Is this a reasonable solar bid? — and other questions
I got my first solar bid today, from Consolidated Solar Technologies. For a 3.2 kW ground-mount array in Albuquerque, New Mexico, the total cost before the federal tax credit is $16,300, and $11,410 after the credit. This works out to $3.56/watt.
One thing I worry about is that their calculator shows a higher projected output than PVWatts does. Their tool showed 6,500 kWh yearly, but PVWatts shows 5,844 kWh. This is supposed to be a net-zero-enabling array, so I don’t want to underproduce. I’m using 6,500 kWh for my yearly usage
Another concern: my electrical panel has four slots left, and the estimator told me they generally need four slots to interconnect. This is an issue because I have yet to add the 240v breaker for an electric heat pump, which would leave me with only two slots–not enough.
Finally, I worry that my estimating is off; I haven’t yet installed the heat pump and am only estimating its use. Last year was really cold and we used 176 therms (delivered, not purchased–accounting for 80% efficient equipment) to heat the home for the whole heating season. That translates into 17,600,000 BTUs. At a COP of 3.5, that requires 1,474 kWh for the season. I figure 3.5 is reasonable since much of the season features sunny daytime temperatures that rise into the 40s and 50s where the unit operates at high efficiency, and we can be trusted to keep the thermostat low at night and only let the machine turn on once outside temperatures have risen a bit (also the outdoor unit will be on the east side and getting bathed in sunlight most mornings). Summer AC usage will be much lower since we already have a swamp cooler that works fine most of the time.
So here are my questions for you guys:
- Does $3.56/watt sound reasonable?
- Should I trust PVWatts, or their calculator?
- Are their installers/companies/equipment that can use only two slots in an electrical panel?
- Is my estimate of heat pump electricity usage sane?
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