ᐅ Air-to-Water Heat Pump: Current Consumption and Data

I need to study the subject more thoroughly to still help my father-in-law. He is still focused on achieving maximum self-sufficiency without connecting to the grid and using storage. However, he also knows someone who can provide the equipment at a very low cost...

nordanney schrieb:

No, that’s incorrect.
For self-consumption systems with surplus feed-in (which most rooftop systems likely have), it actually only makes sense to limit to about 7 kW module capacity at south-facing orientation to around 70%.

What else? Anything else would be almost pointless even with a battery. Since mid-February, I’ve been feeding electricity into the grid nearly every day despite having a battery and an electric car.
Now imagine your system being capped for no reason between 11 a.m. and 1 p.m., losing about 3 kWh per hour, every day, over four months (rough estimate since not every day has full sunlight).

You don’t want that just to save 300–400€ once.

Tolentino schrieb:

I still need to study the topic more thoroughly to help my father-in-law out. He is still fixed on the idea of not feeding electricity back into the grid and achieving maximum self-sufficiency with storage. However, he also knows someone who can provide the equipment to him very cheaply...

Instead of just talking, you can run the numbers. Since I wanted to power the heat pump as well, I also calculated cloud solutions. They weren’t cost-effective, or were so marginal that a small change in electricity rates or cloud contract would change everything anyway. Additionally, commercial use—and thus depreciation options—might be at risk.

Systems also behave differently with a small photovoltaic system plus a large battery, or vice versa, with and without a heat pump connected, and so on. That’s why you should calculate, including with or without tax incentives.

Example with a battery: 1 kWh capacity over 15 years at about 220 cycles per year (could be more or less) equals 3300 cycles. If it saves me approximately €0.22/kWh (0.30 – 0.08) with 5% losses, then one kWh should cost a maximum of €726. If it lasts longer (then at 90% and 80% capacity), that’s even better. If electricity prices rise within those 15 years, the payback accelerates. If I can depreciate it, ideally with a solidarity surcharge (which exists), it could even be €1300. So it depends. And nothing should fail during that time.

Deliverer schrieb:

No, storage systems are generally not recommended. They are economically nonsense right now because they are still much too expensive (currently about a factor of 3 away from being profitable) and environmentally bad since their production is complex, and the stored electricity PLUS charging losses PLUS operational losses are not available on the grid to replace coal power.

This could change in 10 years. But at the moment the only reason to have storage is as a hobby.

I agree on the environmental point. But a comprehensive assessment would make sense here.

I don’t see the factor of 3. Where does that come from? With depreciation (see my post about it), 1 kWh should already cost around €1,300 net. More if electricity prices rise or if the device lasts longer than 15 years. After 3,300 cycles, about 90% capacity can still be expected. (For a more detailed analysis see the Eigenwatt YouTube channel).

As a hobby, it’s fun for me (and hardly more expensive than some other hobbies), but it also has the psychological effect that I consistently turn off appliances in the evening or run the dishwasher and washing machine during sunshine hours. So I save a bit through my behavior or possibly extend the lifetime of the devices.

Deliverer schrieb:
(Before someone now brings up a Senec/Sonnen cloud storage brochure: No, their calculations are wrong.)

Right. But most other model calculations are based on an average household. With a heat pump or electric car, the situation is different.

Deliverer schrieb:
BUT: I can reassure anyone who is now disappointed because they wanted storage. Most of you already have one. Many even two. And in a few years it will be three or four.
These are: hot water storage tank, screed, first and second car. You can easily charge about 10 kWh of electricity into the first two. That should be enough for overnight storage. And there are no electric cars with less than 50 kWh anymore.
What the additional 5 to 10 kWh in the basement (for almost as many thousand dollars) are supposed to achieve… I don’t know.

The usually far less than 1 ton of water in the hot water tank (“stores” about 50–60 kWh per month, so roughly 2 kWh/day) is well behind the screed in terms of “capacity.” But I sometimes don’t even need the screed—that is, it’s not available. Also, you only save around €0.12 per kWh that way.

A bidirectionally charging electric vehicle would be the best storage solution for the house. Because for commuting to work, we would need about 1.5–2 kWh per day here.

4lpha0ne schrieb:

Example with battery storage: 1 kWh capacity over 15 years with about 220 cycles per year (can be higher or lower) equals 3300 cycles. This would save me approximately €0.22/kWh (0.30 - 0.08) considering 5% losses,

This calculation ignores that photovoltaic electricity also has a production cost and is not free. You will pay taxes on the stored energy and lose the feed-in tariff if you consume the electricity yourself.

Achieving 220 cycles per year is not easy. It requires a photovoltaic system that can fully recharge the battery on 220 days per year, and consumers who can draw this energy 220 times annually when the photovoltaic system does not supply (enough) power. Additionally, you need a battery with sufficient discharge power to cover these consumers as completely as possible.

There are also minor factors like maintenance charging during winter, which should be included in the calculation.

I roughly calculated this elsewhere—you can search for it—but the result was that one kWh drawn from the battery costs 40 cents or more, which is significantly above the retail price from the grid. It’s more of a hobby!

4lpha0ne schrieb:

As a hobby, I enjoy it (and it’s hardly more expensive than many other hobbies), but it also has the psychological effect that I make sure to turn off devices in the evening or start the dishwasher and washing machine only while the sun is still shining. So, my behavior helps me save some energy or extends the lifespan of the appliances.

I completely agree and even take it a step further. Without a smart meter/inverter/solar panels, most people don’t really know how much electricity their devices consume.

You might notice that after going down to the basement/laundry room every two weeks, the meter shows 200–300 kWh (kilowatt-hours) more, but you don’t often think that the hairdryer uses 1.7 kWh, or that the dishwasher running at 60°C (140°F) for two hours consumes 2.4 kWh—even though it’s rated A+++++.

And when you see the dishwasher using more power than the heat pump, you really reconsider running it in the evening without sunlight.