Last Summer I discovered that having an East-West facing roof didn't make solar panels pointless after all, and so we found a company to install them (don't worry Mum - we got three quotes).
Anyway, after a lot of delays we got the system installed three weeks ago.
System capacity
For those interested in the details it is sixteen 395w panels (two strings of 8) with a 5kw inverter and a 9.5kwh battery.
We also had a smart immersion heater installed into our hot water tank. Well, not that smart - it doesn't do solar divert. But that doesn't matter because the battery can make up any difference if there isn't enough solar at the precise moment we are heating the water. The aim here is to stop using gas for half the year.
In the three weeks so far (in March) we have been almost entirely self-sufficient for electricity and hot water.
If you look at our energy usage I don't need to tell you when we had the system commissioned (they have to empty the battery and then fill it all the way to test it), and our first full day of solar.
Even the days when the battery wasn't able to cover all our usage and we briefly drew from the grid (because we had too many appliances on at once or because it was slightly too slow to react), the usage was still lower than the day we were away from home (28th Feb).
This was March - there should be plenty of surplus over the Summer months when days are much longer here in the UK.
FYI - I'm not expecting to cover our usage from November to February, but might get a little extra power, we will see!
Payback period?
I signed up to this in order to reduce our carbon footprint, safe in the knowledge that it would be a good investment given that it would offer a saving on energy bills and that the panels would last at least 25 years (that is the warranty period). The inverter is unlikely to last that long, and the battery will start to degrade eventually, but they will pay themselves back too.
It is hard to work out exactly when the "payback" period would be, because it would involve a lot of assumptions about future energy prices.
The reason why I was very confident that it would be a good investment is because I've been following the climate and energy issues for a few years now and I'm convinced it is necessary to move to net zero (in fact I believe it should happy MUCH more quickly than our government is planning, given the reality and (im)morality of climate change).
Self-use only?
The focus of the sales pitched when I ordered the system was on self-consumption. The idea is that you want to save yourself from importing electricity from the grid, which is expensive.
However, I was keen to get more solar panels than most of the companies thought was sensible because:
- Those of us with suitable rooves should be supplying clean energy to the grid
- Energy prices could rise further
- I want to offset my usage at other times of the year
- I pay for offsets, so this is an extra saving that doesn't get factored in to payback calculations
- As renewables provide more and more of the electricity demand supply and demand will be
Dynamic Pricing
However, since we ordered our system, Octopus Energy (a very forward-thinking company) have introduced a new tariff for people with solar and battery.
This is a relatively dynamic pricing structure in that it varies at different times of the day.
They already had some tariffs with cheap overnight prices (good for a home battery), but these were only available to people with an Electric Car and we haven't (yet) got one of those.
Octopus Flux
The idea behind the new Octopus Flux tariff is that people with a battery can supply the grid during the evening peak period.
The export rate is much higher than the paltry standard amount that focuses everyone on self-consumption.
Now, I don't know if we will max out our battery every evening. Doing so might shorten the life of the battery.
However, we have West-facing panels and I am hoping that they will be generating well into a Summer evening, and that we will be paid handsomely for that. Perhaps a few extra pounds on a sunny day, which would obviously reduce the payback period substantially.
And part of the reason for wanting a battery is to ease the peaks and troughs that we place on the grid. After all, gas is always the source of the marginal (next additional) unit of energy (hence why gas sets the price).
Essentially, in the months between ordering the system and getting it, I think that the expected returns have increased already as a result of this Octopus Flux tariff. We will be receiving several times the export payments I expected when ordering the system. It will pay itself back quicker than I expected.
The Future?
As part of the (absolutely necessary) move to net zero the following will be necessary:
- Much more renewable energy for the electricity system
- Electrification of transport (cars)
- Electrification of heating (heat pumps)
In the future the above logic about marginal use should become more and more relevant, so that pricing better matches supply and demand.
I expect that pricing will be even more dynamic than the Flux tariff. Price will also vary depending on supply of renewables and demand at that time.
So rather than have pre-set times when the electricity is cheaper or more expensive it would vary depending on the amount of wind/water/solar electricity available and the demand of other users.
People with batteries can shift their usage from the high-demand-low-supply times to the high-supply-low-demand times. They can, and should, be paid for doing this.
Essentially, people who don't have batteries will have to pay more for their power, while people with batteries will be able to make use of cheaper prices.
Solar helps with this because you are generating yourself, filling up your battery along the way. Having a battery makes sense with solar, but it also makes sense independently.
Ready for net zero?
Essentially, if you are doing any kind of renovations to your house make sure you:
- add solar panels as a lot of the cost is in the labour involved (the scaffolding, electricians etc.). The panels themselves are pretty cheap (about £200 - £300 each) and will pay themselves back in no time.
- insulate to as high a standard as possible to limit heat loss (electricity might be more expensive when it is very cold as everyone will have their heating on at once)
- prepare for a high-efficiency heating system (a heat pump) by installing a low-flow system - underfloor heating or large radiators
- have an electrical system that can cope with adding things like a heat pump, EV charging and battery in the future (though I was reassured it would be possible to extra things on even though our fuse board is now full).
