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

  - [[electrical:solar:shunt_tweaking|shunt]] + poly panels.  Shunts have similar performance characteristics to PWM but are simpler.  [[electrical:12v:charging|Smart charging]] may not be available. They tend to be very cheap, $1 per rated amp.
  - shunt + mono panels  (not recommended due to low Imp)
  - [[electrical:solar:pwm_tweaking|PWM]] + poly panels
  - PWM + mono panels (not recommended due to low Imp)
  - [[electrical:solar:overpaneling|overpaneled]] MPPT + whatever panels are cheapest.  In this model a slightly undersized (and therefore less expensive) controller is used.((Shunt and PWM cannot be overpaneled safely as they have no ability to reduce their current throughput))
  - MPPT + whatever panels are cheapest

===== Morning, ideal =====


(12.1v), 50deg F, perfect insolation 

ranked by **output**

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


ranked by **$/watt**

  - 20A MPPT 200W poly/mono, 174.80W  @ **$1.65/W**.  $289.
  - 10a PWM 100W poly 62.94W @ **$1.82/W**.  $115.
  - 10a MPPT 100W mono/poly 87.4W @ **$1.84/W**.  $161.
  - 10a PWM 100W mono 59.25W @ **$1.93/W**.  $115.
  - 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**:  
 
  - 20A MPPT 200w mono/poly, **131.1W** @ $2.20/W.  $289.
  - 10A MPPT 200w mono/poly, **121W** @ $2.16/W.  $261.
  - 20A PWM 200w poly **94.42W** @  $2.76/W.  $250.
  - 10 MPPT 100w mono/poly **65.55W**  @ $2.46/W.  $161.
  - 10A PWM 100w poly, **47.21W**  @ $2.42/W.  $115.

ranked by **$/watt**.  

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


===== Afternoon, ideal =====


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


ranked by **output**:

  - 20A MPPT 200w mono/poly **165.27W** @ $1.75/W.  $289.
  - 20A PWM 200w poly **164.10W** @ $1.52/W.  $250.
  - 20A PWM 200w mono **154.47W** @ $1.62/W.  $250.
  - 10A MPPT 200w mono/poly **146.0W** @ $1.78/W.  $260.
  - 10A MPPT 100W mono/poly **82.63W** @ $1.95/W.  $161.
  - 10A PWM 100w poly **82.05W** @ 1.39/W.  $115.
  - 10A PWM 100w mono **77.23W** @ $1.48/W.  $115.

ranked by **$/watt**

  - 10A PWM 100w poly 82.05W @ **$1.39/W**.  $115.
  - 10A PWM 100w mono 77.23W @ **$1.48/W**.  $115.
  - 20A PWM 200w poly 164.10W @ **$1.52/W**.  $250.
  - 20A PWM 200w mono 154.47W @ **$1.62/W**.  $250.
  - 20A MPPT 200W mono/poly 165.27W @ **$1.75/W**.  $289.
  - 10A MPPT 200w mono/poly 146.0W @ **$1.78/**W.  $260.
  - 10A MPPT 100W mono/poly 82.63W @ **$1.95/W**.  $161.

===== Afternoon, 75% insolation =====


(14.6v), 75% insolation - 



ranked by **output**:

  - 20A MPPT 200W mono/poly **125.93W** @ $2.29/W. $289
  - 10A MPPT, 200w mono/poly **125.93W** @ $2.07/W.  $261.((same output as 20A controller;  panel yield is less than 10A))
  - 20A PWM, 200w poly, **123.08W**  @ $2.12/W.  $250.
  - 10A MPPT, 100w mono/poly, **61.99w**  @ $2.60/W.  $161.
  - 10A PWM, 100w poly,  **61.54** @ $1.62/W.  $115.

ranked by **$/watt**

  - 10A PWM, 100w poly,  61.54 @ **$1.62/W**.  $115.
  - 10A MPPT, 200w mono/poly 125.93.0W @ **$2.07/W**.  $261.
  - 20A PWM, 200w poly, 123.08W  @ **$2.12/W**.  $250.
  - 10A MPPT, 100w mono/poly, 61.99w  @ **$2.60/W**.  $161.