How green can you go?

In November 2024, we moved in to our new house. This was the first property that we had bought as we had been renting from a local estate in Monmouthshire since August 1993. In December 2020 I was seriously injured when I was knocked off my bicycle by a drunk driver and our life was turned upside down as I had to stop working, close down my company and plan ahead to life on a fixed income. We were lucky that the driver was insured and we received a reasonable settlement eventually which has allowed us to buy a 4 bedroom dormer bungalow on the edge of the Brecon Beacon National Park with some money left to invest on bringing it up to modern standards and maximise the sustainabilty whilst minimising running costs.

The first step, as seen in the photo above, was to install a comprehensive solar panel system. Our local installer, Green Park Power designed a system for us based around technology from SolarEdge. The 16 panel array generates over 5 kWh on a sunny day and on an overcast day will still charge our 10 kWh battery by lunchtime which gives us enough to cope with cooking, the dishwasher and a load of clothes washing during the day. In Feb 2025, the first month of operating the system, we still managed  to export over 60 kWh of electricity back to the grid to offset the 71 kWh that we used from the grid. February was not a sunny month, neither was it warm so that has left us optimistic about the future and wondering what we can do with all the electricity that we are generating.

After we moved in, it became apparent that the house was losing heat pretty quickly as soon as the central heating switched off. From the pre-purchase survey, it seemed that the cavity wall construction and general level of roof insulation was acceptable but, it turns out, the double glazing was old and could do with being upgraded. This was especially evident when we were subject to the first high wind storm of the season and we could hear the seals around several of the windows at the front of the house were leaking quite noisily. The existing glazing was over 20 years old and didn’t feature the latest developments in glass for energy efficiency.

During the cold of February, we measured our consumption of heating oil at around 10 litres per day which, at a rate of 10 kWh per litre at 100% boiler efficiency, means that we were using about 70 kWh per day as our old boiler was unlikely to be burning oil at more that 70% efficiency.

A substantial amount of the losses will be through the windows so it became apparent that we needed to update our windows and this is scheduled to be undertaken during the middle of March.

Once this is done, we need to undertake a more comprehensive measurement of the thermal efficiency of the property so that we can have accurate figures on which to base the design of our new space heating solution to replace the aging and poluting oil fired boiler.

When we bought the house, it was fitted with an old Worcester oild fired boiler (at least 20 years old and predating their acquisition by Bosch). It still works but is not very efficient and it won’t drive the upstairs radiaters due to the rather ineffective way that the dormer loft conversion was carried out. The radiator system is gravity fed but there is insufficient height differential to enable the upstairs radiators to fill more than the lower third. The boiler also heats the hot water tank.

Something needs to be done…

Our old oil fired boiler heats the water in an insulated hot water tank that is also fitted with an immersion heater and a reasonably sophisticated timer controller so we could use this to heat the water overnight using electricity from the grid on our economy seven tariff of 16p per kWh

If we continue to use the existing system, it would be better to divert power from the solar array once the battery is charged to heat the water, effectively costing us our export rate of 12p per kWh.

Let’s look at the options in more detail…