Retrofit #2: Preparation

TL;DR – do your research, get multiple quotes, go with the one you trust most, prepare the ground for installation.

Finding information

One of the key things when starting a retrofit project (in my mind anyway) is to do some research on what the options are. Before settling on the system we have (which I’ll detail a bit more in my next post) we looked at all sorts of solutions, including thermal infra red panels, electric boilers, heat stones, phase change systems and umpteen battery types. If you are considering an energy retrofit then I recommend you also search as widely as possible. One of the major issues for me was being able to understand what the day-to-day operation of the heat pump and battery might be like – there’s loads of info on what heat pumps are, but much less on what it’s like to live with and operate them. The same goes for batteries – we all pretty much know what a battery does – but what’s it like living with one?

In this section I want to highlight just some of the sources of information that we’ve used to help us decide what system to go with. (I’ve been interested in eco retrofits for years and have read and watched widely, so his is just a relatively short list).


If you want to check how much solar potential your roof/property has then check out the spatial modelling tools in the PVGIS from the JRC. This is really useful, especially if you use a compass, or Google Earth, to work out your roof orientation and size. The values are modelled averages but give a reasonable first pass.

The charts in the following video are also interesting, demonstrating that the larger the array, the more solar generated electricity is available at the start and end of the days, despite missing out on the peak due to inverter regulations. This was a bit of an ‘aha’ moment for me.


The following videos helped us make a decision regarding the battery (although we’ve been wanting one for ages so, for us, these were the final justification than the only pieces of convincing info):

Heat pump

When we first started looking into heat pumps we wanted to know what it was like to own one, not really how they work. At the time it was really hard to find examples of usage on the internet – it was mainly sales videos explaining that they are a fridge in reverse.

One of the first sites to really provide helpful information was the My Home Farm YouTube channel. A selected video is presented here but if you are interested then go look through their archive – there are loads of useful pointers in there.

Recently the folks at My Home Farm have started the Renewable Heating Hub, and the forums on that site are a gold nugget of information – real discussions, with real people about real installations. Brilliant!

A lot of our information has come from the Ecobubl YouTube channel – there’s some great stuff in there!

If audio or Twitter are more your thing then the Betatalk podcast is pretty comprehensive, and it often brings in the practical perspective of installers and people who have worked in the space heating arena for some time. Some of the Twitter threads are really informative.

There are also some great videos in this channel by Tom Bray, where he discusses the practicalities of heat pumps.

Another Tom has a nice blog about living with a heat pump.

If you want to learn a lot about heat and heat pumps, then Trystan Lea is someone worth following! His website is a little out of date but has a load of statistics and information, and the following video is a good watch too:

If building energy modelling is more your thing, or you want to understand your heat loss calculations then you need to go grab a cuppa and look through this sub-site from OpenEnergyMon.

Mixergy, Zappi and EV

We already have experience of the Mixergy cylinder and the Zappi car charger (when used with solar panels), and wanted to have these products again in our new home. We have a Nissan Leaf 40kWh which we are not planning on changing (although I’d love a Honda-E but with the range of a Tesla Model S), and looking forward to charging it from the PV panels via the Zappi when installed.

Speak to others

One of the things that we wanted to do was actually see a heat pump, having never been up close to a domestic one. We posted on Nextdoor whether anyone knew of someone who might let us have a look and we ended up having some great conversations.

One person had a 7 year old ASHP and had lived with ASHPs for 15 years in Scandinavia and another person had a new Daikin installed this summer and had worked as a heating engineer. Both had loads of information to pass on, but the things that struck me most were:

  • The temperature it is commissioned at (e.g. 21C) can be subsequently changed to set the desired room air temperature. I might be a bit confused here, but I think both systems were set up to heat at 21C but both users set their thermostats at below 20C. I was originally under the impression that the heating would run at the commissioned temperature and it would be wrong to set it cooler, but that may have been my making up problems where none exist.
  • Generally, aside from not constantly turning the units on and off, just use the system as you would a normal heating system i.e. either set a timer and/or a desired temperature. 
  • The compressor from older systems is inside the house and can produce a bit of a background hum, whereas newer models (at least the ones we’ve seen) have a compressor in the unit located outside and are pretty quiet.
  • Try and install the outside unit on a sunny wall as the heat from the sun can be used to warm up the unit, reducing the need for the fan to turn on and thus reducing possible noise.  
  • Tinker with radiator TRVs to begin with, to get each room how warm you want them and then leave them alone.
  • Make sure a powerflush is part of the install, particularly if you have fairly old (or microbore) piping.
  • Daikin came across very positively both in terms of their units but also after sales care too.
  • Make sure your insulation is tippety-top for the best efficiency. While the systems still work if insulation still needs to be topped up, more energy will be used, and more energy = more cost.
  • Everyone we spoke to spoke positively about using heat pumps. 


The usual advice applies here: get more than a couple of quotes. We got four, although one was for the solar only. To be honest, the main limiter is whether or not there are enough installers in/near your area that you trust to do the job – getting recommendations is key! Also, make sure that the installers are registered with the relevant bodies – if getting a heat pump you should make sure the installer is MCS registered.

The variation in the prices between the quotes wasn’t huge, so we felt that everyone knew what they were talking about and weren’t trying to rip us off. The quality of the four quotes was different through. One did the heat loss calculations based on values I supplied without visiting, one person who turned up was pure sales and couldn’t answer simple questions about the system (that we already knew the answer to), and two were pretty brilliant.

These two brilliant companies both sent competent engineers to the property; both looked at the roof, garage and heating system; both took measurements and photos; both split their quotes so we could understand pretty much what we were paying for (one of the other two just gave a single lump sum); each recommended different systems but explained why; and both answered our (many!) questions.

Site preparation

Once we had decided who to go with, a further ‘technical’ visit was set up where the senior engineers came to assess the site and confirm a final design. This was useful in understanding how and where various components will be installed.

Before the installation can progress I was asked to organise/undertake some trenching for the water pipes and the electric cables. This will connect the outside unit of the heat pump with the house, and the solar panels on the house with the battery in the garage.

The battery will require a connection to the home WiFi: I’m not sure if it’ll be needed, but I’ve set up an extender (as I already had a spare Netgear unit).

Phew! That was a long post. In my next post I’ll lay out a bit more about the components of the system.


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