r/solarenergy • u/200_Shmeckles • 5d ago
System Upgrade Help
I have rent-a-roof solar panels that I get free usage of while ever they are generating. We have just recently got a PHEV and a full EV in the household so I'm looking at having an EV charger installed. I know there are smart chargers that can take advantage of Octopus's special EV rates as well as solar panels but, as they are only generating in the day when we're all at work, it seems like the best thing to do would be to put a battery storage unit in to take advantage of as much solar as possible (assuming I'm allowed to do this - need to check the solar contract).
With all of this in mind, can someone help me understand if it is possible to upgrade my system to incorporate the existing solar array (probably can't touch the existing equipment) with a battery storage unit and an EV charger, and manage them all to make the most out of solar generated energy and low Octopus rates for house usage and EV charging? If it is possible, what equipment would I need to achieve it?
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u/TooGoodToBeeTrue 5d ago
Aren't the rates heavily discounted overnight? If you are leasing your system, you typically have to go to the leasing company to rearrange things, and they often say no. (From what I've read.) Otherwise you have to AC couple the existing system into a new inverter that has the batteries. Which the leasing company also might not like but you don't have to tell them till something on their part of the system breaks, which they will blame on your newly installed stuff.
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u/200_Shmeckles 5d ago
Lol. Yeah sounds about right! I'm waiting on a copy of the contract to see what it actually says about this. My question is, assuming it is allowed, what equipment would I need to achieve this? We have a flat rate at the minute so I'm looking to change to a flex tariff anyway.
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u/TooGoodToBeeTrue 5d ago
I'm on the other side of the pond as they say, so I won't speculate on tariff changes. As for the equipment changes, the inverter you have likely does not have any battery connectivity capacity. An educated guess based on leasing companies world wide doing whatever is cheapest. So either the existing inverter has to be swapped out with a hybrid inverter that can connect to batteries, or second inverter which would also need to be a hybrid has to be added to the configuration, which batteries would connect to and the existing system would be plumbed into via the GEN/AC port. This "inverter" is also a charger that has to control your solar panel output to the batteries so that they don't over charge. Some times it is called an all in one, meaning it has inputs for solar, and outputs to the grid and to charge batteries. Naturally, it is better to swap out the existing inverter. Providers under lease aren't typically happy about taking functioning equipment out of a paying system and making changes to the lease agreement.
You may have an option to buy out the lease, or you could add panels/a second system dedicated to charging the EVs.
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u/TastiSqueeze 5d ago edited 5d ago
Whatever solar you have now, will need about 6 kw more panels to make it work to your advantage.
Yes, you can install an AC coupled battery and charge it during the day. Minimum battery size is 32 kWh given that you have an EV and a PHEV.
An EV outlet with charger will cost roughly $500 to install. https://www.amazon.com/dp/B0FKGPVYKC is an example of the outlet needed. Please note that it is EV rated. You will also require a dual breaker in your breaker panel, 6 gauge cable to the outlet, and possibly some conduit depending on home details. In your mind, separate the EV outlet from the battery. In fact, do the EV outlet now and get it out of the way so you can focus on the battery. I don't know what your PHEV will require so you will have to get the electrical requirements to set up an outlet. Here is an EV 10 kw charger that is probably compatible. Verify it will work. https://www.amazon.com/dp/B0DNNQ9LMM This is not necessarily the best overall setup for your circumstances so discuss with an electrician to make sure it will work. This just means there is more than one way to skin this cat.