MoneySavingExpert Chair, Martin Lewis · Editor, Marcus Herbert

# Going from Coal to Air Heat Source Pump and PV's using ECO4 grant scheme

• Posts: 47 Forumite
Financial
Generation
The system is expected to generate 3399 kWh per year
the 25 year term of this fnancial projection the total
generation is expected to be 79867 kwh, of which 28654 kWh
will be consumed on site and 51212 kWh exported.
Payback
After adjusting projected costs and benefts for infation, and
applying a discount rate of 4%, the initial system cost of £0.01
is expected to be recouped after 25+ years.
Net Present Value
The total present value of future benefts and costs, using a
discount rate of 4% per year, is £17,216.57. The cost of the PV
system is £0.01. The net present value of the project is
therefore £17,216.56. A positive net present value is a good
indication that the project is fnancially worthwhile.
IRR
The Internal Rate of Return is a useful measure for comparing
the relative proftability of investments.
Disclaimer
Our fnancial model calculates the benefts of a solar PV installation (such as savings in
electricity, or payments for exported electricity) and costs (the initial purchase cost, and
any future maintenance costs if entered), over the projected lifespan of the system.
Values are corrected for infation, system degradation, and discount rate - a measure
that accounts for the fact that a promise of a monetary sum in the distant future is
usually considered less valuable than the promise of the same sum in the near future.
A model is only as accurate as the assumptions it makes. You should consider whether
the values chosen are appropriate for your situation. There are many variables that
dictate the fnancial return of a solar installation and we cannot forecast how they may
change in the future. This fnancial projection shows a likely scenario for future fnancial
returns. Actual returns may vary signifcantly from this forecast.
Assumptions
Infation rate 2%
Cost of electricity £0.5 /kWh
System size 4 kWp
Discount rate 4%
Projection length 25 years
increases with infation
80
MWh
25+
years
£17216.
56
N/A
%
Income and savings
The projected income from the system
over the project lifetime in payments
for generated and exported electricity,
along with electricity savings, are
shown in the table and graph below.
These fgures assume an infation rate
of 2 percent.
Export payments
Electricity savings
Total
Year 1 329 614 944
Year 2 334 623 958
Year 3 339 633 972
Year 4 344 642 986
Year 5 349 652 1001
Year 6 355 661 1016
Year 7 360 671 1031
Year 8 365 681 1047
Year 9 371 691 1062
Year 10 376 702 1078
Year 11 382 712 1094
Year 12 388 723 1110
Year 13 393 734 1127
Year 14 399 745 1144
Year 15 405 756 1161
Year 16 411 767 1178
Year 17 417 778 1196
Year 18 424 790 1213
Year 19 430 802 1232
Year 20 436 814 1250
Year 21 443 826 1268
Year 22 449 838 1287
Year 23 456 851 1307
Year 24 463 863 1326
Year 25 470 876 1346
Total Export Payments £9889 over 25 years
Electricity savings £18444 over 25 years
0
200
400
600
800
1000
1200
1400
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
The bottom line
The table and graph below show the
discounted costs for the project
(including the initial capital required for
the installation), against the total
discounted benefts from income and
savings on electricity bills.
The system does not pay for itself in
the 25 years of this fnancial projection.
Discounted benefts
Cumulative benefts
Discounted costs
Cumulative costs
Cashfow
Year 1 925 925 0 0 925
Year 2 901 1826 0 0 1826
Year 3 878 2704 0 0 2704
Year 4 855 3559 0 0 3559
Year 5 833 4392 0 0 4392
Year 6 812 5204 0 0 5204
Year 7 791 5995 0 0 5995
Year 8 771 6766 0 0 6766
Year 9 751 7517 0 0 7517
Year 10 732 8249 0 0 8249
Year 11 713 8962 0 0 8962
Year 12 695 9656 0 0 9656
Year 13 677 10333 0 0 10333
Year 14 659 10992 0 0 10992
Year 15 642 11634 0 0 11634
Year 16 626 12260 0 0 12260
Year 17 610 12870 0 0 12870
Year 18 594 13464 0 0 13464
Year 19 579 14043 0 0 14043
Year 20 564 14607 0 0 14607
Year 21 549 15156 0 0 15156
Year 22 535 15692 0 0 15692
Year 23 522 16213 0 0 16213
Year 24 508 16721 0 0 16721
Year 25 495 17217 0 0 17217

