ᐅ Photovoltaic System: Self-Consumption Rate with Battery Storage and Additional Questions
Created on: 27 Nov 2015 13:23
T
T21150
Dear forum members,
At the beginning of 2016, I will be retrofitting my house with a photovoltaic system. It will have an east/west orientation with about 3.4 kWp per roof side.
The system will include an inverter with a small integrated LiPo battery with a capacity of 2 kWh.
This project is not driven by economic considerations. Overall, I expect to pay roughly the same amount each month for electricity as I do now without the photovoltaic system—at least.
Rather, it is motivated by my interest in experimentation and the fact that I genuinely enjoy working with exciting technical things. Also, I simply take pleasure in generating part of the electricity I consume (beyond the emissions created during production and installation) in a CO2-neutral (or more CO2-neutral) way.
With the small LiPo battery (I don’t have space for a larger capacity solution), the share of self-consumption rises from a little over 30% (without battery) to about 48%, based on calculations and projections. It never pays off financially due to the additional costs—in my opinion, however, maximizing self-consumption of the generated electricity is worthwhile. Just my personal quirk.
The east-west roof orientation is—not necessarily a disadvantage in my view—especially considering further increasing the self-consumption share. The system will deliver power in the morning, at noon, and in the evening, but overall it won’t be quite as efficient as a system with a purely south-facing orientation.
My questions:
1. Who among you already has a photovoltaic system with a buffer battery and can share your individual self-consumption rate?
2. What experiences have you had with east-west orientation for such systems?
3. What tools and methods do you use to further increase your self-consumption? I personally have somewhat “unusual” (?) ideas, such as simply waiting for a sunny day before running the washing machine, and similar approaches. Does this behavior bring any noticeable results?
4. Overall, how satisfied are you with your decision to install a photovoltaic system?
5. My house consumes less energy than what is currently predicted in the energy performance certificate. That is encouraging, but else nothing special.
However, if you add up the necessary electrical auxiliary energy (heating, circulation pumps, solar pump for the existing thermal solar system, controlled ventilation, etc.), a noticeable amount accumulates over the year. With the current primary energy factor for electricity of 2.4, and also with the upcoming year’s factor (primary energy factor for electricity = 1.8).
In combination with the solar system, recalculating the energy certificate would produce a better value since some auxiliary energy would be supplied by the photovoltaic system/battery. Also, the house would then generally generate a larger share of energy from renewable sources.
What do you think: Is it sensible and worthwhile to have the existing certificate recalculated after installation?
I would appreciate it if you could take the time to share your views and experiences with me. Thank you in advance.
Best regards,
Thorsten
At the beginning of 2016, I will be retrofitting my house with a photovoltaic system. It will have an east/west orientation with about 3.4 kWp per roof side.
The system will include an inverter with a small integrated LiPo battery with a capacity of 2 kWh.
This project is not driven by economic considerations. Overall, I expect to pay roughly the same amount each month for electricity as I do now without the photovoltaic system—at least.
Rather, it is motivated by my interest in experimentation and the fact that I genuinely enjoy working with exciting technical things. Also, I simply take pleasure in generating part of the electricity I consume (beyond the emissions created during production and installation) in a CO2-neutral (or more CO2-neutral) way.
With the small LiPo battery (I don’t have space for a larger capacity solution), the share of self-consumption rises from a little over 30% (without battery) to about 48%, based on calculations and projections. It never pays off financially due to the additional costs—in my opinion, however, maximizing self-consumption of the generated electricity is worthwhile. Just my personal quirk.
The east-west roof orientation is—not necessarily a disadvantage in my view—especially considering further increasing the self-consumption share. The system will deliver power in the morning, at noon, and in the evening, but overall it won’t be quite as efficient as a system with a purely south-facing orientation.
My questions:
1. Who among you already has a photovoltaic system with a buffer battery and can share your individual self-consumption rate?
2. What experiences have you had with east-west orientation for such systems?
3. What tools and methods do you use to further increase your self-consumption? I personally have somewhat “unusual” (?) ideas, such as simply waiting for a sunny day before running the washing machine, and similar approaches. Does this behavior bring any noticeable results?
4. Overall, how satisfied are you with your decision to install a photovoltaic system?
5. My house consumes less energy than what is currently predicted in the energy performance certificate. That is encouraging, but else nothing special.
However, if you add up the necessary electrical auxiliary energy (heating, circulation pumps, solar pump for the existing thermal solar system, controlled ventilation, etc.), a noticeable amount accumulates over the year. With the current primary energy factor for electricity of 2.4, and also with the upcoming year’s factor (primary energy factor for electricity = 1.8).
In combination with the solar system, recalculating the energy certificate would produce a better value since some auxiliary energy would be supplied by the photovoltaic system/battery. Also, the house would then generally generate a larger share of energy from renewable sources.
