Tom Solar homeowner knowledge centre
31 solar questions answered in depth.
No sales-script shortcuts.
These guides help Scottish homeowners understand what they are actually buying — from the physics inside a solar cell to roof suitability, batteries, inverters, grid connections, electric vehicles, heat pumps, warranties and payback calculations.
Find your subject
Start with the part you are trying to understand.
The library is organised around eight subjects homeowners commonly need to understand before choosing a solar or battery system.
The complete library
Practical answers, one subject at a time.
Some questions can be answered in a paragraph. Others deserve diagrams, calculations and a proper explanation. These are the questions that repeatedly come up when homeowners are deciding what to install.
Costs, quotes, savings & payback
Understand why apparently similar proposals can produce dramatically different prices, savings claims and predicted returns.
Quotes
How do I compare completely different solar quotes?
Compare equipment, design, warranties, assumptions and total value rather than simply choosing the final price.
Read guide →Savings & ROI
Why are solar payback figures so different?
See how self-consumption, tariffs, inflation, finance and other assumptions can transform the apparent return.
Read guide → New guideInvestment decision
Are solar panels actually a good investment?
Test roof suitability, system sizing, payback and risk before deciding whether a proposed solar system genuinely makes sense for your home.
Read guide → New guideBills & payback
How does my monthly electricity bill affect solar payback?
Understand why higher usage can shorten payback—and why the monthly payment alone cannot prove the return.
Read guide →Solar panels & generation
Understand how panels produce electricity, how much solar you may need and what Scottish weather really means for generation.
System sizing
How many solar panels do I actually need?
Panel count should follow electricity demand, usable roof space, orientation and future electrification.
Read guide → Visual guideSolar science
How does a solar panel actually work?
Follow sunlight from the silicon solar cell through DC generation, the inverter and into the electricity used by your home.
Read guide → Visual guideScottish weather
Do solar panels work in winter and cloudy weather?
Understand diffuse light, shorter days, low winter sun, temperature effects and why cloudy does not mean zero generation.
Read guide →Roofs, orientation, shading & installation
Roof direction, usable area, shading and fixing methods can change both the design and the economics of a solar installation.
Roof orientation
Are north-facing solar panels worth installing?
North-facing does not automatically mean useless. Learn when the extra generation can still make financial sense.
Read guide → Visual guideRoof fixing
Can solar panels damage my roof or cause leaks?
See how roof hooks are fixed, how tiles are reinstated and why a properly designed installation should remain weather-tight.
Read guide → New guideGround mounting
Ground-mounted solar on uneven land: ballast, posts or ground screws?
Compare foundations, site evidence, slope, soil, drainage and planning before choosing a structure.
Read guide →Batteries & energy storage
Battery capacity should follow household demand, solar generation, electricity tariffs and the amount of energy you actually need to move.
Battery sizing
What size solar battery do I actually need?
Storage should be sized around the electricity you actually want to move through the day.
Read guide →Battery capacity
Do I really need two solar batteries?
A second battery can be valuable — or unnecessary. The answer depends on usable capacity, tariffs and household demand.
Read guide → New guideBattery retrofit
Can I add a battery to my existing solar panels?
Compare AC coupling and hybrid conversion, FIT implications, DNO requirements, backup options and retrofit economics.
Read guide → New guideBattery lifespan
How long do solar batteries last?
Understand calendar ageing, cycles, throughput, capacity retention, warranty limits and realistic replacement planning.
Read guide → Visual guideBackup power
What happens to solar panels during a power cut?
Learn why ordinary grid-connected solar shuts down, how anti-islanding protects the network and what proper battery backup changes.
Read guide → New guideSmart battery tariffs
What is Octopus Charge Pack and is it worth it?
Understand automatic battery control, the current £12 monthly minimum, compatible batteries and what Octopus gets permission to do in return.
Read guide → New guideBattery-only storage
Can a home battery save money without solar panels?
See how tariff shifting works, what losses do to the margin and when the installed price defeats the case.
Read guide →Inverters, optimisers & system design
Panel count is only part of the design. Inverter power, MPPTs, strings, shading and module-level electronics all need to work together.
