Information on Estimated Monthly Electric Costs in Hawaii

I received the information in this chart from one of the contractors I approached for an estimate on a solar hot water heating system.  The chart he had didn't attribute a source, but I believe he told me he got it from HELCO.  I searched the web for a similar chart, but I couldn't find one.  At any rate, I think it is a helpful starting point when you are analyzing your electrical use and trying to make decisions about how best to conserve energy or investigate alternative energy sources.

Go Solar! Solar Hot Water System

In my conversation with my engineer friend Steve, I learned that solar hot water systems are different from photovoltaic systems and that they are installed separately.  Solar hot water systems use solar energy to directly heat water.  Photovoltaic systems use solar energy to produce electricity.  Solar hot water systems are more like plumbing projects and photovoltaic systems are electrical projects.  If you think about it that way, it makes sense that installations of hot water systems  and photovoltaic systems are generally handled by different contractors, at least where I live.

I started compiling a list of possible contractors for each of the two projects by talking to friends who had solar water and/or PV systems to get their recommendations, and by doing a phone book and web search.  Once I had honed my list to four likely contractors for each project, I started making phone calls to request estimates.

The solar hot water installers were the quickest to respond.  In fact, most of them were willing to give a ballpark cost estimate over the phone, even prior to a home visit.  The basic question they asked in order to provide an estimate was "how many people are living in the home"?  I am assuming that they feel this is a pretty reliable indicator because the number of occupants correlates pretty accurately with the number of showers, loads of laundry, dishes washed and other household hot water requirements.  In fact, the most significant variable that seemed to be up for discussion was whether the water tank should be 80 gallons or 120 gallons. Without exception, the contractors recommended an 80 gallon tank for our 2-person household.

All of the general information I found available on the web stated that solar hot water made economic sense for pretty much everyone in Hawaii.  Right now, this seems especially true because there are tax credits available from the Federal and Hawaii Departments of Revenue, AND an additional $750 instant rebate through the Hawaii Energy Efficiency Program (HEEP).  HEEP has extensive installation requirements, but our solar water contractor was familiar with all of them and made the receipt of the instant credit absolutely seemless to us.  Here is a great link providing information on the $750 credit, the cost of an average solar hot water system in the state of Hawaii, and a pie chart on residential hot water use in Hawaii.  http://www.hawaiienergy.com/16/water-heating#solar-water-heating

I concluded that the decision about whether to install a solar hot water system or not was a no-brainer.  Why is that?  The systems are tried and true in Hawaii.  They are good for the planet.  Financially, they make great sense.  Here is the calculation showing the final net cost for our solar hot water system:

Based on the net cost above, I calculated an ultra-conservative estimate of the payback period for my solar hot water system.  Assuming that my current average daily hot water heating requirement is 6.8 kilowatt hours per day (30% of 22.8 kilowatt hours), that the solar hot water system will reduce that requirement by 80% (most sites say 90%!), and an average current cost per kilowatt hour of 40 cents (the cost on my last bill was 44 cents!), the pay-back period on my system will be about 26 months.  Using less, but still conservative, estimates for some of these values, I believe that it could take as few as 18 or 20 months for full pay-back.  One other factor that contributes to the financial wisdom of converting to solar water heating now is that we were very close to end of life on our existing water heater and would likely have had to replace it in the not too distant future.  So, the cost of the solar storage tank itself could feasibly be backed out as a "wash", making the pay back period even shorter.

Our contractor came highly recommended by former customers and fulfilled their promise of installing the system in a single day.  We have less than two weeks experience with the system, but we are very happy so far.  We have hit a rainy spell, so our savings in this early period may be lower than average.  But we have been able to test the full range of the system and are assured that the automatic timers that check the water temperature at proscribed times and allow the water in the tank to be heated conventionally if necessary works perfectly.

For people interested in the technical specifications of our system, here is the information on the system components:

1. 2 - 3' X 8' EP-24 solar collectors (SunEarth manufacturers)
2. 1 - 80 gallon solar storage tank with electric assist (Ruud manufacturers)
3. 1 - Auto-controller, differential thermostatic (Independent Energy-Goldline)
4. 1 - Solar re-circulation pump (Grundfos SU-15)

 

Solar Radiation Map for Hawaii Island

In my November 7, 2011 blog post on estimating PV system size, I published a link to the Solar Radiation Maps for the major Hawaiian islands and an Energy Conversion Table.  I've just learned that the links from that page to the specific information are currently broken.  The state Energy Office is creating a new website and will eventually include the information in their new web site.  I'll publish the new link when it is available.  In the meantime, just as an example, here are the map for Hawaii island and the conversion chart that were used for obtaining the information on average peak hours of sun used in the equation provided in that post.

Go Solar! Estimating PV system size.

