Solar & Battery install - How much can I save

Will solar & batteries save me money?

Now that I know roughly what size of system I need, it would be good to know if it is going to reduce my energy bills. So I looked at ways to calculate potential savings.

What does my electricity cost just now?

My daily electricity consumption is around 8kwh, that's around 2,920Kwh per year or 243kwh per month. My electricity charges after the price cap lifts will be 49.64 for standing charge and 27.84 per kwh - which makes my annual bill £994 (365 x 49.64p + 2,920 x 27.84p) - and that's before I consider charging my EV at home 😱 

What would a battery only solution do to my electricity bill

A battery only system should allow me to charge the battery off-peak and then use that energy during peak times. There are some limits though

• Whilst I have sized my battery to cover my full days load, the inverter wont allow it to cover the full peak. As such there will be times when the grid is used along side the battery to provide power
• Most off-peak tariffs (like Octopus Go) now require you to have an EV. I have an EV so should be able to get an off-peak rate 🤞

I've estimated that about 10% of the time I will need to draw from the grid alongside the battery. So in simple terms 2,628Kwh (90% of my electricity) could be provided by charging the battery using an off-peak rate and 292kwh (10% of my electricity) would then need to be taken from the grid at peak rate. Using an off-peak tariff like Octopus Go, the standing charge is 24.86p, off-peak kwh charge is 7.5p per kWh and peak kwh charge is 30.83p per kwh. So my estimated annual charge would be around £377 (365 x 24.86p plus 2,628 x 7.5p plus 292 x 30.83) or £31.50 per month

Batteries alone would save me over £600 !!!!

How much electricity will my solar panels generate 

There are some really good web sites out there that will help you calculate how much electricity your solar panels will generate. The one I used is linked below and it will work out how much electricity you will generate each month of the year based upon your location, roof pitch, house orientation and size of solar installed. I've based my calculations on a 5.2kwp system as that's what I've decided to get.

https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP

To use it :

- Select your house location on the map

- Select the “grid connected” tab

- Put in the amount of solar capacity you will have 

- Select "mounting position" as Roof Integrated 

- Put in the roof slope - I have a 45° pitch

- Put in the Azimuth - this is the orientation of your roof relative to due south. East of south is a negative value and west is positive (ie due east is -90° and due west is +90°). I used +25 as my roof is slightly Southwest facing

- Click the “visualise results” button

This estimate (remember its only an estimate) suggested 4,238kwh annually. Obviously that is only going to be when the sun shines, which is not always the case in Scotland and is never the case when its dark 😁. Knowing my monthly consumption was roughly 243kwh its clear that in January, February, November and December its unlikely that solar will meet my needs, however for the other 8 months it should cover most of my needs 🤞 . I say most as just like the battery only system, my system isn't configured to handle the peaks - it will still draw from the grid. So for those 8 months I'll still estimate 10% from the grid. 

So what does this all mean to my bills

Well in the simplest possible terms, if I have a solar and battery system, my solar panels should charge my battery and provide most of my demand for 8 months. For the other 4 months I'll be relying on my battery. 

Given the battery only solution works out at £31.50 per month, that means 4 months at £31.50 totaling £126. 

For the months when solar will provide 90% of my capacity for free, I will still have to pay a standing charge and 10% of my capacity will still need to come from the grid at peak rate - so that's 243 days at 24.86p (8 months standing charge) or roughly £60, and 24.3kwh (10% of my monthly consumption) at 30.83p for 8 months again roughly £60. So my annual electricity bill should be £246.

In addition I will (or should if I fill out the forms properly), get some money back for the excess I generate which goes to the grid through the Smart Export Guarantee (SEG) scheme. Its not a lot as the rates are about 4p per Kwh exported. At a really rough estimate, based upon monthly consumption and monthly generation I expect about 1,500kwh of export in the 8 months when the solar generation exceeds my needs - so I might get back around £60 from SEG. That means my bottom line is an annual electric bill of roughly £186 or £15.50 per month

Batteries and solar should save me over £800 !!!!

So whats the payback period

As my system is costing £9,450 installed, it would take around 12 years to recoup my investment based upon £800 saving per year. 

However I'm not looking at my investment from a "pure return on investment" basis. I am trying to: 

• protect myself from future price increases
• invest in my property rather than putting money into the profits of the big 6

On this last point, it's hard to quantify but a good install of solar and battery will give your house a better Energy Performance Rating and reduce the running costs. As such it will add value to your house. Even if that is only a couple of thousand pounds, it makes the payback period even better.

Next Step: How the system should work 

One final note

If this blog has helped and you go on to installing a solar or battery solution, please let me know by leaving a comment and sharing this page as I really like to know I've been able to help. 

If you're considering a move to Octopus to charge your batteries in the darker months, please consider using my referral link below (click on the Octopus) as it will give each of us £50 off our Octopus bill.