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Green Home NE733 - Gordon Smith installed solar PV and an air source heat pump to be energy efficient and reduce bills in Milltimber, Aberdeenshire

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When Gordon Smith and his family were building their new home, they wanted to make it as energy efficient as possible. Minimising their energy bills was particularly important to them as they were approaching retirement age and they wanted to keep their outgoings to a minimum.

Installing solar panels with battery storage

Gordon installed 3.84kWh of solar photovoltaic (PV) panels on the roof and a 12.5kWh Sonnen battery in the garage. The battery stores any electricity generated by the solar panels for use at a later time.

The family tracks the electricity generated and used via an app, and the combination of panels and battery means that they generate about 35-40% of the electricity they use each year.

In addition to this, they have a Zappi car charge to charge their hybrid vehicle, which means “we only have to buy petrol when we go on long journeys.”

Installing an air source heat pump

The family didn’t want to install a gas boiler “because of issues around their future viability” and because they didn’t want to pay to get a new gas supply installed and pay a standing charge for a minimal use of gas. This meant that they would be fully electric and because they wanted underfloor heating, it meant a heat pump was an obvious option.

They installed a 16kWh Daikin split-system air source heat pump. This provides underfloor heating to the ground floor of the house, and hot water and radiators to the upstairs bedrooms.

The heat pump has a “very tidy” internal unit that includes the hot water cylinder in a single unit. This is sited in a service cupboard off of their utility room, and the external unit is at the side of the house with a straight-line pipe-run between the two.

Installing a mechanical ventilation with heat recovery unit

The Smith’s home was built to such a standard that it allowed a very minimal amount of air to enter or escape the home (3.06 m3/hr @50pa). This reduced the amount of energy required to heat the home, but it also meant that they needed to install a mechanical ventilation with heat recovery unit. The unit ensures that stale air in the house is exchanged with fresh air from the outside, without losing any heat.

Before deciding on which system and installer to use, Gordon says they did their research by going to self-building trade shows, reading industry magazines, and doing a lot of online research.

Getting financial help from the Scottish Government

The family applied for an interest-free loan from Home Energy Scotland, funded by the Scottish Government, to help cover the cost of the heat pump, solar panels and the battery. Gordon says, “the process was generally painless, and the terms were obviously generous.”

The family received a grant, also funded by the Scottish Government, to pay for the electric vehicle charge point.

Saving money on energy bills

The family has kept an eye on their electricity use so they can compare how much energy they are using now with what they used before. Gordon expects that their annual energy bill will be around 25-30% less than their previous house, even though their new house is around 50% larger and includes regular “top-ups” of their hybrid vehicle.

In addition to saving money on their energy bills, they receive quarterly Renewable Heat Incentive payments for the heat-pump. They expect their total heating, cooking, and lighting bills to be around £25 to £30 each month, on average.

Gordon says that the air source heat pump appears expensive to run in the winter, but that this is balanced out it by being entirely self-sufficient in the summer months. He adds, “if we had gone for a combined gas boiler and heat pump, I think we would potentially be spending even less, although we would have had the extra cost of installing the gas supply”.

Having a “whole package” of the renewables systems together with the app, means they know “exactly what is being used and when.”. Gordon reports that “we are certainly more conscious about our usage than we ever were before and we will use the washing machine when it’s a sunny day, for example, to use the free electricity.”

Feeling the benefits of a cosy, energy efficient home

Gordon says they’re still working out what settings and timings work best with the underfloor heating “as we never had it before. There are certainly no cold spots… and the upstairs bedrooms never seem to need heating at all, even in the winter. We certainly don’t have draughts, which we had a lot of previously in our last house.”

He thinks that if they had stayed in their old home, they may not have spent as much on energy improvements such as solar panels because they wouldn’t have seen as much return on their investment. However, they are glad they made the improvements in their new home, which they also think has definitely increased its property value.

Gordon’s advice: take a fabric-first approach

Gordon’s advice for others building a new house is that “it’s definitely worth spending as much as you can afford on the ‘fabric-first’ approach.

“It’s a lot less expensive to do this at the construction stage, whereas it’s often very difficult to do more once the house is up. You can always replace a kitchen or furniture in the future, but it is very difficult to run new cables and pipes at this point”.

Gordon says that “the electricity used by our heat pump in the absolute depths of winter, on a daily basis, can be very high. When we had an extended cold spell, the monthly bill was significantly more than what we would have spent previously with gas. With hindsight, a hybrid system with a gas boiler would probably have lowered our bills, However, it would only have been for short periods over the year and probably wouldn’t have warranted the additional initial cost, but it might be worth considering.”

However, “when making the investment in a brand-new house, the decision to install the heat pump and the solar panels and so on, was definitely one worth making.”

Feeling inspired?

If you’re thinking about installing renewable technologies, our Home Renewables Selector will help you discover your options and calculate your savings. You can also use the Renewables Installer Finder to find professionals in your area.


Updated June 2021.

Post 2003
Air source heat pump (air to water)Solar PVElectricity storage
Low energy lighting systemsMechanical heat recovery ventilationUnderfloor heating Zonal heating controls

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