Before you sign a battery quote
Suggested questions for your installer. You may wish to ask for the answers in writing. Print this page or save it as a PDF, then use the answers in the home battery calculator.
Informational checklist only. It does not constitute technical, legal, tax or financial advice.
- What is the total price, including VAT, installation and anything extra? Put this in the calculator as the price you pay.
- Which rate of VAT have you applied to my quote, and for what installation date? HMRC's current rule for a battery installed without solar is 0% until 31 March 2027 and 5% after that. Ask the installer which rate they have applied.
- What is the usable capacity in kWh, and which figure does the quote refer to? Usable capacity is typically lower than nominal capacity.
- How much power can it charge and discharge at, in kW? A low figure can limit how much it charges in a short cheap-rate window.
- What is the round-trip efficiency, and is that figure AC to AC, including the inverter? It is the energy you get back for each unit you put in. Ask where the datasheet says so.
- Which electricity tariffs is this battery technically compatible with? Always check your eligibility directly with the energy supplier, because suppliers set and change their terms.
- What does the warranty cover, for how long, and what does it say about remaining capacity and any limit on use? Ask whether the inverter and the battery are covered separately.
- Does any notification or approval from your network operator apply, and who arranges it?
Write the answers next to each question. Keep the quote and the answers together.
General information only. Always use a qualified electrician. Rules and rates change.