Solar panel on my roof

Hello,

I have roofs, some of them are on the south. I was wondering if there is a way to save money with solar panel. My undestanding so far is that solar panels are not magic and you can make (some) money if you use your production yourself a lot, because when you sell energy it is for a low price (something like 60% of what you pay for the extra electricity you need).

You will be able to claim it as a deductible expense from a tax perspective, you might even get subventions, and I assume you can maybe get a bigger mortgage. All those advantages don’t seem to make a real difference in my case.

I looked at alternative ways.

  • Group E offers My Sun Contracting https://www.groupe-e.ch/fr/energie/solaire/clients-prives/photovoltaique-my-sun-contracting. They build the solar panels on your roof with their money. You buy the electricity it produces at a low price, but you don’t get cents for the extra electricity it produces. That basically means savings without risk nor investment at the cost of time/meeting and the loss of the possibility to add your own panels on the roof. I won’t sell my buildings so no problem on that side.

  • Romande energie offers to invest in one of their big solar projects https://jardinsolaire.ch/projet if you’re a customer, and you pay your electricity at a cheaper price (the time doesn’t matter :grinning: ) but it looks more expensive because of the network fees (that you don’t pay with your own panels or Groupe E’s panels) and obviously only up to the ammount of solar pannel you invest in. According to their estimation, in 25 years you only save 4.1% of your investment in TOTAL, so it is equivalent to an average savings account (0.2%). Should you use less than what you invested in, you will get the extra cents.

As I was writing this, I realised you can actually use the 2 solutions. For the electricity you use during the sunny days, you get relatively good savings with Sun Contracting, and then for 95% of the electricity you use at night (I assume it make sense to be sure you don’t over-invest) you get the cheapest night electricity. The use of Romande Energie solution doesn’t look more attractive in that case, but that would be the only solution to transform your night consumption into a “savings account” after you max out good savings accounts.

So basically, it seems that the best thing to do is to wait that either the next solar panel generation gets cheaper and/or more efficient or that the subventions gets higher. At that point it will probably make sense to add my own panels. Do you have experience with solar panel ? Did I miss something ? Is the research so slow that it would make sense to have my Sun Contracting for the next 25 years ?

Thanks for the very interesting topic.

When I built my house six years ago, the question of equipping the roof with solar panels came on the table and the architect immediately advised against it, stating bad experience of a previous customer and lack of actual savings. A geothermal heat pump was the best bet in his opinion, because my area has excellent yield.
He said some progress should be possible in the near future with more efficient tech and solar tiles and that I might was to reconsider mid term.

That being said, the offer from goupe-E sounds very interesting… You basically don’t invest anything and buy the current at a reduced rate. The issue is that you are not going to save huge amounts according to their example. 155 CHF are better than nothing I guess, but you may regret that decision over years as solar tech might become more attractive and your roof may not be available anymore for your own investment.

On romande Energie (my current supplier), I checked their jardinsolaire calculator and got the following:

5200 saved after 25 years, for an investment of 5000. More or less 3% if I am not mistaken.

The other option from groupe-E, investing in a solar installation (without battery) with my own funds:

That’s 4.5%. After 16 years, the installation has paid for itself…

@REandSTOCK Can you share your numbers? I guess the point is here, how much time to do you need to reimburse your investment, and how much better solar tech can get during that interval.

First I didn’t make a simultation because we use gaz to heat the water, except in a bathroom, which mean low level of auto-consumption. I have no real taxed income to write off and there is a lot to do in the buildings anyway if I wanted to. I thought that because it doesn’t make sense for a lot of profiles to do it, that the fact that I was not in the best group from a solar panel perspective and at the same time in the best group from an other investments perspective, the return would not be enough in comparison.

I made a quick simulation with groupe E with really approximative numbers and apparently the return would be 6% and I would only need 14 years to get my money back. So it might make sense in the end. I will wait until the PLR realise the subventions will go directly in the owners’ pocket :joy:

my father (has an electric car) decided to look at solar panel for his home in Ticino, orientation south-east (not perfectly south).
all in all with 50% own consumption and 50% resold at 6 cts/kWh, he still has a ROI in 9.5 years. 11 kW on the roof (31 module at 340 W per module) + inverter + all work (key in hand so to speak) is 21’000 chf, and you get 6500 as subsidy so in total 14’500 all included, which is not a lot. And I expect him to have more than 50% own consumption (because of electric car)
Is a no brainer compared to having the money in the bank. The cost of panels and inverter really went down a lot in the last two years.

