A Family Adventure


Tyson, Emilie & Isaac

First Year Net Zero

Emilie Phillips

Our PV solar panels have been installed for a year. We generated 10.75MWh of electricity. Our utility meter says we sold 7,373kWh of that back to the grid. And we used 6,880kWh from the grid. So net, we used 490kWh less than we produced! Our load is dreadfully mismatched with production. We are shipping 3/4 of our production to the grid and then taking it right back. Some of the mismatch is daily — we are at work when the sun is shining. Some of it is seasonal. The most likely culprit for the seasonal imbalance is the hot tub.

Net meter readings

PV production

To verify how much energy we used, I had to figure out the Itron utility meter display. It’s anything but intuitive. The best resource I found was the Eversource FAQ. But while hunting around the internet, I found the generic Itron installation manual. It says the Itron meters use hall sensors to detect energy usage. According to this report, meters with hall sensors can systematically under-report energy usage. Obviously, whatever the meter says is how we are billed, so we will be billed as net zero. But I wanted to know “are we really net zero?” I did a quick comparison of a couple months of utility bills to data from my Sense monitor. They came out similar. So it looks like my smart reader is reasonably accurate.

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  • As you already know, energy conscious living is more than producing your own power, it is also using less of it.what kind of lifestyle changes can you make to reduce energy consumption AND, what changes are you willing to make?

    • We put a lot of effort into building a house that takes little energy to heat, but we haven’t been as rigorous with our electrical usage. My Sense energy monitor tells me that always on electronics and ERV are my biggest consumer. Next biggest is the hot tub. Those two account for almost half the yearly consumption. Everything after that is small.

      I’ve had a heck of a time tracking down what is always on. As for the hot tub, that gets to your comments about lifestyle changes.

      • I am having a small struggle with my always on electronics right now. I upgraded to a 24 volt system and decided to go with an AIMS 3000 watt inverter. When only always on electronics are plugged in, the inverter idles near 120 watts. Previous inverter idled at 50-60 watts. I’ll be looking to run my always on electronics on DC power so the inverter can go into sleep mode. Those things are only my wifi router, satellite internet modem, a couple IOT devices, and maybe a fan sometimes. That should bring my total idle energy consumption to under 50 watts.

        How about a wood fired hot tub? https://www.popularmechanics.com/home/outdoor-projects/g13938995/build-a-wood-fired-hot-tub/

        • 50W is good for a modern house. And yet, 100 years ago, idle electricity usage was 0.

          Switching the hot tub to wood doesn’t reduce it’s total energy usage, just switches the type of energy. A sauna would use a lot less energy because it can get cold when not in use. But you can’t stargaze from a sauna. The equivalent for a hot tub would be one that drained back to a storage tank inside.

          One of my goals is to reduce the number of servers. Right now they take 76W at idle. If I could reduce the number of servers and switch to flash drives instead of spinning drives that should get better.

          I have all the media center on power strips, so I can turn that off.

          I am pretty sure our always on increased when we replaced our light switches with z-wave controlled switches.

          Various HVAC components add up to 60W idle.