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opinion:frater_secessus:controllers_and_dollars_per_watt

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fixme

NOTE: this is a rough draft. Costs based on prices on Amazon of Renogy controllers where available.

cost analysis of small controller / panel combinations

For about the same price a second solar panel can give 100% more power. Above about 300 to 400 watts MPPT is financially advantageous.

A fair rule of thumb. It gets distorted a bit at 200w because PWM controllers can't be overpaneled, requiring an upgrade there.

I ran some numbers, using Renogy gear where possible:

general conclusion

The general pattern is that MPPT typically makes more power in absolute terms, and PWM/shunt make more power per dollar spent.

raw cost

In terms of initial investiment, from least expensive to most expensive

  1. shunt + poly panels. Shunts have similar performance characteristics to PWM but are simpler. Smart charging may not be available. They tend to be very cheap, $1 per rated amp.
  2. shunt + mono panels (not recommended due to low Imp)
  3. PWM + poly panels
  4. PWM + mono panels (not recommended due to low Imp)
  5. overpaneled MPPT + whatever panels are cheapest. In this model a slightly undersized (and therefore less expensive) controller is used.1)
  6. MPPT + whatever panels are cheapest

Morning, ideal

(12.1v), 50deg F, perfect insolation

ranked by output

  1. 20A MPPT 200W poly/mono, 174.80W @ $1.65/W. $289.
  2. 20a PWM 200w poly 125.89W @ $1.99/W. $250.
  3. 10A MPPT 200w mono/poly, 121W @ $2.16/W. $261.
  4. 10a MPPT 100W mono/poly 87.4W @ $1.84/W. $161.
  5. 10a PWM 100W poly 62.94W @ $1.82/W. $115.

ranked by $/watt

  1. 20A MPPT 200W poly/mono, 174.80W @ $1.65/W. $289.
  2. 10a PWM 100W poly 62.94W @ $1.82/W. $115.
  3. 10a MPPT 100W mono/poly 87.4W @ $1.84/W. $161.
  4. 10a PWM 100W mono 59.25W @ $1.93/W. $115.
  5. 20a PWM 200w poly 125.89W @ $1.99/W. $250.

Morning, 75% insolation

(12.1v), 75% insolation - I did not calculate mono on these, as PWM performs better on poly and MPPT doesn't care.

ranked by output:

  1. 20A MPPT 200w mono/poly, 131.1W @ $2.20/W. $289.
  2. 10A MPPT 200w mono/poly, 121W @ $2.16/W. $261.
  3. 20A PWM 200w poly 94.42W @ $2.76/W. $250.
  4. 10 MPPT 100w mono/poly 65.55W @ $2.46/W. $161.
  5. 10A PWM 100w poly, 47.21W @ $2.42/W. $115.

ranked by $/watt.

  1. 10A MPPT 200w mono/poly, 121W @ $2.16/W. $261.
  2. 20A MPPT 200w mono/poly, 131.1W @ $2.20/W. $289.
  3. 10A PWM 100w poly, 47.21W @ $2.42/W. $115.
  4. 10 MPPT 100w mono/poly 65.55W @ $2.46/W. $161.
  5. 20A PWM 200w poly 94.42W @ $2.76/W. $250.

Afternoon, ideal

(14.6v), 70deg F, perfect insolation -

ranked by output:

  1. 20A MPPT 200w mono/poly 165.27W @ $1.75/W. $289.
  2. 20A PWM 200w poly 164.10W @ $1.52/W. $250.
  3. 20A PWM 200w mono 154.47W @ $1.62/W. $250.
  4. 10A MPPT 200w mono/poly 146.0W @ $1.78/W. $260.
  5. 10A MPPT 100W mono/poly 82.63W @ $1.95/W. $161.
  6. 10A PWM 100w poly 82.05W @ 1.39/W. $115.
  7. 10A PWM 100w mono 77.23W @ $1.48/W. $115.

ranked by $/watt

  1. 10A PWM 100w poly 82.05W @ $1.39/W. $115.
  2. 10A PWM 100w mono 77.23W @ $1.48/W. $115.
  3. 20A PWM 200w poly 164.10W @ $1.52/W. $250.
  4. 20A PWM 200w mono 154.47W @ $1.62/W. $250.
  5. 20A MPPT 200W mono/poly 165.27W @ $1.75/W. $289.
  6. 10A MPPT 200w mono/poly 146.0W @ $1.78/W. $260.
  7. 10A MPPT 100W mono/poly 82.63W @ $1.95/W. $161.

Afternoon, 75% insolation

(14.6v), 75% insolation -

ranked by output:

  1. 20A MPPT 200W mono/poly 125.93W @ $2.29/W. $289
  2. 10A MPPT, 200w mono/poly 125.93W @ $2.07/W. $261.2)
  3. 20A PWM, 200w poly, 123.08W @ $2.12/W. $250.
  4. 10A MPPT, 100w mono/poly, 61.99w @ $2.60/W. $161.
  5. 10A PWM, 100w poly, 61.54 @ $1.62/W. $115.

ranked by $/watt

  1. 10A PWM, 100w poly, 61.54 @ $1.62/W. $115.
  2. 10A MPPT, 200w mono/poly 125.93.0W @ $2.07/W. $261.
  3. 20A PWM, 200w poly, 123.08W @ $2.12/W. $250.
  4. 10A MPPT, 100w mono/poly, 61.99w @ $2.60/W. $161.
1)
Shunt and PWM cannot be overpaneled safely as they have no ability to reduce their current throughput
2)
same output as 20A controller; panel yield is less than 10A
opinion/frater_secessus/controllers_and_dollars_per_watt.txt · Last modified: 2021/06/26 14:33 by frater_secessus

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