Grid Tied Solar System Calculator
Notes and FAQ:
- What is a grid tie solar system?
- A grid tie solar system is a solar system (hate writing that twice) that does not have any storage (batteries) and feeds its output directly into the load (house/building) or feeds its output directly into the grid (Eskom).
- Do you have to have permission to install a grid tie solar system.
- Every country and every municipality have their own guidelines for grid tie solar systems.
- In South Africa most municipalities allow for grid tie installations but the way they treat the excess generation is different.
- Cape Town has what is called the Small Scale Embedded Generation (SSEG) scheme. This is the worst scheme in the country as its not really beneficial to domestic class users and removes the viability of domestic class grid tie installations under a certain size. They do have some provisos for basic installation but in a nutshell you will always need to buy more power than you generate in year which sort of defeats the objective.
- Other municipalities do what any other non greedy sane municipality would do and allow an offset of your bill to the value that you generate but will not pay you for excess generation over your usage over a 24 hour time period (for some) and over a monthly period for others.
- Still other municipalities limit the size that you can ever build, in some cases 5kW in others 8kW but apply a generation/offset reduction against monthly bill as above.
- Eskom is now finally accepting grid feed but subject to the size of your supply transformer and limited to your tariff coding. In some instances you may have to upgrade your tariff code or transformer which could significantly impact on the overall financial viability of the system.
- Many many naughty people do connect anyway and do follow the correct guidelines in terms of inverter choices (anti islanding etc) and get reduced bills. Likely they will have to convert over to registered systems when sanity prevails or they municipality catches them.
- Is there a way around this?
- Eskom although given a hard time in the text above does allow (sort of) for a reticulated supply or a lower than use supply. As it turns out some inverter manufacturers luckily have this as a built in function. What it means is that although your inverter is connected to you grid, the inverter will only output to the load and will not export power excess or other back to the grid.
- This also works in most municipalities since in reality you are just lowering your consumption and not utilising their grid as a battery or saving account.
Other useful links:
Off Grid and Bi Directional Solar Calculator
If you have any questions, or would like some additions to this calculator please drop me a mail info@gwstore.co.za