Heat pump install 1 - Vaillant Arotherm Plus

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 Why a heat pump?

Our house is on a communal LPG system, with significantly higher prices than mains gas and some historical issues with the supplier that made the future prices even more uncertain.

The existing (non-condensing) boiler was about 11 years old and slowly dyeing on us.  The choice was not a simple one.  A heat pump would be a 'lot' more expensive, but should be cheaper to run.  Gas would be much easier, but it seemed silly to put in a new boiler which would last 10-15 years when we are supposed to be moving away from gas rapidly.

Price comparison

Quote for a Worcester Bosch Greenstar 30i lpg including install:
£2,600

Quote for an aroTHERM plus 12kW and heat pump install:
£15,000

The heat pump itself was only £5,300 the major additional costs include:
A new water tank (£1,000)
New radiators due to the lower temperature flow (£2,000)
New piping kits for the system (£1,000)
Electrical works (£800)
Installation (£3,000)

Other benefits

The government incentive scheme offers a payment over a period of 7 years for heat pump installs

RHI return:
£10,400

There are also cheap loan schemes that can cover much of the up-front cost.  That takes the total cost (assuming you can get a 0% loan) to:
£4,600

That's 2k more than the gas option BUT there is also the cost of fuel to consider. Our LPG came in about 9p per KWh  Electric is at 16p.  The heat pump uses electricity but the COP (Coefficient Of Performance) is a ratio that describes the additional heat you get for each unit of electricity consumed.

Although the Vaillant system  advertises a seasonal average COP of  'up to' 5.03, this seems very unlikely in the Scottish Highlands.  Assuming an average COP of 3, this would take the effective electric cost down by a factor of 3, to 5.3p.  That saves 3.7p per KWh consumed.

The estimated electric required for the heat pump is 5,000 KWh per year, so the saving would be around £185 a year, so another £1,295 over the next 7 years

Total cost with this now calculated with this included is:
£3,305

This is now getting pretty similar to the cost of the gas system.  If the cost of gas rises in comparison to electricity over the next few years which seems likely right now, this could get a better.  a COP of 3 is also pretty pessimistic so I hope we can do better.

Cheaper options

We originally planned to go with a Mitsubishi Ecodan but with COVID and supply issues, we just could not get one.  If we had, this would have saved about £1,000 at current costs.

There are cheaper options still BUT there always are, and if you go low enough, these would be poor quality units that would not likely not last long enough to be worth it.



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