Why solar PV?

Firstly, I should say a little about WHY we looked into installing a SolarPV (solar photovoltaic) system in the first place.

In fact, before that I should probably say why we looked into solarPV and did not even consider a Solar/Thermal system (i.e. heating hot water directly from the sun). On the face of it, solar/thermal systems appear to be very attractive. The efficiency is MUCH greater than SolarPV. The reason we did not consider it is simple. We lived in California for a long time, and saw many many solar thermal systems. Almost all of them had been decomissioned. Everyody we knew there who had first-hand experience of such a system had tales of woe involving leaks. In the UK we, personally, know only one household with such a system - and it does not work properly. So, although I am certain that it MUST be possible to install such a system and benefit from it, we decided from the outset that we did not want to go down that route. As the technology continues to mature (and as energy prices rise) it may well become more attractive to us (although our available roof area is now covered with SolarPV so...).

Now, the next thing to consider is that our household in atypical. This will make some aspects of our experience irrelavant to may households. However, some things will be relavent no matter what the similarities or dissimilariteis between households.

We moved into our house in Tattenhoe in autumn 2021. Immediately, there were some things wrong with the property that we had to rectify. Firstly, the hot water tank was fed from an open cold tank in the loft. This meant that the showers were slow and one of them had been fitted with a noisy electric pump which helped a bit, but sounded like a jet engine. We decided right away that we needed to upgrade the system to mains-pressure hot water. We looked at our options and, at the time, the government was offering a generous subsidy for installing heat-pump based heating systems. This meant that we could update the plumbing and remove the gas supply from the house at the same time. Not an approach that would be favoured by everyone - but for us this was a win-win.

VERY broadly speaking, a unit (kWh) of power supplied as electricity is a little more than three times the cost of the same unit supplied in the form of gas. A gas boiler is 70 to 90% efficient (depending on the type of boiler). An Air Source Heat pump (ASHP), because it pumps heat from the environment, is roughly 300% efficient*. This makes an ASHP attractive even with the high cost of electricity compared to gas.

So, the ASHP means that our electricity consumption is much higher than a typical household of a comparable size. This has to be taken into account when looking at our results.

So... by now you can probably see why we were considering SolarPV. Getting rid of the gas and going "all electric" makes SolarPV very attractive. Generating some of our electricity from solar panels means that we can run some of our space-heating and water-heating (the most expensive parts of our energy-consumption) for "free".

* A Ground Source Heat Pump can be something like 500% efficient, but it is a rather expensive thing to install other than in a new-build

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