Solar Power - Definitely Green but is it affordable

007apm

Solar – What’s in it for us?

Renewable energy clearly helps to prevent further climate change but is it affordable?  We have decided to invest in solar technology and wanted to share our thoughts…

The rise of energy prices

Daily Per kwh Daily Per kwh   Sep-21 23.921 12.549 26.496 2.484 Fixed rate Oct-21 24.01 20.871 24.01 4.055 Price cap Scottish Power April 2022 + 50% 24.01 31.3065 24.01 6.0825 Pundits

Example Bills

These are/were my energy prices in the second half of 2021.  If I do nothing then once the cap is updated in April 2022, pundits are expecting prices to rise by 50% or more which is explored in the last row of the grid. This isn’t the energy suppliers raking it in, but the same may not be true for the energy producers.  World gas prices have risen from circa £60 per Therm in Jan 21 to £420 now (Dec 27th) and electricity from about £100 in January to £320 per MWh in the same period.

Our family comprises of 4 adults living in a large semi-detached house with gas heating, hot water and hob.  Electric ovens, low energy appliances except for an old tumble dryer and the house is well insulated. For us that means that our bills are going up significantly:

	Electric		Gas
	Standing	Fuel	Standing	Fuel	Annual Total	Monthly
Sep-21	£87.31	£677.65	£96.71	£290.63	£1,152.30	£96.02
Oct-21	£87.64	£1,127.03	£87.64	£474.44	£1,776.74	£148.06
Apr-22 TBC	£87.64	£1,690.55	£87.64	£711.65	£2,577.48	£214.79

Please note that the last row may be better or worse and 50% still doesn’t cover the increases in wholesale fuel which makes up about 30-40% of supplier costs.

Is Solar an option?

We are fortunate enough to be able to invest in solar energy and have a house that works for solar; single plane roof in a sensible direction. Our goals are to reduce the energy bill and save a tiny bit of the planet. This stuff is however not cheap and we have begun the journey.  We explored a basic solar option.

EON for example offers a 2.8KW solar only for £4000 and offered interest free credit over 3 years. They suggested that this could generate 2,200 KWh and that we would use 1200Kwh and sell back the remainder on something called a SEG at 5.5p per unit. Work at home during the day perhaps enables us to use more of the power that we generate to create a better return, but at 20p a unit would have saved £360 and pocketed £55 from SEG and so would pay for itself in 10 years..  Adding a battery was expensive (EON + £3000) but probably means that we could use most of what we generated but makes little sense because it would currently take 20 years to pay for the battery which lasts ~10 years.  

Our Solar plan

In our case we have opted for a First 4 Solar system with a 6KW solar with a 7.6KWh battery.  We hope to generate 5,200 KWh per year and USE 80% of the energy produced which we hope will generate a £900 saving at current rates and take 12 years to pay for itself.  Clearly if the price of electric rises a further 50% then whilst costs actually rise, savings are greater and may pay for itself in 8 years.

With Solar	Electric		Gas
	Standing	Fuel	Standing	Fuel	Annual bill	Monthly
Oct-21	£87.64	£258.80	£87.64	£474.44	£908.51	£75.71
Apr-22 TBC	£87.64	£388.20	£87.64	£711.65	£1,275.13	£106.26

I am also considering increasing the battery capacity to 10.2KWh, this would cost £720 extra but it is incredibly difficult to work out whether this is a good investment.  We know what our average electricity usage is, but  I've no idea exactly when we use electricity throughout the day / night to enable an informed choice.

Further scope for battery use

There is a further advantage of batteries.  Suppliers such as Octopus offer a tariff with reduced rates from 00:30 to 04:30. We plan to explore these, prices for off peak energy were as low as 7.5p per KWh.  The idea being that we download the energy when it is cheap and avoid the more expensive day time charge (circa 25p a unit).  There may be other criteria such as having an electric vehicle (it is designed for EVs), hence we may not qualify. This could in theory save a further £155 but may compromise the price cap / dual fuel saving and actually lose money overall.  The ultimate proposition for households with electric cars and/or batteries is to use these as mini power stations so that they actually upload energy to the grid at peak times.  Octopus have a tariff ‘Agile’ that explores this but figures didn’t add up due to the price cap skewing the numbers

Save the Planet?

Regardless of returns, saving over a tonne of C02 each year was a winner with the family. 

Wider Society

It does however point out that the rapid rise in energy costs will hit the poorer members of society for whom £4k for solar is simply unaffordable and the unavoidable doubling of energy bills will force stark choices between food and heating. Those who don't own their own homes are also excluded. 

Conclusion

Hope this is useful?  Due to laws on financial advice, this article tells you what We’ve done and explains my thoughts.  It does not recommend anything other than investigating your own options.  All comments are welcome.

[Evidence links are available but I'm not currently allowed to share them!]

tim_p

I think you might need to elaborate on how you arrive at the ‘use 80%’ figure. 

MWT

007apm said:

In our case we have opted for a First 4 Solar system with a 6KW solar with a 7.6KWh battery.  We hope to generate 5,200 KWh per year and USE 80% of the energy produced...

Your costings suggest you are using 5400kWh a year, or a little under 15kWh a day, it is highly unlikely that you will get anywhere close to 80% self-consumption even with a battery with an array of that size.

