Many homeowners are interested in reducing their energy costs and environmental impact. Installing a solar hot water system is one way to achieve both of those goals. But is it really cheaper than a traditional gas hot water system? There are a few key factors to consider when comparing solar hot water vs gas hot water.
Upfront Costs
The initial purchase and installation cost of a solar hot water system is higher than that of a gas system. A typical solar hot water system costs $6,000-$10,000 installed. This includes the solar collectors, storage tank, pipes, and other components. A gas hot water heater can be purchased and installed for $1,000-$2,000 on average.
So in terms of upfront costs, gas hot water is clearly cheaper. However, solar hot water can pay for itself over time through energy bill savings.
Operating Costs
While a gas system is cheaper to purchase initially, operating costs over the lifetime of the system tell a different story. Gas hot water systems require gas to heat the water. This ongoing fuel cost can really add up. Electricity may also be required to power controls and fans.
Solar hot water systems rely primarily on free energy from the sun. This means little to no operating costs for fuel. The only electrical use is for pumping water between collectors and storage. Overall, solar hot water can save $200-$550 per year compared to gas hot water when electricity and gas prices are factored in.
System Lifespan
The lifespan of a solar hot water system is typically longer than that of a gas system. Properly installed and maintained solar collectors can last 25-30 years. Gas hot water tanks need replacement every 8-15 years.
This means that over a 25 year period for example, a gas hot water heater would need replacement at least once. The solar hot water system would function effectively for the entire time with minimal maintenance.
Efficiency
Solar hot water systems are remarkably efficient when designed and sized properly. The solar collectors can capture 50-80% of the sun’s energy. After the initial heating, well-insulated tanks retain heat well to provide hot water when needed.
Gas hot water heaters are less efficient, converting only about 75-80% of the supplied gas into useful heat for the water. The tanks also lose some heat over time while waiting to be used.
Incentives and Tax Credits
There are often strong financial incentives available for installing solar hot water such as tax credits and utility rebates. A 30% federal tax credit is currently available for solar hot water installation costs. Local rebates of up to $1,000 may also be available.
Gas hot water systems do not receive these types of incentives. When the long-term tax savings are calculated, solar hot water becomes even more cost effective.
Cost and Savings Comparison
Let’s compare total costs and savings over 20 years for a typical solar hot water system versus a gas hot water heater.
Solar Hot Water System
– Initial purchase and install cost: $8,000
– Minus 30% federal tax credit: -$2,400
– Net cost after tax credit: $5,600
– Annual electricity cost for pumping: $100
– Annual maintenance cost: $50
– Total 20 year energy and maintenance costs: $3,000
– Total 20 year cost: $5,600 (initial investment) + $3,000 (energy and maintenance) = $8,600
Gas Hot Water Heater
– Initial purchase and install cost: $1,500
– No tax credit benefit
– Annual gas cost: $350
– Annual electricity cost: $40
– New heater replacement at year 10: $1,500 installed
– Annual maintenance cost: $50
– Total 20 year energy and maintenance costs: $7,900
– Total 20 year cost: $1,500 (initial investment) + $7,900 (energy and maintenance) = $9,400
In this example, the total 20 year cost of the solar hot water system is about $800 less than the gas hot water heater. And this is using conservative estimates – the savings could be even greater depending on energy prices and usage.
Payback Period
How long does it take for the upfront cost of a solar hot water system to be paid back through energy savings? This is called the payback period, and helps evaluate the return on investment.
For the costs used in the example above, the payback period is about 6-7 years. By avoiding about $350 per year in gas costs, the initial $5,600 net investment (after tax credits) is paid off in 6-7 years. After this payback period, the additional 15+ years of system life provides free hot water!
The exact payback period can vary considerably based on these factors:
– Installation cost
– Available tax credits and incentives
– Local energy prices
– Hot water usage and demand
Under optimal conditions, the payback period can be under 5 years. This makes solar hot water an attractive investment given the system lifespan of 25+ years.
Benefits of Solar Hot Water
Installing solar hot water offers a number of benefits beyond just cost savings:
Lower Environmental Impact
Solar hot water reduces reliance on fossil fuels. This lowers carbon emissions and environmental pollution. Every year solar hot water is used prevents about 1 ton of CO2 emissions compared to gas hot water. Going solar for your domestic hot water is an impactful way to reduce your home’s carbon footprint.
