lakelandfolk Posted November 23, 2022 Share Posted November 23, 2022 Hello, We have a Solax X1 AC 3.0 Inverter and Solax 12.6kwh batteries. As I understand, although the batteries can hold up to 12.6kwh the inverter will only release that at max of 3.0kwh. If we were to replace the inverter with, a larger circa 6kwh inverter, would that allow us to draw 6kwh to supply a couple of small electric+oil radiators? Would increasing to 6kwh create a problem with the electricity supply company? Our solar panels are rated at 6.2kwh peak Link to comment Share on other sites More sharing options...
Nick Thomas Posted November 23, 2022 Share Posted November 23, 2022 Anything grid-connected above 3.6kW requires a G99 application: https://connections.nationalgrid.co.uk/g99-connection-procedures . It costs to apply, and they may just say no. 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted November 23, 2022 Share Posted November 23, 2022 43 minutes ago, lakelandfolk said: As I understand, although the batteries can hold up to 12.6kwh the inverter will only release that at max of 3.0kwh Right, it is a 12.6 kWh battery and the inverter will draw at 3 kW. So about 4.2 hours at maximum power. A normal electrical heater is about 2 kW, so you could run 1 on full power, and another on half power. Or get some 1 kW ones. Your solar panels are 6.2 kWp. kWh is energy, kW is power. Power is the rate that you use the energy. Link to comment Share on other sites More sharing options...
joth Posted November 23, 2022 Share Posted November 23, 2022 49 minutes ago, Nick Thomas said: Anything grid-connected above 3.6kW requires a G99 application: https://connections.nationalgrid.co.uk/g99-connection-procedures . It costs to apply, and they may just say no. Presumably with 6.2 kWp of solar PV installed a G99 approval has already been issued. What inverter is the PV connected to? Do they have a hybrid / DC coupled option? The solar X battery system mentioned is AC coupled so will definitely need more DNO permission to install that along side the PV, whatever size inverter it uses. Link to comment Share on other sites More sharing options...
lakelandfolk Posted November 23, 2022 Author Share Posted November 23, 2022 Thank you all for explaining the inverter situation. It looks like the max inverter possible would be 3.6 without going for the G99 certificate which we don't want to do. Many thanks again Link to comment Share on other sites More sharing options...
lakelandfolk Posted November 23, 2022 Author Share Posted November 23, 2022 We are trying to source another 6.3kwh battery to add to our system which would increase our total storage capacity to 18.9kwh. Would that require us to obtain a G99 certificate too? Link to comment Share on other sites More sharing options...
SteamyTea Posted November 23, 2022 Share Posted November 23, 2022 39 minutes ago, lakelandfolk said: We are trying to source another 6.3kwh battery to add to our system which would increase our total storage capacity to 18.9kwh. Would that require us to obtain a G99 certificate too? Depends on what is limiting the potential overspill to the grid. Generally speaking your inverter limits the amount of power that comes out our the battery storage. Think of your inverter as a tap, and your batteries as the water cylinder. Small tap, little flow (kW) large tap, bigger flow. The longer either tap is on, the less water is stored, eventually it runs dry, until it is topped up. Link to comment Share on other sites More sharing options...
joth Posted November 23, 2022 Share Posted November 23, 2022 1 hour ago, lakelandfolk said: Thank you all for explaining the inverter situation. It looks like the max inverter possible would be 3.6 without going for the G99 certificate which we don't want to do. Many thanks again I'm confused how your 6.2kW of solar is connected up without having a G99. Note you can't have 3.6kW of solar and also 3.6kW battery inverter without approval. It's the sum of all inverters that must come to less than 3.6, not each one in isolation Link to comment Share on other sites More sharing options...
Marvin Posted November 23, 2022 Share Posted November 23, 2022 Hi @lakelandfolk It might be good to sketch your system. So people can understand the system you have. The devil is in the detail. I think of kW as the power flow rate, and kWh as the amount of power counted. 2kw heater running for 2 hours gives 4kWh used. M Link to comment Share on other sites More sharing options...