What do you think: Is it sensible and worthwhile to have the existing certificate recalculated after installation?
I would appreciate it if you could take the time to share your views and experiences with me. Thank you in advance.
Best regards,
Thorsten
We have a photovoltaic system with a purely south-facing orientation but a very shallow roof pitch (25°). It has a capacity of 7.28 kWp. In 2014, we generated 7.13 MWh, and so far this year, 7.2 MWh. The winter months yield less output compared to a steeper roof, but the tilt is perfect for summer. It is relatively ineffective to run appliances during sunshine hours since washing machines and similar devices nowadays consume very little electricity. Other uses with higher electricity consumption have a much bigger impact. For example, we have an electric vehicle (Twizy) and will soon switch our domestic hot water to a heat pump water heater, which will be charged during the day using photovoltaic power. In summer, we use the split air conditioning system to keep the house at 20°C (68°F). Thanks to self-consumption, often above 70% (we have the “soft” limit), cooling during the hottest days is basically free for us. This was especially pleasant during the 38°C (100°F) days this year.
What is important to know is that devices like the dishwasher, washing machine, and oven create load peaks, where a lot of electricity is consumed within minutes, but for the rest of the program almost no power is used. This becomes problematic if a cloud passes by at that moment. It is better to have consumers that use relatively little power but over a longer period. The split air conditioning system consumes about 600 W when running at full capacity. The Twizy charges at 2000 W for about 3 hours. Since on a good summer day our 7200 W (7.2 kWp) photovoltaic system peaks at about 6000 W (the 70% limit is applied only after self-consumption), we have a good load balance. On such a good day, we can generate 45-48 kWh. In winter, it is more in the range of 2-6 kWh.
Summary over 2 years: total consumption is 3000 kWh (including hot water), and we need to buy 1900 kWh. We financed the system fully and pay 110 euros per month, but we receive about 1000 euros per year in feed-in tariffs (14.07 cents/kWh net). That’s a little over 80 euros per month. This leaves a difference of 30 euros. From this, you can factor in the saved utility advance payment, which amounts to 250 euros per year, or about 20 euros per month. That leaves a remaining deficit of 10 euros. However, you still have depreciation and the possibility to shop wholesale (without a business license, but with a VAT ID number!), which saves a lot. There are always coupons, and many items are cheaper than elsewhere. So, I think the system is already profitable, despite the 110 euro monthly payment.
The battery is unfortunately not worthwhile. It might increase self-consumption by about 1000 kWh, which corresponds to only 250 euros minus the lost feed-in tariff income of 140 euros per year, so a “profit” of just 110 euros in electricity cost savings. Against this are the acquisition and installation costs of the battery, as well as conversion losses of 20-30%. If the battery lasts the usual 10 years, it should not cost more than 1000 euros total—including installation—to avoid a loss. But these batteries cost several times that amount. It is better to switch hot water to electric (heat pump water heater). Since we currently use instantaneous water heaters and the heat pump water heater costs only about 600 euros, and reportedly saves 60% of heating costs, I see better chances for cost recovery there.
What is important to know is that devices like the dishwasher, washing machine, and oven create load peaks, where a lot of electricity is consumed within minutes, but for the rest of the program almost no power is used. This becomes problematic if a cloud passes by at that moment. It is better to have consumers that use relatively little power but over a longer period. The split air conditioning system consumes about 600 W when running at full capacity. The Twizy charges at 2000 W for about 3 hours. Since on a good summer day our 7200 W (7.2 kWp) photovoltaic system peaks at about 6000 W (the 70% limit is applied only after self-consumption), we have a good load balance. On such a good day, we can generate 45-48 kWh. In winter, it is more in the range of 2-6 kWh.
Summary over 2 years: total consumption is 3000 kWh (including hot water), and we need to buy 1900 kWh. We financed the system fully and pay 110 euros per month, but we receive about 1000 euros per year in feed-in tariffs (14.07 cents/kWh net). That’s a little over 80 euros per month. This leaves a difference of 30 euros. From this, you can factor in the saved utility advance payment, which amounts to 250 euros per year, or about 20 euros per month. That leaves a remaining deficit of 10 euros. However, you still have depreciation and the possibility to shop wholesale (without a business license, but with a VAT ID number!), which saves a lot. There are always coupons, and many items are cheaper than elsewhere. So, I think the system is already profitable, despite the 110 euro monthly payment.
