A few years ago I started writing regularly about electric cars and the batteries that power them—technologies that are helping humanity transition away from reliance on fossil fuels. And as bad news continued to pile up about the harms caused by climate change, I started to think harder about my own carbon footprint.

So last year, my wife and I got solar panels for our roof. Then we replaced our air conditioner, getting a model with a heat pump capability. Shortly after that, our boiler sprang a leak and we got a new high-efficiency boiler. Then we purchased a battery electric car.

We haven’t yet achieved a carbon-free lifestyle. The new boiler burns natural gas and we’re keeping our old gasoline-powered car. We also have an oven and fireplace that run on natural gas. Still, our carbon emissions in 2021 will be far lower than they were in 2019. And we’re on a path to radically reduce our carbon emissions over the next decade.

Government policies were a big help here. The federal government offers generous incentives for the purchase of solar panels and electric vehicles. The District of Columbia, where we live, offers additional incentives for both. Not only did these directly reduce our out-of-pocket costs, they have also helped manufacturers achieve economies of scale that made these technologies affordable in the first place.

So I thought walking through the experience might inform—and perhaps inspire—others who might be considering taking a similar leap.

Rooftop solar

My green energy odyssey started with solar panels. My wife and I live in a Washington DC row house with a gently-sloping, south-facing roof. With no tall trees behind the house, it’s ideal for generating power all day long.

In the spring of 2019, I got quotes from two solar companies. One company wanted $35,538 for a 8.5 kW system with 26 panels. The other firm quoted us $33,372 for a 8.64 kW system with 24 panels. In either case, we’d get a 30 percent federal tax credit worth more than $10,000, bringing the net cost below $25,000.

We decided to go with the more expensive vendor. The cheaper bidder wanted to anchor the solar panels directly to the roof, while the more expensive proposal would suspend the panels from beams mounted on the parapet walls on either side. The first firm assured me that they could seal the roof up good as new, but the idea of cutting into the roof made me nervous.

Later, the winning contractor told us that our roof was nearing the end of its life and would cost more to replace after solar panels had been installed. So we decided to have them replace our roof. Our chimney was also in bad shape, so we had a different company rebuild that. This added $17,482 to the cost of the project. We financed all of this—and the HVAC upgrades I’ll discuss shortly—with a home equity loan.

The roof was installed in early August. The solar panels arrived in October. Then there was a month’s wait for Pepco to hook up the system to the electric grid. Our system was finally active in November 2019.

Solar panels only generate power in the daytime. So if we wanted to build a self-contained system, we would have needed to buy batteries to store excess power in the day and for use at night. But luckily for us, DC law requires our electric utility, Pepco, to do what’s known as net metering. When we have excess power, Pepco credits us at retail rates, effectively providing us with free energy storage.

Our solar panels will pay for themselves in five years

In 13 months of operation, our system has generated more than 11 MWh of power, which our solar system’s website estimates saved us $1,250. Our electric bills reflect that. In the year before the solar panels were installed, our electric bills totaled $1,254. Over the following year, we paid only $72.

Still it would have taken more than 20 years for the solar panels to pay for themselves based only on these electricity savings. Luckily, free electricity wasn’t the primary benefit for us.

Under DC law, Pepco must acquire a rising share of its electricity from renewable sources. Pepco can either generate renewable power itself or buy solar renewable energy credits (SRECs) from third parties like us.

Thanks to DC’s stringent green energy requirements, SRECs in the district sell for more than $400. Each SREC represents 1 MWh of electric power, so our solar panels generate about 10 SRECs per year. Hence we can expect as much as $4,000 per year in SREC income. So far we’ve gotten three quarterly payments totaling $3,647.

When you combine SREC revenues with our electricity savings, the solar panels are likely to pay for themselves in about five years.

Americans outside of DC probably won’t get such a good deal. Many states don’t have an SREC program, and the ones that do have lower SREC prices.

When we installed our solar panels in 2019, they were eligible for a 30 percent federal credit. That figure dropped to 26 percent for 2020. It was scheduled to drop to 22 percent in 2021 and to zero in 2022. However, Congress just passed legislation to extend these deadlines by two years. So the 26 percent credit will now be available through the end of 2022. Then it’ll fall to 22 percent in 2023 and to zero after that.

On the other hand, the cost of solar panels keeps dropping. And some parts of the country get more sun than Washington DC. So if you live in one of America’s sunnier states, you may find that solar panels are a good investment even with little or no state help. And regardless, it’s good for the environment.

HVAC overhaul

When we decided to replace our air conditioner in early 2020, we weren’t thinking about reducing our carbon footprint. The condenser for our old air conditioning system was noisy and took up space in our tiny backyard. As we made plans to put solar panels on our roof, we wondered if we could put the condenser on the roof as well.

Our initial plan to do both at the same time didn’t work out. But a few months after the solar panels were installed, I hired a company to install a new system on the roof, since the old one was nearing the end of its life.

We decided to pay an extra $1,000 or so for a version that doubled as a heat pump that could heat our house as well as cooling it. In total, the air conditioning system—including heat pump capability and crane rental—cost $12,666. Buying the heat pump likely makes us eligible for a $300 federal tax credit as well as a rebate from the District of Columbia.

Weeks after the new air conditioner was installed, the oil-fired boiler that feeds our radiators sprang a leak, creating a puddle of water on the basement floor. I’d been wanting to get rid of that old boiler—and the enormous oil tank in our basement—for years. The leak accelerated our timetable. Rather than trying to salvage our aging boiler, we decided to replace it. It was July, so we had plenty of time to get a new one.

After researching the options, we decided to get a high-efficiency condensing model. We got a “combi” unit that doubles as a tankless water heater. It hangs on the wall and takes up dramatically less space than our separate boiler and water heater had before. It cost $10,500. I got an $825 rebate from the District of Columbia and may be eligible for a $150 federal tax credit.

Conventional boilers waste heat by sending a lot of steam up the chimney. A condensing boiler, in contrast, cools down exhaust gases to turn most of that steam back into water, extracting a few extra percentage points of heat in the process. These cooler, moister exhaust gases can’t go up a conventional chimney. Instead, condensing boilers use a plastic exhaust pipe that sticks out of the side of the house—angled slightly downward so the condensing water runs outside.

https://arstechnica.com/?p=1729668