Existing House improvements

Front bay windows ground and first floor timber and glass with acrylic sheet magnetic secondary glazing. All rear windows and French doors modern aluminium double glazed. 2nd floor loft conversion and bathroom double glazed velux windows, skylights and French door. Full building regs 2005 insulation on conversion and remaining loft space.
Heating was by a 3 year old Potterton Promax 32 condensing boiler with a pressurised water system off the mains and a 210 litre high pressure Gledhill horizontal hot water tank in the rear loft. All rooms have sufficient radiators to enable efficient heating in winter. Water supplied by 22mm plastic pipe from the street – unmetered.

Installation of solar system

Using GESS of Chelmsford we’ve installed as many solar panels as is possible on the various roofs including the north facing roof over the rear element of the house. All panels are rated at 330 watt. We have 1 south facing panel, 2 east facing panels, 11 panels on the flat roofs facing straight up and 6 panels on the rear roof facing north - a total of 20 panels, max generation 6.6kw. Actual max generation 4.5 kw on sunny summer days, all panels contribute significantly to the overall generation.
The panels are wired up in parallel using Enphase micro-inverters on each panel and the DC current is distributed via an inverter / distribution system using a Sofar ME 3000SP storage inverter to power the house, charge the 9.6kw of batteries and export to the grid.
We have installed 4 X 2.4kw – 9.6 kw Lithium-Ion batteries by Pylontech. These batteries are compact and stackable so can be added to if necessary. They provide a smooth source of power at night time and on cloudy days and are inexpensive.

Installation of Air source Heat Pump

Heat Pump requirements
1. Size – The house has four bedrooms over 3 floors including the loft conversion. Volume calculations stipulated that we would need a pump with a minimum output of 11kw but ideally between 12 and 14kw.
2. Noise - Our pump suppliers, Electric Heat Warehouse of Derby recommended the latest pump from Vaillant – a twin fan 12kw Arotherm Plus. It is Ultra Quiet with very low noise levels 54db is quoted and only 60db when running flat out. Although tall at 1.5m it is not deep, a mere 45cm and would therefore not protrude far into the garden. The pumps positioning was in compliance with all the rules set out for the Renewable Heat incentive and even in mid winter with the pump working hard it cannot be heard from inside our house and certainly is not heard by our neighbour, however we've now discovered that that it falls foul of an old local planning rule that stipulates it should be 1 metre from the fence. I am working with local government and central government to modify this rule as it's implementation rules out heat pumps for any narrow house of which there are millions all over the country.
3. Adaptable for use with existing hot water tank. In an ideal world it would be better to use the specially designed high pressure hot water tank supplied by Vaillant for use with their Arotherm plus pump. However there is nowhere in the house that could accommodate the tank as it doesn’t come in horizontal form like the existing tank. The engineer from electric Heat Warehouse who fitted the system, with advice from Vaillant, was able to solve the problem by fitting a 100 litre buffer tank between the pump and the heat exchanger and the system works extremely well. It means that there is always a large supply of hot water ready to feed into the central heating and hot water tank and the pump itself is not cycling on and off as it would if heating the hot water only via the relatively small heating circuit in our existing hot water tank. On the 16th February 2021 a 12kw Vaillant Arotherm Plus air source heat pump, buffer tank, heat exchanger and control electronics were installed and connected into the existing central heating and hot water pipework. The gas boiler was removed completely thus eliminating a major source of CO2 emissions into the atmosphere.

Latest annual data on the solar system

Between 1st Jan and 31st Dec 2021 the solar panel system generated 3.99 megawatt hours of electricity after conversion. The self use rate went from 90% in the winter to 30% in the summer. Monthly export to the grid is now 8.0p per kwh was 5 - 10 kwh for Nov through March rising to 50kwh in April and Sept, 150kwh in May, 350kwh in June, 400kwh in July and 180kwh in Aug. The solar system largely runs the house for the months April through to end Sept. It is worth noting that for the whole year the south facing panel generated 281kwh, the upwards facing panels averaged 240kwh and the north facing panels averaged 175kwh. This explodes one of the many negative myths around variable facing solar panels. They are all valuable contributors.
The winter months demand a high level of electricity from our green energy supply but the solar panels still contribute a small amount especially on bright cold days

Latest data on the air source heat pump

Heat pump installation was fully functioning by the 16th February 2021. We now have data on a full year electricity usage for the year 1st January '23 to 31st december '23. Please see Octopus energy bar chart. During the summer months of May through to end September the pump is only used to top up heat in the hot water tank for domestic use. The solar chaged batteries largely cover the emersion heater's use of electricity in the very early morning. For the months October through to end April the pump is used to heat the house. The house thermostat is set to 20 degrees C and this temperature was easily maintained throughout the winter even on the few days when the outside temperature was - 3 degrees C. The pump is set to function at 55 degrees C and come on at 6.30 in the morning and turn off at 10.30 at night as we are at home during the day most of the time. At no time could the heating be deemed to be inadequate. Nevertheless as the radiators were 30 years old they were replaced with 20% larger modern radiators in August 23 just to ensure maximum possible heat.

Green energy supplier

We are signed up with Octopus – a green energy supplier that guarantees its sources of power are not from fossil fuels but from renewables - wind, solar, hydro and nuclear. Octopus offer a tariff called Octopus Go that runs from 12.30am to 4.30am at 8.10p per kwh, roughly one third the price of daytime electricity. There are two forms of energy storage in the house – 9.6kw of batteries and a 210 L hot water tank with a 3kw emersion heater. Both of these are switched on to be charged during this early morning window of cheap electricity so the house starts the day fully charged with the hot water tank thermostat set at 62 degrees C. In order to keep Legionaires disease at bay this process is maintained throughout the year for hot water but battery charging is turned off during summer months as the solar panels charge them up during the day.

Investment costs, electricty costs.

Our total billing for electricity supply for 5th June 2021 to 4th June 2022 was £971.92. Our total export earnings were £75.76. Our total gas and electricity bill for 2019 prior to the installation of solar panels, battery and heat pump was £2256. The total cost of installation was £27,000 but we received a £5,000 Green Home Grant from the Government and will receive 90% of the remaining £8,000 from the Renewable Heat Incentive scheme. Electricity has now reduced in price from a max of 42p a kwh in 2023 to 24p a kwh with a cheap early morning rate of 8.10p a kwh. Last year, bills were very high but now that prices have lowered I am confident the savings will be considerable and most important - we are not pumping CO2 into the atmosphere from a gas boiler.