The battery is unfortunately not worthwhile. It might increase self-consumption by about 1000 kWh, which corresponds to only 250 euros minus the lost feed-in tariff income of 140 euros per year, so a “profit” of just 110 euros in electricity cost savings. Against this are the acquisition and installation costs of the battery, as well as conversion losses of 20-30%. If the battery lasts the usual 10 years, it should not cost more than 1000 euros total—including installation—to avoid a loss. But these batteries cost several times that amount. It is better to switch hot water to electric (heat pump water heater). Since we currently use instantaneous water heaters and the heat pump water heater costs only about 600 euros, and reportedly saves 60% of heating costs, I see better chances for cost recovery there.
N
nordanney4 Dec 2015 07:22You asked about photovoltaic systems with battery storage – this is a question that hardly anyone can answer, as there are very few people with direct experience.
We have a south-east/south-west facing system on the roof with about 7.x kWp – self-consumption from late autumn to spring is almost 100%. In summer, it’s the exact opposite. Overall result: around 30% self-consumption on an annual average. We have already optimized our energy use – working from home, running washing machines, dryers, and dishwashers during the day, etc.
I’m also reluctant to calculate how much the battery helps because it seems too expensive, too new, and unproven to me (how many charge cycles can it actually handle before it breaks down), and so on.
We have a south-east/south-west facing system on the roof with about 7.x kWp – self-consumption from late autumn to spring is almost 100%. In summer, it’s the exact opposite. Overall result: around 30% self-consumption on an annual average. We have already optimized our energy use – working from home, running washing machines, dryers, and dishwashers during the day, etc.
I’m also reluctant to calculate how much the battery helps because it seems too expensive, too new, and unproven to me (how many charge cycles can it actually handle before it breaks down), and so on.
Hello Elina and Nordanney,
Thank you both for your replies. They are very interesting and helpful to me.
Regarding the Twizzy: I think it’s a cool vehicle. I’ve even sat in one before. At some point in the near future, I plan to have either an electric car or a hybrid. That’s why three-phase power is already available outside. It definitely makes sense to have a photovoltaic system then. I agree with you on that.
I still have some household electrical appliances that consume more energy than necessary and could be replaced with newer models. However, the business case is negative for me, so I only replace devices when they break. Therefore, the photovoltaic system will certainly be useful during the day when no one is home, and the refrigerator, freezer chest, and ventilation are running in the house.
At least your generally described experiences correspond quite well with the calculations I have (with and without storage). My heating and hot water systems are brand new, so I will not be changing them now. I also work from home about 2.5 days per week on average.
The battery storage is very small; it only powers the house overnight (ventilation, etc.). The calculated annual output from the buffer is 675 kWh (kilowatt-hours) per year, which is much cheaper compared to a “real” (meaning much larger) buffer, but it doesn’t really pay off. It’s more of a fun project for Thorsten, as the inverter has a built-in battery. The device comes with a 10-year warranty, and the system is operated under a new type of contract, so I don’t have to worry about the battery failing early. If it does fail, it will be replaced without any additional cost to me.
The calculation also suggests I will use about 1400 kWh per year directly and therefore need to purchase around 2000 kWh from the grid. The self-sufficiency level without a battery is about 30%, increasing to approximately 50% with one. I’m very curious to see how things will actually turn out later. Such calculations are nice, but we’ll see.
As mentioned, our roof has an east-west orientation, with panels on both sides. This means electricity can be “harvested” in the morning and afternoon, while during midday the output from both sides combines (partially). The thermal solar collector is on the east side, where energy supply ends at the latest around 2:30 pm in summer (the maximum daily yield was once 14.5 kWh per day, enough for those days since no one needs large amounts of hot water then).
Best regards,
Thorsten
Thank you both for your replies. They are very interesting and helpful to me.
Regarding the Twizzy: I think it’s a cool vehicle. I’ve even sat in one before. At some point in the near future, I plan to have either an electric car or a hybrid. That’s why three-phase power is already available outside. It definitely makes sense to have a photovoltaic system then. I agree with you on that.
I still have some household electrical appliances that consume more energy than necessary and could be replaced with newer models. However, the business case is negative for me, so I only replace devices when they break. Therefore, the photovoltaic system will certainly be useful during the day when no one is home, and the refrigerator, freezer chest, and ventilation are running in the house.
At least your generally described experiences correspond quite well with the calculations I have (with and without storage). My heating and hot water systems are brand new, so I will not be changing them now. I also work from home about 2.5 days per week on average.
The battery storage is very small; it only powers the house overnight (ventilation, etc.). The calculated annual output from the buffer is 675 kWh (kilowatt-hours) per year, which is much cheaper compared to a “real” (meaning much larger) buffer, but it doesn’t really pay off. It’s more of a fun project for Thorsten, as the inverter has a built-in battery. The device comes with a 10-year warranty, and the system is operated under a new type of contract, so I don’t have to worry about the battery failing early. If it does fail, it will be replaced without any additional cost to me.
