Off-Grid Lessons Learned

On April 2nd I wrote about our plans to install an off-grid solar system with Aquion batteries on our new bamboo home on the Big Island of Hawaii. It seemed we had little choice. Off-grid solar was less expensive than hooking up to the electrical grid.

 

Our bali-style bamboo house has nine 275 watt photovoltaic solar panels.

Our bali-style bamboo house has nine 275 watt photovoltaic solar panels.

Seven months later, we live in the home and monitor our 2,475 watt off-grid system on a daily basis. Nine 275-watt panels are mounted on the south-facing roof and an Outback Inverter system and six Aquion 48-volt batteries manage the electrical storage and conversion to the usual AC (alternating) current of our 1,180 square foot home.

 

We rented another home for the 9 months it took to get through this building project that was also off-grid solar. It had lead-acid batteries and I had a taste of monthly checks of the batteries and addition of distilled water. I could hear the boiling liquid in the batteries on sunny mornings. I used a hygrometer to check the condition of the batteries with coaching from a neighbor. I knew to be careful with any acid spillover and scrubbed away corrosion with a bicarbonate of soda bath. When our electricity suddenly disappeared one day, I asked our solar contractor at the new house to look at the system. He found a loose connection where acid had totally eaten away the bolt connection. He quickly fixed it and it all worked again. It was a lesson in the importance of careful maintenance with lead-acid batteries.

 

Six Aquion S20+ saltwater batteries sit behind the house in their own shelter, storing electricity each day.

Six Aquion S20+ saltwater batteries sit behind the house in their own shelter, storing electricity each day.

I generally like new technologies because they often demystify existing technology. I am a new adopter with home computer devices but I am not usually a new adopter with mechanical or electrical systems. Off-grid solar systems seemed to teeter on that uncomfortable edge of being a little too technical for me. But we took the plunge into off-grid solar for good reasons. We like getting away from fossil fuels. We love supporting new technologies that make sense. We love the idea of not having an energy bill monthly. It was simply cheaper up front with the great tax credits from the state and federal government. So, HOW DID IT GO?

 

It’s been great, actually.

 

  • We have no electrical bill at all. On-grid charges in Hawaii are 48 cents a kilowatt hour, about 4 times the rate in most of the U.S.
  • Our viewscape of the ocean is uninterrupted by power poles. On-grid we would have had to install about $20,000 in ugly power poles, that due to the easements, would have obscured our view. Here you have to drill into solid rock to put in transmission poles and that doesn’t come cheap or easy.
  • An Outback Invert regulates the system and converts the DC storage to AC current for the home.

    An Outback Invert regulates the system and converts the DC storage to AC current for the home.

    The entire system we ended up with cost $24,000, but tax credits give back $11,500. Payback for this system from savings with no electric bill is likely about four or five years.

  • We worried that a 2.475 kilowatt system might not be enough to support our needs so living with it has been a learning experience. We usually draw down the batteries about 15% each night with daily use of a refrigerator, microwave, low-speed overhead fans, lighting and electronics. We also run the washing machine once or twice a week. If we get four hours of good sunlight on any given day, it brings the batteries back up to 100% by noon.
  • It would take seven days of no sun at all to draw down the system to 0 and that just doesn’t happen here. The system has a generator backup system that we likely will never need. With saltwater batteries it is okay to draw batteries down below 50% (a bad idea with lead-acid batteries).
  • We installed propane for cooking and a dryer because stoves and dryers require 220-volt power. Our system only produces 110 volts, a choice we made to save some installation dollars.
  • We went with a Solahart 80-gallon unit for hot water at an extra cost of $7,000 with a 30% federal tax credit (so $5,000 as an after-tax expense.) A heat pump would have met the state requirement for being solar powered because it would get its energy from our photovoltaic cells and would have cost one-fourth as much. We didn’t fully understand this until we were committed on the Solahart system. It works well and we are happy with it, but the heat pump option would have been easier and less expensive and if we had to do it over, we would probably go that route.
  • The control panel shows us the level of charge at any time we wish to check.

    The control panel shows us the level of charge at any time we wish to check.

    We simply have no maintenance requirements with the saltwater batteries. Checking the battery storage level daily is reassuring, but is not really necessary for the system performs as promised. RES, a family-owned business in Honokaa, has been our contractor and their installation work went very well and it all works as expected.

 

Certainly, there will be lessons to be learned over time. Aquion batteries are sealed, require no maintenance and should last 20 to 30 years, but time will tell. This is technology available only in the last few years so we

A Solahart 80 gallon collector heats and stores water for our home.

A Solahart 80 gallon collector heats and stores water for our home.

took the risk of seeing how long these batteries will last, having only the manufacturer’s projections.

 

The tax credit incentives provided by the federal government and most state governments are “window in time” opportunities. Eventually the window will close and those incentives will disappear, but they are making affordable solar energy systems a great bargain in most situations. If you haven’t looked into the costs and potential return on investment, now is the time to take a look. The sun will always be shining for you but you have to have the right system to take advantage of it for your home or business.

 

– Tim Merriman

 

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