Take control of your solar panel investment by doing this one free and easy thing.
More often than not, the moment a fault on a solar photovoltaic (PV) system reveals itself is when it's time submit the quarterly generation meter reading to your Feed-In-Tariff (FIT) provider. Your FIT payment provider may warn you if your meter submission is lower than expected. This can be really helpful in bringing a solar panel or inverter problem to your attention. Even so, 3 months could pass between solar output stopping and anybody noticing unless somebody is keeping an eye on things. This could leave the system owner a massive £826* out of pocket before repairs begin. Money that may have paid for the repair if the problem was noticed quickly. These out and out system failures are the easy ones to spot. When your solar generation meter doesn't change at all day to day it doesn't take a genious to know something is wrong. When the meter stops flashing and the inverter starts, you know for sure you have a problem. Things aren't always this straightforward. What if the meter keeps flashing away, the panels are generating, but how can you be sure they're working as hard as they should?
What’s the best way to avoid lost solar power generation and keep performance tip top?
The answer is not a solar service contract! In all likelihood your solar inverter will fail at some point during the system lifetime. Unlike a car, it has no user serviceable components. If the fan or ventilation fins are clean, there is nothing in an annual inspection that will predict or prevent an inverter failure, nor prolong it's life. An annual visit from a competent solar technician may pick up performance issues or faults small enough to go undetected by the system owner**, but I would argue that with a little bit more knowledge, you as the system owner will be in a position to spot a problem long before that inspection comes around. In addition to which, paying up front for a long term service contracts is a risk in and of itself. I've talked face to face with customers who have been left high, dry and significantly out of pocket in coming to find that their trusted solar service company is no longer trading. I understand the comfort and assurance that a servicing contract can bring. It feels good to have an expert you trust there for you on the phone when you need them. Save my phone number and save your money. I'm here for you when and if you need me.
More often than not, the moment a fault on a solar photovoltaic (PV) system reveals itself is when it's time submit the quarterly generation meter reading to your Feed-In-Tariff (FIT) provider. Your FIT payment provider may warn you if your meter submission is lower than expected. This can be really helpful in bringing a solar panel or inverter problem to your attention. Even so, 3 months could pass between solar output stopping and anybody noticing unless somebody is keeping an eye on things. This could leave the system owner a massive £826* out of pocket before repairs begin. Money that may have paid for the repair if the problem was noticed quickly. These out and out system failures are the easy ones to spot. When your solar generation meter doesn't change at all day to day it doesn't take a genious to know something is wrong. When the meter stops flashing and the inverter starts, you know for sure you have a problem. Things aren't always this straightforward. What if the meter keeps flashing away, the panels are generating, but how can you be sure they're working as hard as they should?
What’s the best way to avoid lost solar power generation and keep performance tip top?
The answer is not a solar service contract! In all likelihood your solar inverter will fail at some point during the system lifetime. Unlike a car, it has no user serviceable components. If the fan or ventilation fins are clean, there is nothing in an annual inspection that will predict or prevent an inverter failure, nor prolong it's life. An annual visit from a competent solar technician may pick up performance issues or faults small enough to go undetected by the system owner**, but I would argue that with a little bit more knowledge, you as the system owner will be in a position to spot a problem long before that inspection comes around. In addition to which, paying up front for a long term service contracts is a risk in and of itself. I've talked face to face with customers who have been left high, dry and significantly out of pocket in coming to find that their trusted solar service company is no longer trading. I understand the comfort and assurance that a servicing contract can bring. It feels good to have an expert you trust there for you on the phone when you need them. Save my phone number and save your money. I'm here for you when and if you need me.
Knowing whether your solar panels are performing as they should is a simple matter you can manage with a small effort and no additional cost. The answer is simple - you need to know what your solar panels should be generating.
When your solar panels were installed, you were issued with your MCS installation certificate. It’s printed on white paper with a blue border. Look for the figure “Estimated Annual Generation (kWh)”. Knowing what your system is supposed to generate over a year is of limited use in the ongoing appraisal of solar PV performance. We need monthly figures at the very least. Lets sort that out now. The chart and table above show the estimated monthly generation of this 4kW solar PV system, including weekly and daily averages for that month. It also shows the likely probable year to year variation in the estimatesd due to weather. Actual daily generation figures vary wildly against the average so don't get too hung up on them. Make a note of the weather for daily troubleshooting readings to help you make sense of highs and lows. Wet weather or condensation at dawn can trigger intermittent isolation faults that can be tricky for your installer to detect on a dry afternoon so these notes can be revealing. Weekly or monthly readings give a clearer view of system perfomormance for general monitoring purposes. Please feel free to download the spreadsheet here (without having to register, free for personal use only). Input your own annual generation estimate into the red box to get monthly estimates for your system. The printed sheet includes a chart for you to jot down your meter readings. If you don't have solar monitoring to make it automatic, grab a pen and start taking regular weekly or monthly readings. Set a recurring reminder on your phone or write it on the calendar. The more consistent the readings, the easier it will be to compare to the estimates. Taking readings after sunset is best in order to record the full days generation.
Note: you can create your own bespoke pv system estimates from the European commissions Joint Research Project (JRC) website here. You'll need your system power, orientation and inclination. Click on your location on the map to start. If in doubt stick with the default for system losses, these will be lower if a modern high efficiency inverter is installed. You can download the report as a PDF.
What do I do if my solar generation is lower than expected?
Now that you are sure that you have lower than expected generation what exactly should you do about it?
If a tree has grown to gargantuan proportions or a block of flats has gone up next door, obviously, these could be the culprit. It's always possible that the original figures were inaccurate, perhaps shading wasn't accounted for properly in that estimate. The free JRC tool, linked to above, is a quick way to check the figure. Be mindful that your solar panel output is subject to an annual degradation of around 1% as the panels age, but if your readings consistent fall short beyond this, up to around 25%, the most likely explanation is soiling. Dirty panels, general grime, lichen and bird mess can seriously drag a system down. It can be difficult to see from the ground but take a good look to see whether this might be an issue (for any avid twitchers, getting the binoculars out may help get a close look without leaving the ground.) All that's needed to clean them is a stiff plastic bristle brush, water and a little elbow grease. Ask your window cleaner or get somebody local to keep the costs down if you can't get up there yourself. Be very careful not to wash down any panels if they have broken glass!
If a good clean doesn't help and you find you're still down on output, it's time to bring in the experts. From the money you saved on your service contract and minimising generation losses you're hopefully not too grumpy about it.
*This figure was calculated from the generation estimate for this system and comes from the JRC. Export and self consumption were assumed to be 50/50. Feed in tariff and export figures were taken from Ofgen for systems installed before March 2012. Electricity import rates were estimated at 15p/kWh.
**Electrical installation condition reports (EICR's) are typically advised at 10 year from installation for domestic, commercial can vary. Solar is no different. If you want the assurance of a PV electrical installation condition report (PV EICR), carried out by a certified registered electrician with full business insurance, we will be happy to assist.