Inverters
What size solar inverter do I actually need?
Understand inverter power, PV oversizing, strings, MPPTs, batteries and grid limits.
Read guide → Visual guideShading & optimisation
Do I need solar panel optimisers?
Learn when module-level optimisation genuinely helps, what bypass diodes and MPPTs already do, and when extra electronics may add little.
Read guide →Grid connections & electrical supply
Larger solar and battery systems increasingly depend on the capacity, configuration and permissions attached to the property's electrical supply.
Grid connections
What is the difference between G98 and G99?
Learn why 3.68kW matters, when DNO approval is needed and how grid limits affect larger systems.
Read guide →Electrical supply
What is a looped electricity supply?
Understand shared service cables, de-looping and why EV chargers or other low-carbon technologies may uncover the issue.
Read guide →Electrical capacity
Should I upgrade my home to three-phase electricity for solar?
Three-phase can add considerable capability, but it does not automatically guarantee additional solar export capacity.
Read guide → Updated guidePlug-in solar
Plug-in solar is now legal — but is it worth it?
Understand the new 800W Great Britain route, safety requirements, realistic savings and where plug-in solar may genuinely make sense.
Read guide →Tariffs, charging & export
Compare the complete import-and-export arrangement, equipment rules and cheap-rate windows before relying on a headline price.
Tariffs
10 leading UK solar and battery tariffs compared
See which options suit solar, battery-only and EV homes — and why the cheapest overnight rate may not produce the lowest annual bill.
Compare tariffs → New guideTesla Energy & smart batteries
Tesla is coming — but the revolution is already here
See why Tesla's UK supply licence matters, which rivals are already automating batteries and why software compatibility could change what a battery is worth.
Read guide →Battery optimisation
What is Octopus Charge Pack?
Understand compatibility, battery control, the monthly credit and what to check before joining.
Read guide →EVs, heat pumps & home electrification
Electric vehicles and heat pumps can transform household electricity demand — and therefore change the right solar, battery and tariff strategy.
Heat pumps
Is solar worth it with a heat pump?
See how heat loss, seasonal efficiency, winter demand, battery storage and off-peak tariffs change the solar calculation.
Read guide → New calculatorEV ownership costs
Is an EV worth it for a high-mileage driver?
Compare keeping a cheap paid-for petrol car, replacing it with an EV, or adding a used EV for suitable local journeys.
Calculate the real cost →Electric vehicles
Is solar worth it if I have an electric vehicle?
Understand mileage, smart charging, solar surplus, home batteries and why the cheapest charging strategy is not always daytime solar.
Read guide →Warranties, maintenance, lifespan & ownership
A solar system is a long-term purchase. Understand the difference between warranty promises, degradation and genuine useful life.
Lifespan & warranties
How long do solar panels actually last?
Separate product warranty, performance warranty, degradation and the genuine useful life of a solar array.
Read guide → New guideWarranties & protection
What do solar panel warranties actually cover?
Separate product, performance, workmanship, inverter, battery and insurance-backed protection—and see which costs may still be yours.
Read guide → New guideCleaning & maintenance
Do solar panels need cleaning and maintenance?
Learn when cleaning is worthwhile, which checks homeowners can make, the warning signs that need a professional and how to work safely.
Read guide →Make the guidance specific to your home
Want to know whether this applies to your roof?
Find your property on the map and send me the exact roof you want assessed. It gives us a much better starting point than discussing solar in the abstract.
The principle behind the library
The strongest proposal should have the strongest evidence behind it.
A homeowner should not have to decide whether to trust somebody purely because one salesperson sounds more convincing than another.
The useful evidence is measurable:
Roof measurements. Electricity usage. Generation estimates. Heat loss. Battery capacity. Inverter limits. Grid permission. Tariffs. Shading. Assumptions. Warranty terms. Then explain why the proposed system follows from those facts.
Need an answer about your own property?
General guidance gets you informed. A survey makes it specific.
Every roof and household is different. A proper assessment connects the general principles in these guides to the actual property.