Understanding Solar Energy

So blindly converting a gas water heater to electric will roughly quadruple your water heating cost.

I've got a heat pump, and I'm in Germany.

Also, if you're in Germany, you can get a balcony PV system from half the supermarkets a few hundred euros, and those are designed to be installed DIY without needing an electrician. Limited power, sure, but way cheaper than €0.39/kWh delivered:

• https://www.lidl.de/p/vale-balkonkraftwerk-ecoflow-820-w-800...

• https://www.kaufland.de/product/502015379/?search_value=balk...

That's still about six times the cost of wholesale low-cost solar panels: https://www.solarserver.de/photovoltaik-preis-pv-modul-preis...

64 watts is about 40–50 liters per day of hot water heated resistively, presumably closer to 150 liters per day with a heat pump. But it seems like the heat pump is only saving you the 700€ for two more such balcony systems, assuming you have the space. Moreover, you don't need a microinverter for a resistive heater.

I'm not sure if you're allowed to just resistively dump an off-grid PV system into a resistive heating system, but I guess if you did, you could indeed save on the cost of the inverter.

my PV system is paid after 6 years of use. if i use current prices for energy. last two years market/spot prices were even higher than that. so in reality it was paid even sooner.

and pv system does not disappear as soon as it is paid, it continues to work. so i have next 4-10 years remaining of lifetime of a inverter.

so for next 4-10 years i am having 100% REALLY REALLY FREE hot water, again for 80% of time... etc vis original comment.

when inverter ends its life in next 4-10 years then i will buy new one, without changing panels. so payback time will be even quicker.

calculations/models of biggest engineers, experts, etc. do not involve thinking about using pv system after it is paid... ( not insult, just exposing state of things )

Also, if you are heating with solar you could heat water directly. But that path is also only available to house owners.

Now that the sun is out for longer periods each day we are "wasting" energy to the grid a lot. I don't really see how to capture that energy though.

1. Buying a battery quickly shifts the break even points to decades. Without a battery I estimate 3-4 years. 2. I would love to heat water, but renting a place limits my options a lot. I was looking at electrical boilers to supplement the gas heater. But we are limited on space for small heaters below the sink and big heaters in the main water path. (Also we can't change the plumbing for legal reasons.) 3. The next best thing is some imaginary insulated water heating kettle that I can control to only use exactly the excess energy. No idea if such a thing exists.

solar PV is order of magnitude cheaper in small systems (per actual provided output per year, not just rated wattage)

AND because hot water energy needs are much higher than for example tv, notebook etc, so after your hot water is heated, you can charge your devices with it, you can not do that with solar thermal. so if people size their systems for winter sunny day, they will have excess in summer so you can use that for other things like bikes, lawnmowers ...

of course there is ratio of people living in blocks of flats / townhouses and people living in family houses / rural, so every situation is unique. so townhouses should be connected to central heating network and heating network provider should chase efficiencies of scale, that is better, faster, cheaper for everyone ( europe / germany context ) if urban density does not allow otherwise.

similar situation with electric cars, a lot of people is crying that there are not enough chargers for them, those are "city" people, but in reality most people live in rural setting or family houses and in germany every house already has more than enough electrical capacity to charge from outlet, you can charge car from 2.5kW which is same wattage as most electric kettles. yes it charges over night (10 hours) only 100 km but every house can do that already. faster charger can be bought. of course situation in cities is quite different, you can not just put extension cord from window. which is feasible in rural setting / family houses. even in berlin roughly 50 % of people do not live in townhouses / high rises.

which is higher latitude than 99.99999999% of USA or 80% of canada population

then it will work even in USA too.

Again read my first post, it is NOT about reaching 100% offgrid which is expensive, and nonsensical for most people

it is about reaching 100% offgrid for 80 % of time and 10-99% offgrid 20 % of time. Which is so cheap in europe that youre generating totally free energy after 6-7 years PV system paid for itself.

Consider running the dishwasher (if you have one) or washing machine / dryer (if you don't dry that in the sun directly) during the day.

Granted, we work from home _a lot_ and also have an EV so it's a lot easier to do load shifting for us, but just shifting the dishwasher and washing machine to 'sunlight hours' already made a pretty decent difference.

E.g. our washing machine uses 1000W over a prolonged period of time which would be perfect to run on a sunny day. But it does so by switching the 2000W heating element so it averages to 1000W ...

So we repeatedly export 800W (without any form of reimbursement) and import the missing 1200W back.

And that is the case for all of our appliances. (I have a sensor to monitor that)

Don't know if more modern machines are better in this regard, our machines are about 5 years old now.

edit: I don't want to sound bitter about it. The Balkonkraftwerk works perfectly fine to power our base energy load.