SteamyTea Posted November 23, 2022 Share Posted November 23, 2022 (edited) 48 minutes ago, Marvin said: I think of kW as the power flow rate, and kWh as the amount of power counted. No. Power is the Energy flow rate i.e. 1 W per second. A watt is a joule per second, so if you divide that by time, the seconds cancel out and you are left with just the joule, which is the the SI derived unit for energy. There are: 3,600,000 J in a kWh k for 1000 x 1 W [for j/s] x h for hour [for 3,600 seconds]. Edited November 23, 2022 by SteamyTea Link to comment Share on other sites More sharing options...
Dillsue Posted November 23, 2022 Share Posted November 23, 2022 4 hours ago, joth said: I'm confused how your 6.2kW of solar is connected up without having a G99. Note you can't have 3.6kW of solar and also 3.6kW battery inverter without approval. It's the sum of all inverters that must come to less than 3.6, not each one in isolation You can have as much PV installed as you want. The DNO is only interested in what can potentially discharge to the grid which is limited by the inverter. 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted November 23, 2022 Share Posted November 23, 2022 6 hours ago, Nick Thomas said: Anything grid-connected above 3.6kW requires a G99 application: https://connections.nationalgrid.co.uk/g99-connection-procedures . It costs to apply, and they may just say no. They do, sometimes surprisingly, say yes. Always ask Link to comment Share on other sites More sharing options...
Dillsue Posted November 23, 2022 Share Posted November 23, 2022 (edited) 5 hours ago, lakelandfolk said: We are trying to source another 6.3kwh battery to add to our system which would increase our total storage capacity to 18.9kwh. Would that require us to obtain a G99 certificate too? If discharge to the house from your 6.3kwh battery is limited by your 3kw inverter then doubling the battery capacity wont make any difference to the discharge rate of 3kw, if the second battery is connected up in the same way as the first. What's the objection to a G99 application for a bigger inverter? Edited November 23, 2022 by Dillsue Link to comment Share on other sites More sharing options...
S2D2 Posted November 24, 2022 Share Posted November 24, 2022 The £650 application fee for G99 (depending on location) is a big disincentive. OP may have split panels East/West or otherwise not optimally placed which mean gains from upgrading would never pay this (plus the inverter upgrade cost) off. All depends on individual usage, it is a shame a 3.68kW inverter wasn't put in originally though. Link to comment Share on other sites More sharing options...
jack Posted November 24, 2022 Share Posted November 24, 2022 11 hours ago, Nickfromwales said: They do, sometimes surprisingly, say yes. Always ask We were advised to ask for 8.5 kW (the most we could fit on the roof) 7 years ago, and it was granted without question. I was surprised. 1 hour ago, S2D2 said: The £650 application fee for G99 (depending on location) is a big disincentive. Wow, is that typical? I mean, it's been an awfully long time since we applied (mid-2015 I think), but I don't recall paying an application fee. Link to comment Share on other sites More sharing options...
Dillsue Posted November 24, 2022 Share Posted November 24, 2022 SPEN told us informally within a few days we were ok to double export from 16A to 32A. Formal G99 application was £300. Be concious that once youve got approval its unlikely to be withdrawn so youve got the "right" to export for ever. I'm sure it's been said in the past that some DNOs havent charged for a G99 application?? Link to comment Share on other sites More sharing options...
bertybuttface Posted November 29, 2022 Share Posted November 29, 2022 On 23/11/2022 at 14:24, Nick Thomas said: Anything grid-connected above 3.6kW requires a G99 application: https://connections.nationalgrid.co.uk/g99-connection-procedures . It costs to apply, and they may just say no. What if you capped export? Would that still count? Link to comment Share on other sites More sharing options...
Nick Thomas Posted November 29, 2022 Share Posted November 29, 2022 10 hours ago, bertybuttface said: What if you capped export? Would that still count? I think they're interested in what the inverter is capable of, rather than what it's configured to do, but I'm not certain. There's also a G100 scheme which is about capped export, but I've never had occasion to dig into it. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now