Solar, hybrid and tankless water heaters and your choices

With triple digit temperatures last week, we have successfully made the jump right past spring into summer here in the Valley of the Sun.  Here a week of 110 degree weather is considered normal and hot water during the summer is not a choice, it’s the only choice.  Hot water heating can be the second or third biggest energy user in the home, right behind the air conditioner and saving on water heating can knock off up to 20% of your total utility bill.  Using the power of the sun to supply your hot water needs is an efficient method of heating water, but there are more cost effective technologies outlined below that will keep more green in your pocketbook.

A tankless water heater is preferable to solar water heaters for gas-fired tanks.  To prevent cold water sandwiches, tankless water heaters now feature a 20-gallon reserve tank and still heater the water only when needed.  Tankless heaters use a sealed combustion venting type that prevents carbon monoxide from backdrafting into the home or garage.

A hybrid water heater is ideal for Phoenix residents and preferable to solar water heaters if you have an existing electric water heater.  The hybrid water heater uses a heat pump, which sits on top of a traditional electric water heater to heat the water.  The heat pump works just like your refrigerator or AC condenser, but in reverse.  That is it takes the ambient heat out of the surrounding air and uses that to heat the water and expels a small amount of cool air (perfect for a garage application).  Your refrigerator will extract the surrounding cold air and circulate it to provide chilled food while giving off a small amount of heat on the bottom of the unit.  Hybrid water heaters are more than 50% efficient compared to solar water heaters for half the cost.

Solar water heaters may be good for a large family who like to take long showers (most of the energy used to heater water goes to showers).  An 80 gallon tank or two 50 gallon tanks will be installed with solar water heaters, so there will never be a shortage of hot water but can be overkill for most homes.

Some homeowners are even switching from gas water heaters to electric because they are putting solar panels to generate their own electricity.  The thought is that a big enough solar array will cover the energy needed to heat the water.  Solar hot water proponents will argue that homeowners should have both – a solar water heater and a smaller solar electric system because the efficiency of the solar water heaters (1.2 efficiency factor) is greater than the efficiency of a conventional electric (0.89 efficiency factor) or gas tank.  I definitely agree that efficiency steps should be done to stretch that solar electricity dollar, but the cost of a solar water heater makes other water heating options such as a tankless water heater or hybrid water heater a smarter choice (which are all more efficient than using solar electricity).



Bottom line if you are considering solar hot water:

-  Homeowners with gas water heaters and families with children should go with a tankless water heater with a 20 gallon reserve

- Homeowners with electric water heaters should go with a hybrid water heater

- Homeowners should consider solar hot water if they are planning on living in the same house for more than 13 years

How much will solar save?

The Valley of the Sun doesn’t get any better for solar energy production if you are thinking about installing solar panels on your home.  In fact, southern Arizona is the best location for solar in the nation.  APS, SRP and TEP still provide rebates for solar electricity and producing your own energy to spin your meter backwards is an attractive idea to many homeowners and businesses. But how many solar panels do you need to do so? 

Part of the equation is limited to the amount of panels you can fit on your roof, house orientation and external shading and aesthetics.  A good southern exposure is ideal for solar power, however solar panels can be west-facing or on a west-facing slope and angled towards the south.  Some homeowners want to completely zero out their energy bills for the whole year.  Other homeowners go with smaller systems to zero out just their winter energy bills and a lower summer bill.  To calculate the size of photovoltaic’s you will need to accomplish either goal you are going to need your electricity bills for the past 12 months. 

Once you have that, add all the kWh you used each month for the entire year and divide that by 1.7.  The number you get will be the total system size needed to take your annual usage down to zero (if you divide that number by 1,000, you get kW).  So let’s say after I added all the kWh’s used for the year and came up with 23,480 kWh/year (a large home).  Take 23,480 / 1.7 = 13,812 watts.  So I would need 13.8 kW’s of solar panels to completely zero out my energy bills.  Now I can go with half of that number (7 kW system) to reduce my bills by approximately half also. 

The 1.7 factor is an estimate for only a particular type and efficiency of panel, but it will give you a good idea for starters.  If you are a visual person, feel free to contact me and I can send you a spreadsheet where you can enter in your monthly kWh usage, and a nice graph will visually show you what you are spending now on energy bills, and what they would like with a 5 or 10 kW solar electricity system.

