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Anyone using a solar voltaic array to power up an electric hot water heater?
Solar to heat hot water
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RobertN
Super Member
We have solar over electric hot water.
Ours has a recirculating pump that pumps glycol mixture thru thre panels on the roof. The pump is powered by a small PV panel. It's a closed loop system.
The water heater also has a electric element for cloudy days.
Ours has a recirculating pump that pumps glycol mixture thru thre panels on the roof. The pump is powered by a small PV panel. It's a closed loop system.
The water heater also has a electric element for cloudy days.
This sounds like a "thermal" set up Robert. I was curious if it could be done and how many panels it would take to power the water heater with a voltaic system. You wouldn't know the wattage of your heater? Maybe with that info I could do some math and figure it out to see if it's feasible..
dragoneggs
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Before you invest in any solar system, check your locale to be sure it is even close to the return on investment. I don't know about RI but here in Washington, it is pretty much impossible to justify unless you don't have access to electricity from the grid.
quicksandfarmer
Elite Member
I have a long post here arguing that solar electric is more cost-effective than solar thermal. This is particularly true where net metering is the law (as in Rhode Island) and if you use a heat pump water heater.
The more complicated question is whether solar is price competitive with other energy sources. That is determined by the cost of solar, including subsidies, and the cost of alternatives. In most places where solar is popular there are extensive local subsidies. To my knowledge there are no longer any local subsidies in Rhode Island, just the federal 30% tax credit for your primary residence. There is a sales tax exemption and a local property tax exemption.
I recently had a solar electric system installed on a house I own in another state. The installed cost was $690 per 250 watt panel, which included everything. The panels cost about $250 each, the fittings are probably another $250 so you could save a significant amount by doing the installation yourself. Each panel produces about 335 kwh of electricity a year. Rhode Island has expensive electricity, I think I'm paying $.15/khw, so that's $50 worth of electricity a year per panel.
With an installed cost of $690, the federal tax credit of 30% gives a net cost of $483. At $50 per year that's just under a ten-year payback period. That's not great, but it's not outrageous. It also means you're protected against electric rate hikes, odds are the price of electricity is going up over the next ten years so the actual payback is shorter.
If you can reduce the installation cost the payback shortens. At $500 per panel, net $350 after taxes, the payback is seven years.
The other part of the equation is what are the alternatives to electricity for heating water. We don't have natural gas here, most people use fuel oil, which lately is "wicked high," as they say in the Ocean State. It's controversial, but I believe electricity is cheaper on a year-round basis because of the stand-by costs of running an oil burner outside of the heating season, and I have a heat pump water heater. Propane is even higher than oil. Some use wood to heat water, which is probably the lowest cost option right now, but it's not for me. My dad had coal for a while, he's a flinty New Englander, but not for me either.
So it's worth looking into.
The more complicated question is whether solar is price competitive with other energy sources. That is determined by the cost of solar, including subsidies, and the cost of alternatives. In most places where solar is popular there are extensive local subsidies. To my knowledge there are no longer any local subsidies in Rhode Island, just the federal 30% tax credit for your primary residence. There is a sales tax exemption and a local property tax exemption.
I recently had a solar electric system installed on a house I own in another state. The installed cost was $690 per 250 watt panel, which included everything. The panels cost about $250 each, the fittings are probably another $250 so you could save a significant amount by doing the installation yourself. Each panel produces about 335 kwh of electricity a year. Rhode Island has expensive electricity, I think I'm paying $.15/khw, so that's $50 worth of electricity a year per panel.
With an installed cost of $690, the federal tax credit of 30% gives a net cost of $483. At $50 per year that's just under a ten-year payback period. That's not great, but it's not outrageous. It also means you're protected against electric rate hikes, odds are the price of electricity is going up over the next ten years so the actual payback is shorter.
If you can reduce the installation cost the payback shortens. At $500 per panel, net $350 after taxes, the payback is seven years.
The other part of the equation is what are the alternatives to electricity for heating water. We don't have natural gas here, most people use fuel oil, which lately is "wicked high," as they say in the Ocean State. It's controversial, but I believe electricity is cheaper on a year-round basis because of the stand-by costs of running an oil burner outside of the heating season, and I have a heat pump water heater. Propane is even higher than oil. Some use wood to heat water, which is probably the lowest cost option right now, but it's not for me. My dad had coal for a while, he's a flinty New Englander, but not for me either.
So it's worth looking into.