Interesting topic. I always wondered how much it costs a simple experiments that could give enough power for a laptop and a fridge… The topic is complex…for me.

if you use components designed for 12V car systems than it is actually doable to build a setup yourself.

For instance you could use a 12V fridge and a 12V car adapter charger for your laptop (it is even more efficient because you avoid going to AC current and then back do DC).

If I google this “car fridge” they consume max ~50W in 12 Volt modus. Your laptop charger has a peak as well of 50 kW.

you are rarely using both of them at maximum power, but maybe you like at least 40 W for your laptop in winter (no need for the fridge in winter :wink: ) so since the power output in winter is limited, you may think for something around 80-100 Wp, and of course a 12 Volt battery.
you then charge fro mthe battery (and solar, when available) and the solar panel recharge and keep the battery alive.

I think such “custom setup” are not really at scale for private consumers but it will cost you around 700 chf. You can have 85 Wp panesl with smart battery manager for aorund 500 chf and then 200 chf of 12 batteries + 100 chf of fridge/car adpater etc if not availble. Total ~700, 800 with all adapter.

conrad.ch is a good site with lots of pieces

I was interested because I might show it to some of my friends who lives in almost-tropical regions that get hit from time to time by blackouts. A Battery for a laptop/tv that last a week is a godsend sometimes.

The Fridge is probably not doable since it means buying a new fridge for emergency useage only.

Thanks, I guess he lives in a region with good to very good yield?

The idea is slowly finding its way into my short-term projects, I discussed the subject in my neighbor and he showed a lot of interest (he has a lot of uninvested cash), perhaps we could negotiate a nice price if there are two houses equipping at the same time.

If someone has experience with solar panels (or bad ones), I’d love to hear about it.

yes good to very good, but the roof is not perfectly south. I think right now is the right moment to get them because you have incentive up to 33% of the cost, and the price of panels as fallen dramatically. In a couple of years incentive will no longer be necessary, and they are going to be eliminated.

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If I had a chance to add solar panels I would make sure to get a battery (e.g. Tesla Powerwall), partly because of charging the car and partly to use the energy at night.

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The calculator seems to advise against installing a battery system in my case. They will certainly increase the energy that you can consume for yourself but

  • Battery setup has a strong initial cost and may require maintenance and replacement
  • Your excess of power during the day is not wasted, it can be re-sold
  • You would use your stored current at night, when the rate is at its lowest

That being said, I found an interesting solution that is available in my area (https://www.inera.ch/interieur.php?page=horizon). They offer to take care of the energy storage for you in their dedicated infrastructure against the payment of a per-kw fee. That eliminates the high upfront cost of a battery system.

Can you clarify this? iiuc a Tesla PowerWall should be around 7.2k CHF plus around 2.5k CHF installation.

Funnily enough, I read a lot about panel technology but nothing about inverters and stuff. Right now the main costs are battery and inverters (and all that technology that lies between the panels and the batteries. Also between batteries and your house. If someone “invents” something really cheap on that part of the equation, we’ll see way more panels everywhere.

Based on what I got from the calculator, (8000kw/year of consumption, heat pump, 70m2 of panels), those 10k would add 50% to the base cost and delay the break even point by 10 years. That’s not even considering batteries losing capacity, failing, or requiring replacement in the long run. I doubt that anybody is going to offer 20 years warranty on li-ion tech.

It’s important to keep in mind that extra power produced during the day is not wasted but sold and that makes storage not as attractive as one could think. As a personal note, I expect a lot of progress to be made on battery tech in the coming years. If not necessarily on capacity, on production cost at the very least.

Battery don’t make sense to add right now because for sure, 100%, if you wait a couple of years you will get a much better deal.
They are not incentivized.
Start with panels and wait a couple of years and add either a car with vehicle2grid capabilities or stationary batteries

Maybe you can build your own panels and create a Regroupement dans le cadre de la consommation propre (art. 17 LEne) with your neighbor. Basically, you sign a contract with him, you do the investment + a small aditionnal investment to connect his house. Then he pays you the agreed price, let’s say 17 cts instead of the ~23 cts he is paying. Or of course, you can do it on his roof with his money.

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