A Journey to Net Zero
April 2025
We moved to Crich in June 2024 and we are loving the beautiful area, fantastic amenities and wonderful people. Prior to moving here we rented a house for over 16 years which meant that I couldn't really indulge my passion to get to "net zero". Although 3 years ago during the pandemic we moved from 2 cars to 1 and took the plunge with a full electric - so we had really taken a first step. We love our electric car and would never go back, but that's another story!
We should loosely define what we mean by 'Net Zero'. As a starting point i) stop burning stuff (in particular gas for our central heating and hot water) and ii) generate as much power as we use (averaged over the year).
As part of our research we identified the following elements of the system:
a) Air Source Heat Pump (ASHP): to provide the heating and hot water
b) Solar Panels (and Inverter): to provide the power generation
c) Battery System (and Inverter): to provide flexibility and resilience
We also identified that the ASHP, due to its large size, would require planning permission, which seems like madness and thankfully this is due to change soon. In addition, to have the most efficient solar panels (ground mounted south facing) would need planning permission (again this requirement will weaken soon apparently). It was turning out to be too complicated to get the planning permission for the ground-mounted solar so we ended up just getting planning permission for the ASHP and changing plans for the solar panels.
We started by installing the Inverter and Battery System in November 2024 - partly because we'd had quite a few short power cuts in the area during our first few months!
This system allowed us to time shift our electricity usage - filling the batteries when the grid was cleanest (and cheapest) overnight, and running the house from the battery during the day.
Our house has 3-phase electricity and so our system is a little out of the ordinary and challenging, but the installation was fairly straightforward taking 3/4 days.
Alas the system was not as straightforward as it should have been and we'll touch on some lessons later!
To 'stop burning stuff' we needed to move from heating the house with gas and instead heat with electricity. Cooking was already all electric so we could then remove gas totally.
The obvious option was a heat pump of some kind and the easiest choice for us is to replace the gas boiler with an air-to-water heat pump linking in to all of the existing infrastructure in the house.
As part of our extensive research into heat pumps we identified Heat Geek as an excellent organisation at the forefront of researching and installing efficient heat pumps.
As part of this they undertook a full house survey (paid for) which took them a full day to do. Thankfully it showed a well insulated house and good heating infrastructure. So whilst a few radiator changes were recommended, we agreed (in the interests of not changing what didn't absolutely need changing) to go ahead with no changes - and we still had a guarantee of 440% efficiency!
We reasoned that paying a little more for a guaranteed efficient system was worth it. Fortunately, the planning permission was fairly painless and was quickly granted.
I'm pleased to report that the system was installed in March 2025 taking a full week including a few days without heating (although they made sure we had hot water via immersion heater!) It was a hugely symbolic day for us when the gas was turned off. In order to avoid the standing charge we've also asked for the meter to be removed and Octopus currently does it for free - this is due to happen at the end of April.
For the solar system we needed to look at location options - installers can help with looking at options/costs etc. The obvious option is the house roof, but our house has two large dormers and many velux windows on the key aspects, making the layout tricky, somewhat messy and quite inefficient. With a good sized garden we then considered a ground mounted solar system offering near-perfect alignment and efficiency, but that requires planning permission. Again this should be easier in a few months, but I'm impatient! So we changed plans and moved to using garden structures and possibly a small portion of the house roof if needed. In March we installed the first phase of the solar on a bespoke greenhouse/potting shed... just over 4 kwp (kilowatts peak) - nowhere near enough for net zero, but a start!
Over the coming months, we plan to add more solar to garden structures - a pergola walkway and a shed. This won't be perfectly positioned so we'll have to review the generation and decide whether more is needed to get to net zero - we will add more if needed!
Of course, there have been some challenges along the way.
- Installing the battery system first and alone allowed us to look carefully at its performance. We have almost a commercial system given the 3-phase nature of the electricity supply, so we expect some extra issues.
We noticed that it wasn't charging/discharging at the level expected - it was only doing c. 10kwh versus expected 13.5kwh - almost like one of the 4 batteries was not working. It took a lot of persistence and about 4 months for the manufacturer to fix the problem with a firmware update.
- We've also noticed that the system has a large overhead of around 6 kwh per day. One lesson we've learned is that inverters need to be working at more than 10% of their capacity to be efficient. Without the solar and heat pump to keep the inverter busy it was only working at about 1% of max! This is an ongoing issue which is being monitored as more load is put onto the system. (I would now be very wary of having only a battery and inverter in a house due to this issue! I'd never come across this issue in my research.)
- Heat Pumps are different from gas boilers - for best efficiency they want to run 'low and slow' - they can now produce high heat, but that's not ideal. So finding the correct settings takes time and patience - don't expect it to heat the house to the thermostat quickly then switch off. The aim is to find the correct settings to get the house to a comfortable temperature and maintain that through gentle input all day. We're still experimenting, but can report a beautifully quiet and efficient system so far.
In summary, we have the following elements in place:
- An Electric Vehicle, which we love
- A Battery system (including an Inverter which will also take the solar inputs);
- A Heat Pump replacing the gas boiler (and the gas connection will soon be removed)
- A solar PV system - phase 1 (4 kwp) done with another 16kwp planned over 2 phases ... and more if required to get to net zero.
As someone who has researched the various elements of energy transition, it's exciting to finally get to experience it in practice. Of course, it won't be without challenges, but the end goal is worth it!
Ian and Jennie
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