Hi all, not sure if this is the right forum, but seems like the right place. I’m trying to go as off grid as possible on the farm property. I bought a generator last year snd waiting to install. I’vd always planned to install solar as I have a large south facing roofline. And the trusses are built up to handle the weight. I just started researching storage including the Powerwall by Tesla. And it dawned on me that these systems could make the generator redundant. I could always sell the generator, maybe for more than I paid. But before doing so would like to hear any ideas or advice on going solar with battery for my backup power. FWIW, selling back into the grid is not very lucrative at the moment.
If you are thinking of dropping the grid connection, it might be a good idea to keep the generator as a back up for the solar. Sort of like not keeping all your eggs in one basket
If you already have a grid connection then batteries rarely make any sense financially. You would need a fairly large battery bank and solar array to even try to make it a couple days. Adding the ability to charge batteries, convert from DC to ac, and connection to grid at least doubles the install price compared to a straight grid tie system with no batteries. I typically recommend enough solar to offset most of your usage but not all. One typically has a meter and connection minimum cost which can not be offset. Sometimes there is a small unit of energy covered by the minimum cost. You might as well use it because you pay for it. A generator will work in the winter for more than a day or two. Battery backup rarely is sized to last a while day with full house load. Tesla power walls will last about 12-15 hours before being depleted at a load level below whole house. Many people install 2x the units to get 24 hours or 12 hours with more comfort. I don't recommend a whole house full load generator. You can save substantial amounts of money by only sizing to run essentials. I haven't run the numbers in a few years. When I was in college I took a course on renewable energy and we had to calculate pv array, battery storage, and generator capacity for several locations. Even in the forest of Costa Rica a generator and pv panels was better than batteries. The site was an eco-tourist spot so batteries were selected so no generator noise was present when the customers were onsite from evening to next morning. When customers were gone the generator could be used to make up power and charge battery banks. For the next night.
I also agree that a battery bank is not worth it if you have the generator. I'm sure the rules vary by region, but we are allowed a PV array that is sized at 120 percent of usage and instead of selling back the excess we bank credits for the cloudy months. So far we just pay the $26 monthly fee to be grid tied.
I do have a grid connection. Here in Ontario, whatever you produce gets sold into the grid as a credit against your bill. Credits expire in 12 month And the system can be as much as 500kw. i gues I will proceed on panels + generator. Can always look into storage down the road.
We have a Tesla Powerwall as backup power for our grid tied array, we are not off grid. The added expense of batteries and array size, especially in the northern latitudes, to be be off grid when you have the option to be grid tied is not worth it unless you value the ability to power you home in the event of some prolonged catastrophic grid failure. You could downsize the array and add a generator as a second power source for the low solar production months, but that has added expense both for the interconnectivity of the generator with the batteries/array and the production (fuel) of the electricity from the generator and it kind of defeats the point because you are still dependent on fossil fuel. Grid tied with net metering is the best option from an economics standpoint. You may find that property insurance can be difficult to obtain and more expensive for an off grid set up. If you have a mortgage there is likely some fine print that requires you to maintain a grid connection, banks will almost never finance an off grid property. Also with EVs becoming more common, the ability to connect the EVs battery to your home will become a standard feature. I expect that this feature will also become standard on future EVSE (car chargers) as well. There are some solar array inverters that will interface directly with EVSE. Re-deploying EVs batteries as home backup will also likely become an option in the future for EV batteries that have lost their capacity/usefulness for powering the vehicle.