Obviously you'll achieve a much better percentage during winter, but that isn't when you'll be producing the majority of that predicted 5200kWh.

Time-shifting from a cheap-rate period will be useful in winter, but without an EV you are blocked from the best tariffs for that.  

[Deleted User]

tim_p said:

I think you might need to elaborate on how you arrive at the ‘use 80%’ figure. 

Indeed, I have a 7kWp array; a 13.5kW Powerwall 2 battery and an 80kW EV. We managed to use 68.2% of the solar output in 2020. I note that the poster makes no mention of the round trip battery loss which for a Powerwall 2 is about 10%. Payback is also in the mind of the beholder. For example, if I used the Ecotricity unit price of 43p/kWh then I am looking at 10 years RoI. That said, all the Grid energy that I use at moment costs me 5p/kWh (but I am guessing that this may not last for long). 

I would also dispute the 10 year battery life. If all batteries stopped working at 10 years then there is going to be a growing mountain of  scrapped EVs from 2025 onwards. The truth is that manufacturers such as BMW have already started using degraded EV batteries as Grid mass storage.

Finally, I would offer a personal opinion on battery size. Yes, batteries are expensive but in my view it is worth paying the extra for a battery that will meet the home’s needs for 24hours along with a good instant discharge rate. The PW2 can provide up to 5kWs. Why so: my total solar output last month was 77kWhs which was 30kWhs below the SolarEdge estimate. On many days, the total daily output was less than 500Whs. Clearly, having a large solar array helps but when on a cloudless cool sunny day the system outputs in excess of 45kWhs a very large chunk of this goes to the Grid: hence, I would question the 80% quoted above.

Coffeekup

I'm interested in renewable energy and have pondered on it for the last few years. However it's so expensive for someone like me on a low income.

So currently I'm trying to reduce/limit my electric and gas usage to reduce the amount of emissions my 2 person household emits.

Electricity emits 0.233 kg of c02per kWh and gas is 0.184 kg per kWh.. according to a few website's.
My average use over last 4 years for electricity is 1,800 per year and gas 9,000 per year in kWh.
So I emit 419kg of c02 for electricity and 1,656kg c02 for gas a year.

Since April last year (21) I've been super on it with turning things like TV/tv box off at the wall, doing fewer washing loads. For gas I've been using boiler less mainly because the price of it these days, it appears warmer (especially this season so far), I also acclimatize to the cold better so only have the heating in only when it's really needed, also using the gas hob better i.e. not simmering for longer and washing hands with cold water (which has helped my eczema considerably).

Looking at my readings if I stay vigilant on my usage and guestimate my next 3 months energy usage. Electricity will come in at 1,400 units of electricity for the year and for gas 5,500 units for the year. Which means 93kg less co2 from electricity and 552kg less co2 from gas, a total of 645 kg less co2 pumped out.

But I wonder if it works like that when it comes to the grid? If every house cut back for a day what would the grid do with the surplus energy they predicted we'd use? Has the co2 been released already because they have generated the power so we may as well just used it in the first place?

I also wonder where I live within a 10-15 mile radius there has been massive amounts of houses being built the last 2 years it's almost unrecognisable, if it's not houses it's horrible looking retail units or ridiculous sized warehouses with no solar panels, green roofing, or somewhere for the water to run off after these fields of tree's and grassland are now concrete causing floods. Shouldn't these buildings be made to have solar/wind generated power these use considerable amounts of power.

I also read an article the other day saying that solar panels need to be recycled better saying most end up in landfill or shredded for parts like silver and the rest scrapped.
Don't even get me started on cars.

So will 1,400 units of electricity usage a year pay off for me  with solar or wind I doubt it unless prices rise considerably.

Reed_Richards

Try posting here: https://forums.moneysavingexpert.com/categories/green-ethical-moneysaving for the largest pool of experts on the forum.

007apm

Thanks for the feedback.  Many factors impact the actual amount generated, I get that and friends advise that Dec21 has been a particularly disappointing month for solar generation in Southern England.  My 80% figure was the hope that if i generate 5MWh in a year then I would be able to use 80% of that.   If it only produces 4MWh then again I want to use 80% of that.  Various references suggest that Summer months produce more than we can sensibly use but it may be that say installing an electric shower and if all of us take morning showers it would move our energy use from gas to self generated electricity and hence put less back to the grid. 

I also note that if you get a 10 year warranty on the batteries then life expectancy is probably 15 years and then it may simply mean that they are not efficient rather than being useless. The solar panels have a 30y guarantee to 87% and so should save a tonne of C02 per year as we approach our 90s!

This is a learning journey and fortunately we can afford to wait for ROI parity; I am grateful for the recommendation to up the battery capacity and will discuss this during the site survey. 

tim_p

Has a salesman told you that 80% self consumption is possible?

markin

I would not do the math based on a unusual 6 months/year, even without the nord stream 2 gas pipeline, gas should settle down after a year or 2, stick with inflation over the long term.

Also going over 3.6KW could take 6 months to get approval from the DNO.

Spies

For my calculations I used 60% self use in the winter months and 36% for spring and summer

80% self usage is unrealistic if you don't have a battery.

Petriix

We managed to use 58.5% of our generation in 2021 with an EV but no home battery. With the Givenergy 8.2 kWh battery we're adding this month, I anticipate getting that above 80%.