The big question is how much should you pay for solar?
Solar energy can be a costly investment, and some providers may charge more than the actual value. This means that you won’t see any savings until you pay off the whole system. In other words, breaking even or getting a return on investment is equivalent to reaching zero.
However, there are some situations where solar energy can pay off in as little as 200 days, but there are also some conditions that affect this outcome.
Grid-tied solar systems can range from a few watts to a few kilowatts, and the bigger the system, the higher the price and the lower the value. A grid-tied system feeds any excess power back to the grid, so you only save what you consume. This implies that you should install a solar system that matches your energy usage.
Let’s take a look at our Deye micro inverter system.
This is a small micro inverter that can provide 800 watts of power. If your smart meter shows that your current power consumption is less than 800W, then this system could suitable for you.
How does it work in real life? Well, it depends on the sun and your usage.
During the day, you consume power. When the sun is out, you produce power, up to 800W. However, if you use more than 800W, or if the solar panels are not producing the maximum power, you will still need to draw from the grid. Just because you have an 800W inverter does not mean you will always get 800W from it.
Let’s say we produce 800W and we use 800W, and it’s sunny and the panels are perfect. You will generate around 6.4 kWh of power a day. That’s about £1.79 in savings. But that’s only in summer. In spring and autumn, you are likely to see around 1.6 kWh of power a day, and even less in winter. You could save around £495 a year with this system.
This is because in summer we have around 8 hours of sunlight, while in spring and autumn we have around 4 hours. If you want the details, each day changes by 3:57 minutes.
lets look at a Growatt Grid tied system.
The difference between this inverter and the micro inverters is the way in which they are used and how they are upgraded. The Growatt is a string inverter, which means that if you add panels they all are in one string. if one is shaded then the whole strings power can be effected.
With the micro inverters, they have a few flavors, the 800W will have two panels, the 1200w four. this means that any panels attached are not effected by the other panel, and you can add inverters and panel sets to upgrade. this is a little different when you add panels to the string inverter, which all have to be facing the same way, yes that means the micro inverters dont..
The Growatt inverters start at 750W, then they have 1kW and 1.5kW, they are built on a single platform and have a PV voltage input of 450v. This means that you could install 10 400 watt panels (4kW) on a 750W inverter which would be a total waste. but you should think about over paneling for winter.
the inverter costs about £100 more.
While small solar works, it can be a little frustrating. You can end up over summer sending power freely to the grid. in our tests we were sending around 60% of the power to the grid.
Now ( March 2024) We are sending a little back to the grid, but we are meeting around 50% of the daytime power needs for most of the day. this being said, we are only running a 500W array on the inverter and its the summer array. ( see angles and panel position post if you want to know more).
Even with the smallest of solar installations the problem comes when you have so much power and you have the option to store that power for later. This entirely changes how your solar installation works for you. Solar can be a “up and down” source of power, so a battery can buffer this so you are using more of the solar power.
The more power you store the more you can save and with this comes some costs.
Not shock here but the battery is one cost and a inverter type known as the hybrid.
There are some ways to lower this cost, but you would pay around £3,000 more.
So you can get your head around this, a 10kWh battery and 3.5kW inverter costs around £3000
Lets do some rough maths. 10Kwh battery holds around 10kWh of power, so we will call that £2.90 a day.
The larger inverter would cover higher load items, like kettles, and ovens, hovers and such.
so you will draw less power from the grid, and of course you would want more panels to charge that battery ( though you can charge from the cheap rate grid)
The battery would pay for the costs in around 4 years.
You could go for a pathway option which would half the cost, but you would not have the same savings from the larger battery, the false economics means that payback would be just over 7 years.
Could you go for a different system that’s low cost?
Yes, you see the costs of a hybrid is in the hoops that they jump to work with the grid, the equivalent non hooper is over £1,300 less in most cases. You could use a Grid Attached. but this is going off topic.
In summary, the best value option for your power use was the Growatt inverter, but the Deye Micro Inverter has recently reduced the price pint by £100, making small solar more appealing. Deye is also known as Sunsynk in Europe just incase youre not familiar with the name.
Solar value does not scale. I have crunched the numbers a lot and found that oversized systems tend to have a longer payback period, even though we are one of the UK’s lowest price hardware suppliers. It is hard to make the systems “good value”.
Based on our analysis, the installation will remain around 80% effective in 10 years and we expect a system to last at least that long, if not longer, averaging about 16 years. Therefore, your payback time should be calculated to be less than half of the life expectancy, so that you can cover both the initial cost and the replacement cost, and also enjoy some extra savings on top of that.
If you think the energy prices will go up, then the return and saving could be greater making it more appealing. but grid attached could be the other option.
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