2025 Solar Production, Electricity Use, Battery SOC, and Generator Use
Here’s a Google Sheet that shows our daily solar production, energy use, minimum battery state of charge (SOC), and whether we needed to use a generator, for every day in 2025. The link allows you to view the file or to download it if you think it would be useful.
Googe Sheet: 2025 Solar Production-Energy Use-SOC-Gen Use
We have more than one building with its own solar energy system now, but the system for the main house is the only one for which I’ve captured data for the full year. I plan to capture and share info for the other buildings in 2026.
2025 was our first full year living off grid (no connection to the electric utility). We started the year reasonably confident that all would be well but one never knows what to expect until you’ve lived through a full winter with no access to the power company. So, what did 2025 bring? I’m happy to report the following:
We did not need to use a generator even once during 2025. Not a single minute. We had planned for up to six days of generator use when we designed the system, and we’d start the generators (we always have a backup to the backup because “two is one, one is none”) once per month to make sure they were working properly. But somewhat to our surprise, we didn’t need a single watt that wasn’t produced by our solar panels.
December was our highest month of energy use, but that’s skewed a bit by that month’s introduction of a “dump load” that allows us to make productive use of extra power we found we could generate on sunny days (electric heaters in the buffer tank of our radiant heating system. There are other posts on the blog that discuss that project). Without the dump load, January would have been our biggest month for energy needed, at 687 kWH. With the buffer tank “dump load”, we used over 900 kWh in December, but a big portion of that was just excess energy heating the radiant slab, reducing our need for propane.
The same situation holds true for our electricity production. January was our biggest month (other than the dump load) with over 900 kWh produced. Including the dump load, December showed a whopping 1.1 mWh of production (yes, over a megawatt)!
From January - March, our lowest battery SOC was 44%, which really surprised us. But we were still being careful with energy use at that point because we didn’t really know what to expect. We didn’t do anything drastic, but we were just careful not to use too much energy on or before cloudy days. As we got into the latter part of the year and had some experience under our belts, we relaxed considerably. We got down to 25% SOC one day in November, and then on Christmas Day, after a week of frankly not being careful at all with energy use and an unexpectedly cloudy day on Christmas eve, we got down to 15% on Christmas day. That was close! But then we got some sun, and “the streak” of no generator use was preserved.
The 13.6 KW of panels and 70 kWh of batteries I designed for the building ended up being just about perfect for our needs; however, when the federal government announced the end of tax credits for residential solar after 2025 (stupid, stupid, stupid policy change), our accountant told us that if we were going to expand our system in the foreseeable future, we’d be much better off doing it this year. With retirement on the horizon in the next three years and a desire for an EV or two at some point, we decided to accelerate our plans for the panels needed to power an EV, and put in an additional 6.4 KW that went live on Dec 5. That’s when our production went off the charts on sunny days, and we started dumping that extra production into the radiant heat buffer tank. Again, I talk about that in other posts.
With the power from those extra panels now available, we feel even more confident about 2026. There’s always the possibility - even probability - that a generator will be needed every once in a while. But when we lived on-grid in our previous home, we needed a generator for several days, several times each year. Based on our 2025 experience, neither of us have had one moment of regret about going off grid, and we’d advocate it for anyone that has the room to generate and store a sufficient amount of solar power. If you’re building a new home and have the space for panels and batteries, we think it’s a great choice. It’s nice to have no power outages, and no power bill, and frankly we’ve felt more “secure” over the past year from an energy perspective than at any time in our lives.