pumps for a year. It found that in 80% of cases, the ratio of heat produced to electricity consumed was less than 2.6 — the level at which a heat pump qualifies as a renewable source of energy under the EU Renewable Energy Directive.

The worst case — an air-source heat pump feeding a radiator central-heating system — had an efficiency rating of only 1.2, which meant it was using almost as much electricity as heating the property with electric fires would have consumed. The study blamed poor design and shoddy installation, with the work often carried out by contractors who did not properly understand the systems.

For anyone worried about ditching their boiler, the RHI would allow householders installing heat pumps to retain their old system as a backup. Still, given that this a relatively new technology in Britain, switching to a heat pump may still strike a lot of homeowners, especially those in older properties, as a bit of a gamble — even with some strong encouragement from the government.