The calculation also suggests I will use about 1400 kWh per year directly and therefore need to purchase around 2000 kWh from the grid. The self-sufficiency level without a battery is about 30%, increasing to approximately 50% with one. I’m very curious to see how things will actually turn out later. Such calculations are nice, but we’ll see.
As mentioned, our roof has an east-west orientation, with panels on both sides. This means electricity can be “harvested” in the morning and afternoon, while during midday the output from both sides combines (partially). The thermal solar collector is on the east side, where energy supply ends at the latest around 2:30 pm in summer (the maximum daily yield was once 14.5 kWh per day, enough for those days since no one needs large amounts of hot water then).
Best regards,
Thorsten
May I ask how much the inverter with battery cost? Our inverter will hopefully last a few more years, but eventually it will need to be replaced, and I could imagine installing a battery at that point, since prices will likely continue to fall.
The battery for the Schnuffzi (that’s what we call it 😉 ) costs 40 euros per month for rent, which is quite a sum, and you even need full coverage insurance because the battery must be insured separately. I think I once read that the battery is more expensive than the rest of the little vehicle...
The small one, however, doesn’t require three-phase power; it can be charged from any standard household outlet. A Zoe is planned for the future, though, and I’m already excited about the technology.
Solar thermal systems actually work better when installed on the facade (vertical exposure in winter, which can be useful, and a very shallow angle in summer to avoid overheating). We considered it as well, but the costs did not justify the benefits, especially since the heat pump for domestic hot water is only 699 euros. I’m curious to see how much electricity consumption decreases when hot water is no longer heated by the electric instantaneous heater.
Oh, and something else I really like: I installed an S0 meter (just under 45 euros) for the photovoltaic system. This way, I can see at any time how much electricity the devices are currently using—I find it quite interesting to watch in real time. It gives you the consumption profile throughout the day. I can only recommend it!
The battery for the Schnuffzi (that’s what we call it 😉 ) costs 40 euros per month for rent, which is quite a sum, and you even need full coverage insurance because the battery must be insured separately. I think I once read that the battery is more expensive than the rest of the little vehicle...
The small one, however, doesn’t require three-phase power; it can be charged from any standard household outlet. A Zoe is planned for the future, though, and I’m already excited about the technology.
Solar thermal systems actually work better when installed on the facade (vertical exposure in winter, which can be useful, and a very shallow angle in summer to avoid overheating). We considered it as well, but the costs did not justify the benefits, especially since the heat pump for domestic hot water is only 699 euros. I’m curious to see how much electricity consumption decreases when hot water is no longer heated by the electric instantaneous heater.
Oh, and something else I really like: I installed an S0 meter (just under 45 euros) for the photovoltaic system. This way, I can see at any time how much electricity the devices are currently using—I find it quite interesting to watch in real time. It gives you the consumption profile throughout the day. I can only recommend it!
Hi!
The prices for inverters, including those with batteries, are dropping.
I won't be purchasing the system myself – a different operational model will be used in my case.
The inverter – name and type gladly via private message – currently costs around 4,000 euros (about 4,000 USD). Compared to a year ago, that's already more than 1,000 euros (about 1,000 USD) less. Roughly speaking, the inverter with battery currently costs about 3,000 euros (about 3,000 USD) more than an inverter without a battery.
About the S0 meter: Could you please explain to me via private message what it is? I don’t want to derail the thread here with off-topic posts. Thanks.
Best regards,
Thorsten
The prices for inverters, including those with batteries, are dropping.
I won't be purchasing the system myself – a different operational model will be used in my case.
The inverter – name and type gladly via private message – currently costs around 4,000 euros (about 4,000 USD). Compared to a year ago, that's already more than 1,000 euros (about 1,000 USD) less. Roughly speaking, the inverter with battery currently costs about 3,000 euros (about 3,000 USD) more than an inverter without a battery.
About the S0 meter: Could you please explain to me via private message what it is? I don’t want to derail the thread here with off-topic posts. Thanks.
Best regards,
Thorsten
I analyzed last year and arrived at one expected and one surprising/remarkable result:
Self-consumption 2015 (ratio of photovoltaic production to self-consumption): 20.36% (the already known figure)
Self-consumption 2015 (ratio of total household electricity consumption to self-consumption): 70.16%
(Calculation: (purchased electricity + self-consumption) vs. self-consumption)
I’m really amazed. I had never considered this ratio before.
Oh, and no—we don’t have batteries.
Self-consumption 2015 (ratio of photovoltaic production to self-consumption): 20.36% (the already known figure)
Self-consumption 2015 (ratio of total household electricity consumption to self-consumption): 70.16%
(Calculation: (purchased electricity + self-consumption) vs. self-consumption)
I’m really amazed. I had never considered this ratio before.
Oh, and no—we don’t have batteries.
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