For more information visit http://www.dsireusa.org/ to find current APS/SRP or TEP rebates and federal tax incentives for going solar.  Visit APS’s website here, SRP’s website here and TEP’s website here for more tips and information.  Michael Blue Jay also has a great website and solar calculator here.  You can schedule a free site assessment on your home with Green ID to discuss possible options for solar.  For certain homes, coupling solar with efficiency upgrades will stretch your dollar spent 30-40% compared to solar alone.

What are the most common efficiency recommendations for your climate?

I started a new Facebook dicsussion on the most common recommendations for homeowners in southern Arizona. Check it out here and I look forward to learning about common climate-specific recommendations.

Solar leasing has become popular, how about leasing an electric car battery?

The average costs for electricity from APS or SRP is around $0.12 per kWh.  Imagine paying $450 per kWh for electricity.  That’s what most of today’s electric vehicle (EV) owners are paying for a battery to power their cars.  To put this into perspective, the Chevy Volt will cost owners 2 cents per mile to drive compared to the 12 cents per mile on gasoline at a price of $3.60 a gallon.  Or a trip from Phoenix to Tucson would run a measly $1.98 on electricity or almost 6 times that at $11.88 on gas.

 Shocking as the $450 per kWh may be, a decrease to $300 per kWh is considered the tipping point to mass market uptake.  An article published by webtech company, GigaOm, sites that leasing the battery is one solution to bring down the battery costs.  If you have thought about installing solar panels for your home, you’ve probably heard about solar leasing programs or PPA’s for larger solar applications, some groups are applying this concept to the electric car market.  It will be interesting to watch if and how automakers and startup companies adopt the electric vehicle lease; and also how the EV infrastructure is built-up to meet demand.

The cost-effectiveness of switching from an electric to gas water heater

Many homeowners have an old furnace system or gas water heater and want to know if it is cost-effective to switch to an electric heat pump or conventional or hybrid water heater.  By comparing the efficiencies, initial cost and lifetime of the unit you can make an informed decision as to which one is right for you.

Estimated annual energy usage will vary depending on lifestyle but this table gives a good starting point.  Take a look at the annual cost table to get an idea payback and cost-effectiveness for your switch.

Don’t forget the “kicker” factors that also must be considered – such as if you already have gas appliances.  If so, you are already paying around $30 just for having a gas line so you will not be “penalized” for adding a new line (plus $1,000 to have a new gas line tied to your home from Southwest Gas).  This would be a factor if a homeowner had all electric appliances and wanted to switch to a gas tankless water heater.

Save energy while you cook – energy saving tips in the kitchen

Kitchen appliances can account for up to 15% of your home energy usage and how you choose to cook will impact your energy bill.  By following some energy savings tips, you can reduce your bills and here's how.

There is more than one way to skin a cat:

If you took an inventory of all the appliances you use to cook with the list might look something like this: oven, stovetop, slow cooker or crockpot, microwave and toaster oven.

As you can already guess, each of these appliances uses a different amount of energy but what is not so obvious is how much energy each one uses.  When you can choose between making a baked potato in the oven or in the microwave, which one uses less energy?  How about cooking a soup or stew over the stovetop, or using the slowcooker?  Meatloaf in the oven or toaster oven?   Just like if you lived in a smaller house, it would take less time to cool the inside of the home with the same sized AC unit than if you lived in a larger house; it takes less energy to heat a smaller space than a larger one.  So what would use less energy if you could put that meatloaf in a toaster oven compared to the conventional oven?  How much less?  You would be cutting your energy use by more than half! (and reducing the temperature in the kitchen as well).

Of course, each appliance is “specialized” to cook certain foods but when you can choose, I encourage you to do so.  Below is a table showing the energy costs of various cooking methods.

Other energy saving tips in the kitchen include:

-          When using the electric stovetops it is important to match the pan size to the element size, otherwise you will be wasting almost half the heat produced from the element.-          The ideal pan also has a concave bottom to maximize the conduction in the pan.
-          A pressure cooker will also cook stovetop items faster and with less energy because the built-up pressure drops the boiling point of water thus cooking the food faster.
-          Cleaning your appliances increases their efficiency.
-          Avoid peeking into the oven while baking.
-          Double portions when using the oven to save energy on cooking.
-          Remove foil on the bottom of ovens to improve air circulation.

Update on Tax Incentives for Energy Efficiency

The 2011 tax incentive is greatly reduced compared to last year, however there are several efforts to extend residential energy efficiency credits for measures such as water heaters, heat pumps and windows that are no longer available. Green Parent Chicago gives some great resources to keep up to date on the tax credits and I've posted a 2011 federal tax credit summary for energy efficiency improvements here as well.