Raspy
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quick,
Nice post. Another factor that is unknown and not mentioned is the reliability or longevity of the electric solar equipment.
Some failures that get mentioned to me are the collector connectors and the inverters. The inverters are particularly expensive and once out of warrantee, which happens way before payback, you are on your own. The solar companies also try to sell you a maintenance plan for cleaning the glass, etc, that severely cuts into the overall savings. This is optional of course, but probably a lot of folks buy it because they are told the system won't work with dirty glass and it's dangerous to get up on the roof.
One fix for this would be a cost sharing plan where you don't own the system. But these pay back less and I don't know who takes responsibility for the roof.
I can't get very enthused unless the location has very clear weather, good orientation, no shade at all on the system and the homeowners can do the installation themselves.
Solar thermal can have mechanical problems too. A simple design with absolute freeze protection is best.
Nice post. Another factor that is unknown and not mentioned is the reliability or longevity of the electric solar equipment.
Some failures that get mentioned to me are the collector connectors and the inverters. The inverters are particularly expensive and once out of warrantee, which happens way before payback, you are on your own. The solar companies also try to sell you a maintenance plan for cleaning the glass, etc, that severely cuts into the overall savings. This is optional of course, but probably a lot of folks buy it because they are told the system won't work with dirty glass and it's dangerous to get up on the roof.
One fix for this would be a cost sharing plan where you don't own the system. But these pay back less and I don't know who takes responsibility for the roof.
I can't get very enthused unless the location has very clear weather, good orientation, no shade at all on the system and the homeowners can do the installation themselves.
Solar thermal can have mechanical problems too. A simple design with absolute freeze protection is best.
dave1949
Super Star Member
Pricing from the electric utilities is a big future unknown and varies considerably by region as we know from posters around the TBN world.
The basic monthly service connection fee for our area has changed quite a bit. I was paying $8.12 per month--the minimum for being connected--which included the delivery cost for the first 100 kWh's of usage. That was about 3 years ago. Now the minimum is $10.65 per month and covers only the first 50 kWh's per month delivery cost. That is effectively about doubling the cost of the first 100 kWh's and it was purposely aimed at low usage people like those who have grid-tied systems.
My current pricing (grid delivery & generated supply) is:
Electricity grid delivery service up to 50 kWh $10.65
-----------------------------------over 50 kWh $0.063264 per kWh
Electricity generation supply cost is $0.075603 per kWh for all kWh used.
For grid-tied customers the billing is applied to the 'IN' meter reading, then a credit against that is calculated based on the 'OUT' meter reading. 'OUT' is what my system sent into the grid. I am credited $0.1388 per OUT kWh; the sum of the supplier charge and the rate above 50 kWh for the delivery charge. If my OUT exceeds my IN, those kWh's are banked at the current per kWh price for use within the next 12 months after which they expire.
I wouldn't expect utility rates to remain stable. I think the current natural gas boom will act to curtail increases until the global market utilization expansion raises the demand for natural gas. What various countries decide to do or not do about their carbon footprints is anyone's guess. What they actually do may/will be different than what they set as a policy goal to do.
The basic monthly service connection fee for our area has changed quite a bit. I was paying $8.12 per month--the minimum for being connected--which included the delivery cost for the first 100 kWh's of usage. That was about 3 years ago. Now the minimum is $10.65 per month and covers only the first 50 kWh's per month delivery cost. That is effectively about doubling the cost of the first 100 kWh's and it was purposely aimed at low usage people like those who have grid-tied systems.
My current pricing (grid delivery & generated supply) is:
Electricity grid delivery service up to 50 kWh $10.65
-----------------------------------over 50 kWh $0.063264 per kWh
Electricity generation supply cost is $0.075603 per kWh for all kWh used.
For grid-tied customers the billing is applied to the 'IN' meter reading, then a credit against that is calculated based on the 'OUT' meter reading. 'OUT' is what my system sent into the grid. I am credited $0.1388 per OUT kWh; the sum of the supplier charge and the rate above 50 kWh for the delivery charge. If my OUT exceeds my IN, those kWh's are banked at the current per kWh price for use within the next 12 months after which they expire.
I wouldn't expect utility rates to remain stable. I think the current natural gas boom will act to curtail increases until the global market utilization expansion raises the demand for natural gas. What various countries decide to do or not do about their carbon footprints is anyone's guess. What they actually do may/will be different than what they set as a policy goal to do.
