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We were approached by the customer to come up with a solution to heat three separate dwellings on their farm in the Marden, Kent area. 


They wanted to make the best use of a solar farm that they already had installed on the site. The company that installed the solar farm did so on the basis that they would supply and install the equipment and receive the Renewable Heating Incentives (RHI), and that the customer could buy the electricity whilst being generated for 6 pence per unit. 


Planning & Installation


The properties on the farm comprise of the 'Farmhouse' where the customer lives, the 'Oast House' rented for residential use, and the 'Barn' which is rented out as office space. We carried out various upgrades to the current heating systems in all of the properties and made recommendations for simple insulation upgrades. 


We arranged for a timber-framed plant room to be built to our specification to house the heating and hot water equipment. We then installed a 45kW Thermia Mega M three-phase Ground Source Heat Pump along with all the necessary equipment to serve all three properties.


Each property is individually metered for heating & hot water usage and pre-insulated pipework.


Results from heat pump installation

The heat pump is returning on average 3.5 units of heat for every 1 unit of electricity used through the summer months providing 100% of the hot water. The heat pump is providing over 4 units of heat for every unit of electricity used in the winter months for both heating and hot water.


As an indication, an immersion heater returns one unit of heat output for every one unit of electricity.



Client Review

"Our pump is rated at 45 KWth, this means our Tier 1 ceiling is 45 x 1314  =  59,130 (please check this before publishing)

The input electricity of the scheme September - September was 21,383 KWh.

Output was 68,830 plus 13,124 (hot gas) = 81,954.

Less input electricity 81,954 – 21,383 = 60,571 KWh of generated sustainable heat. 


We do get paid on everything that comes out of the main output meter though, so we are actually paid for whole 81k KWh. However, the cap comes down at 59130 units, and the Tier 2 payments are much less generous. I think that this means we will earn about £6k/pa [index linked] for 20 years. Less maintenance and repairs, and also less electricity costs, this is a modest but useful return on our investment. 


To us, it is important that it is index-linked. So this is effectively a government bond – a safe form of saving.


The other thing is that we are currently charging our tenants for heat and hot water as metered via the system. We have just raised this price from 5p to 6p, which we still think represents good value for money. The hot water supplied, we work out what it has cost to heat, and allocate that cost based on how much each has consumed.


As the heat pump is used to sell heat to our customers, we were able to recover the VAT, as our business is registered as a farming/ power generation company. As you are aware, we benefit from cheaper electricity costs from our solar array."


Potential new jobs

We may well be interested in a shared loop system for our next project after the barn. Our ultimate plan would be 5 dwellings in one yard development. So we may be looking at that in the future, planning permitting.

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