Solar Power - my personal commercial case
Updated: Nov 8, 2021
Author: Phil Clark, Founder of Embedded IT.
In the light of COP26, and as I'm about to get solar power installed, I thought it would be useful to share my personal experience of self-justifying solar power on my home, in the hope that more people consider it. In summary, its not cheap, but it feels like the right thing to do and I genuinely believe it will start adding value to your home soon. Also, you get loads of free electricity.
I have written as a summary, there are loads of facets to consider, but in short I want to give a little background to my home, my energy usage profile, the process I followed to find a supplier (not procurement best practice!), what solution I've chosen to go with, costs and a conclusion. Very happy to take questions / feedback - every day is a school day.
I am not affiliated to any company mentioned below, this is an unbiased overview of my experiences.
I live in a fairly normal 5 bedroom house on the South Coast of the UK.
I have a family of 6 (me/wife, 2 boys aged 12 and 10 (lots of Xbox usage!), and 2 girls aged 24 and 22, who have left home but come home for weekends whenever I can persuade them to)
We have a lot of technology (Computers, Games Consoles, Home Automation), cook with electricity (induction hob, ovens, hot tap etc) and have electric underfloor heating in some of our bathrooms. My only gas appliances power the hot water and central heating
I work from home most days currently, so am always using power during the day.
I bought an electric vehicle in June of this year, have a Zappi 7KW charger and use Octopus Go Faster for my energy provider.
My Energy Profile
As a result of my family situation, we use a lot of electricity and are pretty generally wasteful. Lights are left on frequently (boys...), games consoles are left on frequently (boys....) etc.
My general usage was about 10,000 KWH per annum, with an overnight "base rate" of about 500w when not charging the car. Typical usage is below, 7am spike when we cook brekky, bit of a build around 6pm as we cook dinner, and pop the dishwasher on at 10:00pm
The new news is the EV, which drags 7KWH from the grid between 8:30pm and 01:30am (on the cheap tariff I have), so about 35KWH in total.
Finding a Supplier
My geeky background has meant Solar has appealed to me for years, but I could never quite justify the outlay or time to sort it out.
Earlier this year I decided I was going for it, and was attracted to a "group buy" project that Hampshire County Council was running.
I got a quote as part of this process (around £5k), but when they awarded, they awarded to a non-local supplier who's reviews didn't really fill me with confidence. Because of their process, I only received a standard quote with no real consideration for my setup, which I was worried would end up being more costly once we'd spoken.
I took a recommendation from a friend for a local company and asked them to pop round for a comparative quote. They surveyed my house, using Google Maps initially (below - lighter colours mean more sun), and offered some great advice on different panel placement options. The also opened my eyes to the complexities of inverters (which can make a massive difference to panel performance), and explained how I could integrate the solar with my car to divert excess charge to my car during the day.
Their quote was around £6k, but the difference was the improved inverter, so I have gone with them.
What did I end up buying?
I have bought 10x 385W panels, 1 Solar Edge inverter with optimisers and all associated installation / certification. Total cost was £5,966 incl VAT at 5%.
Panels seem fairly commoditised, so worth picking ones you are happy with the look of. There are some "premium panel" brands out there, but fundamentally they all do the same thing, and not many people will be on your roof checking out the label, so why bother paying top whack?
The inverter is worth understanding. Solar Edge, I am lead to believe, manages the throughput of the panels to ensure any "shaded" panels do not drag down the performance of the other panels when generating. If you don't go with an intelligent inverter, all panels generate at the lowest panel's generation level, so you will not be getting max throughput from your installation. Seemed silly to not spend a bit on getting optimum out of a relatively sizeable investment.
My EV charger is a myenergi Zappi, not the cheapest EV charger you can get, but integrates with your electricity supply and solar to calculate how much energy your house is using, compares that to the solar output, and diverts the excess into your car (in "ECO" mode). Not all EV chargers do this, and although you could get paid for your exported generation to the grid, I can't see the point in that.
I did NOT go for a home battery. The costs for these ranged from £5k-£10k for up to 13KWH, which would keep the house going for a day or so, but I couldn't justify the cost to myself. Also, battery prices are still falling now people are embracing the technology more readily, so I'm gambling that costs will be less in the future and will install then. USD prices for batteries since 1990 below, and can imagine it'll still continue for a while yet.
My commercial justification
If I am using around 1KWH during the day on average when the sun is out (lets say on average 8am to 6pm = 10 hours), then that is costing me about £1.50pd in electricity
My solar will generate between 1KWH and 3KWH once installed, so I'll cover most of my usage during the day and still have a bit to spare (£1.50pd saving - woohoo!)
The excess I'm not using, will charge the car up. It'll never completely charge the car, but lets assume I can divert 10KWH into the car, that'll save me about £1.50pd of over night charging
So £3pd saved, or about £100pm. A £6k outlay will pay for itself in about 5-6 years, assuming the cost of electricity doesn't increase (unlikely), tax on electricity doesn't increase (unlikely).
In reality however, this was never about the cost for me personally. It feels like the right thing to do, its about the same cost that I would have spent on the summer holiday I haven't had for two years because of COVID, and it gives me some energy independence in what is likely to be a turbulent market over the coming years.
Where am I now with it?
It is being installed this week. I hope it all goes ok and my understanding is sound. Will update this when I've had it a few months (through the winter 2021) to see how we're doing.
I am really excited about seeing a graph which shows how much energy my car has taken from the Sun (currently 0% below). The data and graphical representations of home energy usage in some of these installations are brilliant, I intend to bore people rigid with this data over the coming years.
My future plans are now to look at home battery (2022), air source heat pump / some sort of heating replacement (maybe 2022 or 2023 dependent on cost) and maybe a second EV (2023).
Advice for people thinking about it
Get a local provider to come and survey your house (or do it via Google Maps). The modelling and quality of data available will really help with determining if its worth it.
Pick the cheapest panels you are happy with considering the look and performance of them
Ask about the inverter. Understand the options and look at Solar Edge or equivalent
Its not good for everyone. Weird shaped roofs, people in listed houses / sensitive planning areas, houses facing the wrong way etc. Definitely check the likely benefit.
Think hard about batteries right now. They are expensive, and although it means you have clean energy overnight, you'll need a decent sized one to cover all of your overnight usage especially if you do washing / tumble drying / dishwashing over night.
Batteries also don't discharge as quickly as some appliances need. I don't fully understand this, but am lead to believe that firing up your Induction Hob on full pelt, for instance, will be too much of a draw for most batteries and so you'll need to pull from the Grid anyway....
Don't just focus on the "investment". Its important to consider the environmental benefits of your home energy usage. If you aren't on a REGO certified provider, switch to that as a start. But if you want to geek out on how your energy is coming from the Sun, and have graphs to prove it, go nuts on Solar!!!!