Reduced Utility Bills
The free solar energy harnessed by solar hot water cuts your bills for gas, electricity or other hot water fuels. As utility costs rise over time, bill savings increase. Solar hot water acts as a hedge against inflation on energy prices.
Increased Home Value
Adding solar hot water boosts your home’s value. This system upgrade demonstrates commitment to sustainability and energy efficiency. Solar energy systems are in high demand and increase resale value.
Backup Energy Source
For homes with both solar PV and solar hot water, the hot water acts as a backup energy supply. If a blackout or emergency occurs, the hot water system can continue to provide domestic hot water using power from the sun.
Reduced Maintenance
Solar hot water systems have very low maintenance requirements, and avoid the need to occasionally replace gas hot water tanks. Other than occasional inspections and minor upkeep, solar hot water runs reliably with minimal servicing needs.
Tax Credits and Incentives
Don’t forget about claiming the federal solar tax credit, plus any state/local incentives. These discounts on the purchase price help offset the initial cost of going solar for hot water.
Comparing System Types
There are a few different configurations of solar hot water systems to choose from:
Active Systems
Active solar hot water systems use electric pumps to circulate water or heat transfer fluid through the collectors. This allows the collectors to be installed in more optimal roof or ground locations for capturing solar radiation. Active systems are more efficient, but also more complex and costly upfront.
Passive Systems
Passive systems rely on thermosyphoning to move water through the collectors without pumps or controls. As water in the collector heats up, it naturally rises into the tank above. Cooler water in the tank then moves down to the bottom of the collector, creating a continuous circulation loop. Passive systems are extremely simple and reliable, but do not allow for remote collector placement.
Direct Circulation vs Indirect Circulation
Direct circulation systems pump potable water directly through the collectors. Indirect circulation systems use a heat transfer fluid through the collectors to protect the potable water from temperature extremes. Direct circulation is simpler, while indirect is better for cold climates.
Drainback Systems
Drainback systems drain water from the collectors and piping when not actively heating and circulated. This prevents overheating and stagnation. Drainback systems are more complex and costly, but can also be the most efficient design.
Batch Heater Systems
Batch heaters consist of solar collectors connected directly to a hot water storage tank. No pumps are used. Simple thermosyphoning provides circulation when the sun shines. Batch heaters are one of the lowest cost and simplest solar hot water systems.
Factors Affecting Performance
Proper design and installation are key to maximizing solar hot water system performance. Here are some important factors to consider:
Collector Type and Size
Larger, higher efficiency collectors will harness more heat and maximize solar contribution. Evacuated tube and copper absorber plate collectors are good choices. Correctly sizing the collectors for your household’s hot water demand is crucial.
Collector Orientation and Angle
Collectors should face true south for maximum exposure. The tilt angle should be equal to your latitude to optimize year-round solar absorption.
Insulated Piping
Well insulated piping prevents heat losses between collectors, tanks, and points of use. Foam rubber or other insulation rated for outdoor use is ideal.
Storage Tank Size
Larger tanks store more preheated water. But excessive capacity wastes money and energy keeping unneeded water hot. Accurate storage tank sizing for daily usage helps efficiency.
Cold Climate Design
In cold climates, indirect systems, glycol antifreeze, and drainback designs prevent freezing and damage. This keeps the system operating all winter long.
Building Integration
Roof-mounted collectors with shorter pipe runs to storage tanks improve efficiency. Minimal shade from trees or other objects is important as well. Integrating the system design with the home’s layout and architecture maximizes performance.
Water Temperature Settings
Lower water temperature settings (120°F) reduce losses and let the system operate more efficiently. Dishwashers and washing machines often don’t need very hot water.
Backup Heating Source
A backup heating source tied into the storage tank, like electric or gas heating, helps provide sufficient hot water on cloudy days or high demand periods. This ensures reliable service year-round.
Conclusion
Investing in solar hot water is an excellent way to realize long-term savings on monthly bills while reducing environmental impact. When properly designed and installed for your household size, solar hot water can be a cost effective alternative to gas and electric hot water heating. Take advantage of available tax credits and incentives to maximize the return on your investment in clean, renewable solar energy for domestic hot water.