Tracking 2026 Solar Production, Electricity Use, Battery SOC, and Generator Use

I tried to improve and automate our 2026 tracking of solar production, energy use, minimum battery state of charge, and whether we needed to use a generator on any given day, at our off-grid property in midcoast Maine. If you want to see similar information and data for 2025, you can find it here.

All data resets about three minutes before midnight each night (you need a slight offset to make sure the data is appended to the Google Sheet before it resets for the night). The biggest improvement for 2026 is string level data (in addition to total production) and I’ve now added tracking for both the house and the studio (each has its own, autonomous solar production and batteries). I plan to add similar tracking for my small office system in the next week or two. My hope is that by providing data for buildings/systems of different sizes, it might help someone trying to design and build their own system.

The house (barnpartment) system is a 20KW system comprised of six strings feeding 70 kWH of batteries. The 4 KW gambrel roof is 67 degrees, while all other strings are 3.2KW. The verticals are of course 90 degrees, and the four ground mounts are all bifacial panels mounted at a 45 degree tilt. All face within a few degrees of 180 (due south) as best I could align them by sight and using a phone app.

The studio, which has its own, autonomous energy system, also facese due south with a 4 KW string on the 45-degree roof and a 2.8 KW string of verticals on the side of the building, but with the limitation of a 5,760W maximum output for the charge controller. This system has 28.8 kWh of batteries.

Here’s the link to the house (the “barnpartment”, as I call it) 2026 data:

Here’s the link to the 2026 studio data.

We had hoped to use heat pumps for all our heating and cooling, but being skeptical, we built both buildings with radiant slabs as well (not something you can do after you pour that concrete!). I’m glad we did that, despite the extra expense. We do use heat pumps in both buildings for cooling, and for heating in shoulder seasons. But for heating the garage and entry foyer of the house, and for all of the studio, we use a propane-fueled radiant (hydronic) slab during winter because we found that an air-air heat pump requires too much energy on cloudy days (remember, we’re totally off grid). We hope to eventually use an air-water heat pump for those radiant systems instead of propane, but air-water heat pumps that will work well during our cold winters are still too expensive in the US to justify that capital cost. We’re hoping that changes in the next few years, but until then, we use propane for those heating systems, EXCEPT…

…when we can use free energy from the sun. The solar energy system in each building is capable of using excess solar energy (which occurs on most sunny days) to provide that heat, by powering a “dump load” when we're getting much sun and the batteries are nearing full charge. A dump load is simply a load that is powered only when a system is making more energy than is needed to power all the other loads and keep the batteries charged up (i.e., excess energy). In each building these are electric heaters that power that building's hydronic heating system buffer tank. The house dump load is about 7,100 W, while the studio's is about 3050W (I disconnected one of that tanks's heaters because of the smaller PV array). I automated whether these come on, and when they turn off, using home automation systems (another hobby). They work really well and during periods of sun in the winter we are sometimes able to go several days without needed to use the propane boilers, even when it never gets to 20 degrees Fahrenheit and when nighttime temps are below 0F. Hat tip to my friend Joe F for suggesting this approach.

In the data, “Net Loads” are simply the total daily energy use for the building, less the energy used by the buffer tank heater(s). “Net Energy” is total daily PV production less Net Loads. “Net Battery” is the amount of energy that went into the batteries less the amount of energy we pulled out of them. If you see an “X” in the generator column for a date, we needed to run the generator that day to make sure we had enough energy. If there’s no “X”, there was no use of a generator (we didn’t use one at all in 2025 - fingers crossed for ‘26!).

I hope this information is helpful to people who might be thinking of also going off grid. It’s certainly possible, and not nearly as hard as you might think.