Using fewer fossil fuels is a goal that is increasingly popular. And it certainly helps if it is a financial benefit as well.

We have mostly weaned ourselves off of oil for transportation – We have an EV that is fueled largely from hydroelectric and other renewable sources. Our electric cargo bike has reduced car mileage even further.

Next up is optimization of our home. We now have some shiny new solar panels on our roof.

Going Solar

In December 2021 our new solar system was connected to the grid. It consists of twenty 380 Watt panels (7.6 kW), an inverter, and a 2nd power meter to track excess production pushed into the grid.

Energy production isn’t so great around the equinox but our March bill will be negative for the first time. (Total usage of 688 kWH with production of 863 kWH, so excess production of 165 kWH.) We shall see if it stays negative as air conditioner usage begins in May or thereabouts.

There is an app that we can use to track energy production throughout the day. It is kinda cool. This graph shows a day where the panels produced 30 kWH – you can even see where a cloud got in the way of the sun in the early afternoon.

Net Metering

Our electric company uses something called net metering – they pay us for any kWH we push onto the grid. Currently they pay us the retail rate.

This varies by season and time of day. Now that daylight saving time has sprung ahead our panels will have an extra hour of production during Peak times.

May – August we will get a full 3 hours of production during Peak times. For the rest of March and all of April/September we will get ~2.5 hours of Peak sunshine (sun sets at 7:30-ish.)

We also get a 1.5c/kWH credit for 12-6 am for EV charging. Weekends and Holidays are 100% Off-peak.

Cost

I got quotes from 3 different solar companies / general contractors. The most expensive by far was those guys at Costco.

I paid $21,000 inclusive for the permits, install, materials, and addition of a 240V 60A line and circuit breaker for EV charging. The IRS pays 26% of this ($5,460) in the form of a tax credit on our 2021 tax return (Form 5695.) This comes with a 25 year warranty on materials AND labor.

There are options to lease or finance the panels but I just paid cash (or paid for it out of our mortgage which would add a 2.75% interest expense.)

According to the solar company, we should generate ~10,600 kWH/year. This would put us at a break even point of about 4.8 years (~$2.8k/year savings) after which we get another 20 years of free-ish electricity (25 year panel life, estimated.) The nice thing with net metering is how much energy we use is irrelevant for the cost analysis – any excess production gets a dollar for dollar credit. We are actually ahead of the break-even projections (165 kWH excess production in March vs projected 111 kWH.)

It’s important to take these solar company projections with a grain of salt. They didn’t have old energy bills to work with so everything is an educated guesstimate. Our actual electric usage has been above the pre-solar consumption estimates, for example. I also did my own projections before committing and think our breakeven point will be closer to 6 years, but it really does depend on how much summer peak kWH we generate (those 35…. still, a 6 year break even is a nice ~17% return.)

What about storage?

Adding storage (a big battery) to the solution was going to add $10,000+ and has questionable value for non-emergency use.

A Tesla Powerwall 2 holds 13.5 kWH. If we were to charge if from 0 to 100% at our discounted EV rate at midnight and then discharge is 100% during summer peak hours ($0.3215/kWH benefit) it would provide a daily benefit of $2.76. If it was always summer the breakeven point would be 3,627 days or ~10 years, which is not so bad. 10% ROI, etc…  But it isn’t summer rates all the time so the break even date comes to 20 years.

At $5k or less installed it would be interesting. That could come as a result of cost efficiency or subsidies (or both.) Until then… no.

Summary

We put some solar panels on our roof. After tax benefits we should break even on the cost of install in 5-6 years, after which we will get another 20 years of low-carbon energy production.

The benefits and ROI seem worth it.

Do you have solar?