• Posts: 47 Forumite
Self consumption
We model here the performance of a solar PV system over the course
of a year, using high resolution minute-by-minute generation data for a
typical PV system and consumption data for a typical house, and
calculating the fow of energy from the solar panels to the house
during the day, and from the grid back to the house at night.
We provide yearly profles of generation, consumption and import /
export, along with detailed profles for a typical spring day.
Consumption
Electricity consumed in the
property each year
3900 kWh Generation
Electricity generated by
the PV array each year
3398 kWh
Self consumption
Proportion of PV
generation used in the
property
36 % Independence
Proportion of electricity
consumption provided by
PV
31 %
Import / Export
Electricity import / export
each year from the
property
• Posts: 47 Forumite
Performance Summary
A. Installation data
Installed capacity of PV system - kWp (stc) 4 kWp
Orientation of the PV system - degrees from South See individual inputs
Inclination of system - degrees from horizontal See individual inputs
Postcode region 1
B. Performance calculations
kWh/kWp (Kk) See individual inputs
Shade factor (SF) See individual inputs
Estimated output (kWp x Kk x SF) 3399 kWh
Important Note: The performance of solar PV systems is impossible to predict with certainty due to the
variability in the amount of solar radiation (sunlight) from location to location and from year to year. This
estimate is based upon the standard MCS procedure is given as guidence only for the frst year of
generation. It should not be considered as a guarantee of performance.
Shading will be present on your system that will reduce its output to the factor stated. This factor was
calculated using the MCS shading methodology and we believe that this will yield results within 10% of
the actual energy estimate stated for most systems.
• Posts: 47 Forumite
Not very good with technology so have provided the basic data. Not sure what questions to ask. What stands out for you?
• Posts: 1,342 Forumite
• Posts: 13,822 Forumite
Pec123 said it was an ECO4 installation, so free of charge to the householder.
N. Hampshire, he/him. Octopus Go elec & Tracker gas / Shell BB / Lyca mobi. Ripple Kirk Hill member.
2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 3.6kw inverter. 30MWh generated, long-term average 2.6 Os.
Taking a break, hope to be back eventually.
Ofgem cap table, Ofgem cap explainer. Economy 7 cap explainer. Gas vs E7 vs peak elec heating costs.
• Posts: 1,342 Forumite
QrizB said:
Pec123 said it was an ECO4 installation, so free of charge to the householder.
Just making sure, more of a rhetorical question really

So then, whether you are any good with technology or not, I can't see anything not to like!

I would be more than happy to accept what I was offered.
• Posts: 2,296 Forumite
Pec123 said:
1952 semi detached three bedroom house 116sqm, they will be putting insulation in, coal heating/water with a Rayburn.
What insulation is being installed? A house from that date might be brick cavity walls, plastered on the hard. Is it a suspended timber floor downstairs, or concrete? Window presumably already replaced from original.
• Posts: 47 Forumite
Qyburn said:
Pec123 said:
1952 semi detached three bedroom house 116sqm, they will be putting insulation in, coal heating/water with a Rayburn.
What insulation is being installed? A house from that date might be brick cavity walls, plastered on the hard. Is it a suspended timber floor downstairs, or concrete? Window presumably already replaced from original.
I'll have to find out insulation. In the eaves. We already have brick foam filled cavity walls. Suspended timber floor downstairs. Windows already replaced with the vented kind,
• Posts: 47 Forumite
The options we have been given:

1. *HIB* Longi HiMo5 400W All Black Mono solar panel 10
SolaX X1-3.6T 1ph (inc WiFi dongle) inverter

2.  Longi 425w white backsheet solar panel 10
Growatt MIN 3600 TL-X Dual MPPT 1ph (inc DC isolator) inverter

Which is more valuable?

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