Old Solar Panels - is it worth getting a battery now?

Exiled_Tyke

Exiled_Tyke said:

This is accounted for with an Internal Rate of Return calculation (IRR). I didn't share this as I thought it would not be of interest. Using my numbers above it is still pretty high (17%).  With the pre-crisis numbers the IRR obviously comes out a lot lower and the investment decision is less clear. 

I plugged some numbers into Excel and my FIT gave a 25-year IRR of 15% or so even without considering the saving in electricity use. I was quite surprised (and want to check my calcs again).

I'm happy to try to crunch the numbers again for you if you want a second opinion. (but I won't claim to being correct)!

QrizB

Exiled_Tyke said:

Exiled_Tyke said:

This is accounted for with an Internal Rate of Return calculation (IRR). I didn't share this as I thought it would not be of interest. Using my numbers above it is still pretty high (17%).  With the pre-crisis numbers the IRR obviously comes out a lot lower and the investment decision is less clear. 

I plugged some numbers into Excel and my FIT gave a 25-year IRR of 15% or so even without considering the saving in electricity use. I was quite surprised (and want to check my calcs again).

I'm happy to try to crunch the numbers again for you if you want a second opinion. (but I won't claim to being correct)!

Here's my data table FYI. Sorry about the (lack of) formatting.

Value	Description
-8,350	Year 0 - purchase price of solar PV system
1,144	Year 1
1,186	Year 2
1,293	Year 3
1,311	Year 4
1,301	Year 5
1,301	Year 6
1,446	Year 7
1,208	Year 8
1,809	Year 9
1,436	Year 10
1,575	Year 11 (partial plus estimate)
733	Year 12 (less £1k for inverter replacement)
1,820	Year 13
1,856	Year 14
1,893	Year 15
1,931	Year 16
1,970	Year 17
2,009	Year 18
2,049	Year 19
2,090	Year 20
2,132	Year 21
2,175	Year 22
2,218	Year 23
1,263	Year 24 (less £1k for inverter replacement)
2,308	Year 25

Notes:

• Commissioned January 2012.
• Year 11 is now, I've generated £1375-worth of electricity and should get another ~£200 by the Q4 FIT meter reading.
• The numbers are FIT payment actuals (to date); I've assumed RPI increases of 10% in Year 12, 5% in Year 13 and 2% thereafter.
  
• I've reduced the income by £1k in years 12 and 24 for inverter replacements. If my current one lasts a couple more years I probably won't need a second before the end of the FIT period.
• Year 5 and 6 were identical, to the nearest pound.
• Year 9 wasn't really that good, it includes Q4 of Year 8 as I missed the cut-off date for my Q4 FIT meter reading.
  

My calculated IRRs:

	Description
1.80%	IRR after seven years (ie. break even)
10.63%	IRR to end of Year 11 (this year)
16.16%	IRR over lifetime of system

Exiled_Tyke

• My calculated IRRs:
  

	Description
1.80%	IRR after seven years (ie. break even)
10.63%	IRR to end of Year 11 (this year)
16.16%	IRR over lifetime of system

Yep. I agree with these figures.   Congratulations on what looks like a good investment!

dinkydo62

BoBoDobie said:

I had my solar fitted in 2014, I have 3.6kW.  I've since heard that you can have batteries to store up energy, is this something that a company could fit to my existing solar panels?  I don't know where to start or even if its worth the cost (or how much the cost would be).  Are there any solar experts on here or can anyone point me to where I can find out more information please.

I had my solar panels fitted in 2017 (3.6Kw the same as yours) and had batteries fitted in September last year. There was no problem at all even though my panels have micro inverters fitted which means I needed a hybrid inverter because my solar generation is converted from DC to AC by the micro inverters and then needs to be converted back to DC to charge the batteries and back to AC to power the house.(or that is the way I understand it). I was very lucky as when I decided to have batteries fitted I changed to a supplier who had a time of use tariff just before everything went crazy. I know it is hard to change suppliers at the moment but try to get a time of use tariff if you do decide to have batteries fitted. (Octopus or GEUK are 2 companies that I know of).