SIMPLE ECONOMIC MODEL – HOUSEHOLD SOLAR + BATTERY

Released by Chris Cooper 6/5/2015, under the Creative Commons Licence (CC BY-NC Attribution-Non Commercial).  Major revision by Roger Dargaville, March 2019
The author offers no guarantees about the accuracy of this model, nor liability for its use.

PLEASE READ  – MODEL ASSUMPTIONS + LIMITATIONS YOU SHOULD KNOW ABOUT
1. All costs are $AU unless stated
2. Key inputs are in Yellow
3. Information on some of the key inputs is still unclear. Any uncertainty is discussed in the cell comments. 
4. In the interests of keeping this model simple and easy to use:
 a. Hourly demand intervals used
 b. The battery is automatically topped up by grid between 2pm and 3pm unless already topped up. If a relatively small solar PV system is installed, this can lead to a charge rate which exceeds the Powerwall’s continuous power rating during this time.
 c. There is no assumed degradation of solar output or battery round-trip efficiency over time
 d. The model calculates the impact of solar and battery on an average day of generation and consumption. YEARLY EXPRAPOLATIONS (IN GREY) ARE BASED ON THE ‘AVERAGE DAY’ AND SHOULD THEREFORE BE USED ONLY AS AN ‘UPPER BOUND’ GUIDE OF THE POTENTIAL BENEFITS. Simulations have not been conducted for variations in daily sunshine and electricity consumption as doing so would add signification complexity to the calculator.

KEY MODEL ASSUMPTIONS

Household load profile type (select)

 ‘Stay at home’ steady daytime load

OUTPUT

Daily household energy use

15

kWh

Net annual benefit

0.00

Solar PV system size

0

kW

* inverter size is limited to 5kw so output greater than 5kW will be curtailed

Battery size (select)

0

kWh

Installed cost for battery system

0

$AUD

Location (select)

Melbourne

TECHNICAL + ECONOMIC INPUTS

ELECTRICITY PRICES

Flat

ToU

Tariff type

ToU

If ToU, model uses data in column S of the power flow data

Flat Electricity tariff

0.25

$/kWh

Solar export credit

0.1

$/kWh

Tariff is  limited to systems with 5kW and below (bigger than 5kW, no fiT)

SOLAR

Capital costs

1.002

$/W

This is based on the city chosen and data

Total installed cost

0

$

Average Solar Generation/kWp

3.6

KWh/kWp (based on location)

1.571428571

BATTERY

$/kWh ($AU)

0

$/KWh

Total installed cost ($AU)

0

Includes mark-up and exchange rate

Extended warranty cost $/kWh

0

$/kWh of capacity

Total extended warranty cost

0

$

Annual maintenance cost

0

$/kWh/yr

Max Depth of Discharge

100%

%  CHECK COMMENT BEFORE SELECTING

0.7

Usable capacity

0

kWh

1

Minimum state of charge

0

kWh

Round trip efficiency

92%

ECONOMIC INPUTS

Interest/discount rate

6%

Levelised term / technology life

15