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Solar System Size & ROI Calculator

Enter your monthly usage, pick your inverter and battery, and we'll size the system, cost it, finance it, and project your 20-year savings — instantly.

Step 1 · Energy Usage Input

Calculation method

Average monthly usage (kWh)

kWh

Day vs night usage split — 50% day / 50% night

Price / kWh

Estimated annual energy price increase

Derived monthly consumption: 1,200 kWh

System Spec Requirements

For near off-grid setup

Average daily energy requirement

39.4 kWh

Required inverter size & solar capacity

7.17 kWp

Required battery storage capacity

19.71 kWh

Recommended solar panels (610W)

12 panels

Province (optional preset)

Peak Sun Hours (PSH)

hrs/day

Step 2 · System Builder

Select inverter

Min required: 7.2 kW continuous

Select battery

Min usable required: 19.7 kWh

Usable capacity

11.4 kWh

Round-trip eff.

95%

Depth of discharge

95%

Solar panel quantity (610W)

Roof type

Add estimated installation, consumables & COC

Financing Calculator

Prime rate

Loan repayment period

months

Deposit

Average repayment

R 3 184 /mo

Total cost with financing

R 191 030

Estimated system costs

Inverter priceR 21 430

Battery priceR 27 900

Panel priceR 26 400

Mounting structureR 8 640

Major components (excl)R 84 370

Installation & servicesR 22 800

Switch gear, safety & cablingR 18 000

Total excl VATR 125 170

Total incl VATR 143 946

Your system summary

Estimated total cost incl

R 143 946

Estimated repayment if financed

R 3 184 /mo

Payback period

3.0 yrs

Grid independence

77%

Annual bill before solar

R 54 000

Annual bill after solar

R 12 166

Annual savings (Y1)

R 41 834

Savings over 20 years

R 4 285 596

Major component

Sunsynk 8kW Hybrid 48V (1-Phase)

8 kW · 1-phase

Solar panels peak output

7.32 kWp

Daily solar generation (Y1)

40.3 kWh/day

Major component

Deye 12kWh SE-F16 LiFePO4

12 kWh nominal · DoD 95% · RTE 95%

Usable capacity

11.4 kWh

Energy stored (Y1)

11.4 kWh/day

Estimated costs, savings & ROI breakdown

20-year financial model

Yr	R/kWh	Annual solar (kWh)	Daily solar	Excess/day	Battery (kWh)	Stored/day	Night cover	Night grid/day	Total grid/yr	Bill after (R)	Annual saving (R)	Cumulative (R)	Indep.
1	R3.75	14,705	40.3	9.1	11.4	11.4	55%	8.9	3,244	12,166	41,834	41,834	77%
2	R4.31	14,631	40.1	8.9	11.4	11.4	55%	8.9	3,244	13,991	48,109	89,942	77%
3	R4.96	14,558	39.9	8.7	11.4	11.4	55%	8.9	3,244	16,090	55,325	145,268	77%
4	R5.70	14,485	39.7	8.5	11.4	11.4	55%	8.9	3,244	18,503	63,624	208,891	77%
5	R6.56	14,413	39.5	8.3	11.4	11.4	55%	8.9	3,244	21,279	73,167	282,059	77%
6	R7.54	14,341	39.3	8.2	11.4	11.4	55%	8.9	3,244	24,471	84,143	366,201	77%
7	R8.67	14,269	39.1	8.0	11.4	11.4	55%	8.9	3,244	28,141	96,764	462,965	77%
8	R9.98	14,198	38.9	7.8	11.4	11.4	55%	8.9	3,244	32,363	111,279	574,244	77%
9	R11.47	14,127	38.7	7.6	11.4	11.4	55%	8.9	3,244	37,217	127,970	702,214	77%
10	R13.19	14,056	38.5	7.4	11.4	11.4	55%	8.9	3,244	42,799	147,166	849,380	77%
11	R15.17	13,986	38.3	7.2	11.4	11.4	55%	8.9	3,244	49,219	169,241	1,018,621	77%
12	R17.45	13,916	38.1	7.0	11.4	11.4	55%	8.9	3,244	56,602	194,627	1,213,248	77%
13	R20.06	13,847	37.9	6.8	11.4	11.4	55%	8.9	3,244	65,093	223,821	1,437,068	77%
14	R23.07	13,777	37.7	6.6	11.4	11.4	55%	8.9	3,244	74,857	257,394	1,694,462	77%
15	R26.53	13,708	37.5	6.4	11.4	11.4	55%	8.9	3,244	86,085	296,003	1,990,465	77%
16	R30.51	13,640	37.3	6.2	11.4	11.4	55%	8.9	3,244	98,998	340,404	2,330,869	77%
17	R35.09	13,572	37.2	6.0	11.4	11.4	55%	8.9	3,244	113,847	391,464	2,722,333	77%
18	R40.35	13,504	37.0	5.9	11.4	11.4	55%	8.9	3,244	130,925	450,184	3,172,517	77%
19	R46.41	13,436	36.8	5.7	11.4	11.4	55%	8.9	3,244	150,563	517,711	3,690,228	77%
20	R53.37	13,369	36.6	5.5	11.4	11.4	55%	8.9	3,244	173,148	595,368	4,285,596	77%

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