I live in Hawaii and have been dreaming of "going solar" for a few years.  I'll admit that my main incentive for doing so was the allure of saving money.  Electricity in Hawaii is very expensive, in large part because the state depends on imported oil for about 76 percent of its electricity needs.  There have been months where I have paid 45 cents per kilowatt-hour for my electricity.  (In 2010, the national average was 11.5 cents per kilowatt-hour.)  Reading how high my electricity bill is probably makes you wonder why I have waited so long to move to alternative sources. Initially, I was waiting for the cost of some of those alternatives to come down.  Then in the last couple of years, I just couldn't find the time or energy to do the research required to make a sensible purchase.  In September 2011, I felt it was high time I got this project in gear.

My engineer friend, Steve, one of the most able and trustworthy people I know, is passionate about alternative energy and I contacted him to see if he had time to install a photovoltaic system for me before the end of the year.  Unfortunately for me, he did not have time to do the work, but he generously offered to come over to review my situation and give me some pointers.  He spent a couple of hours at my home and left me with a valuable basic understanding of PV systems.  He also did some back of the envelop calculations that gave me a ballpark idea of the size of the system I should contemplate building.  Thank you so much, Steve!

Ok.  What kind of information did we use to estimate system size?

1. How much energy do you generally use?  Consult your past electric bills to calculate this information.  In my case, the average use for 2 adults in our household over a 12 month period was 22.8 kilowatt-hours per day.
2. How much sun does the area usually get?  The average number of peak sun hours per day in my area is about 4.8.  The Hawaii State Geographic Information System (GIS) has links to Solar Radiation Maps for each of the major Hawaiian Islands and an energy unit conversion table on their web site.  Here's the link: http://hawaii.gov/dbedt/gis/miscmaps.htm
3. Where will you put your solar panels and how is the site oriented to the sun's path?  Our roof is very high and unshaded by trees, buildings or other obstructions in the sun's path.  It is also oriented with its roof-line on basically a southeast to northwest axis.  This is a terrific piece of luck.  Steve had a gizmo that looked at the sun's path in relationship to my roof.  A solar contractor has access to similar instruments.
4. What do you usually use electricity for?  The idea here is to take stock of your energy use and decide on an appliance-by-appliance basis if you could benefit by changing your approach.  In Hawaii, heating water accounts for about 30% of the typical electric bill.  Clearly, examining our approach to hot water heating should be first on our list.  A little on-line research told us that a solar hot water system was likely to reduce our hot water heating bill by about 90%, so we decided to install a solar hot water heater as our first priority.  (See a separate post on the solar hot water system.)  Going down the list of our other large appliances, we determined that our gas stove was a good thing, our old refrigerator should be replaced with a more efficient model when it is financially practical to do so, and that we would stick with our electric dryer rather than buying a propane dryer, at least for the time being.  Our dryer is in good condition, so I'd hate to replace it now.  Also, we paid $5.60 per gallon for propane purchased today.  That's pretty expensive and likely to go up as time goes on.  So, for the purposes of estimating the size of a PV system, we decided to use our current average less the probable effect of a solar water system.
5. Here's the equation Steve shared with me: Kilowatt Array Size = Kilowatts Required  /  (Efficiency of the System  X  Ave Peak Hours of Sun).  The amount of Energy we want to generate is about 16.6 kilowatt hours per day.  This is our 22.8 average use, less 90% of 30% of that same number in order to allow for the likely contribution of the solar water system.  Steve estimated the efficiency of a PV system at 70%.  Our Average Peak Hours of Sun is 4.8 hours/day.  Kilowatt Array Size = 16.6/(0.7 X 4.8) = 4.94.  So, we determined the likely size of our system should be about 5 Kilowatts.

These were Steve's back of the envelop calculations.  My next step would be to consult with some solar contractors to get their opinions on the system we should build.  To be continued in another post.

Make a video with your dog!

We have three dogs; Ida, Kiko and Reggie.  It is not a dog family that was planned.  Each of the three dogs found us when they desperately needed a home.  Reggie, the latest addition presented himself in March.  He was still a puppy and was in very poor shape, starving and suffering from a condition generally referred to as genetic mange.  As he laid just outside our fence, Ida and Kiko discovered him and stayed near him until human help arrived.  He is now fully recovered and well on his way to becoming a very well-behaved dog.  Between then and now, there were medical treatments, a lot of TLC and a few episodes of puppy aggravation.  For example, he went through a short stage where he was devoted to searching and destroying telephone books.  We're still not sure how he found the phone books, but we are very clear on how much he loved to shred them when he was home without human supervision.  Here is a video where I am having a serious chat with Reggie about his phone book shredding behavior.

Life is an adventure!

I'm not working.  I thought I'd be lost if I ever found myself in this circumstance, but I'm not!  Instead I have re-discovered activities that I always enjoyed but never seemed to have time to do, and have encountered new activities and interests that are enjoyable and fulfilling in their own right.  These days, I am happily engaged in the present.  But every now and then when I do look back, I ask myself why I didn't do more of what I'm doing now when I was gainfully employed?  So, this blog is about leisure time, whether you have a little or a lot of it.  Some of the entries will be about practical things, some may be useless but interesting, and others are likely to be just plain silly.  I'm looking forward to watching it naturally unfold because, after all, life is truly an adventure!